Lock version of Docker Credential Helper in CI

* add aws secret handling

* make it look go-ish

* fix tests

* whitespace

* sleep a bit

.circleci/config.yml

@@ -3,8 +3,9 @@ version: 2.1
 jobs:
   canary:
     machine:
-      image: ubuntu-1604:202007-01
+      image: ubuntu-2004:202201-02
     working_directory: ~/docker-volume-backup
+    resource_class: large
     steps:
       - checkout
       - run:
@@ -19,6 +20,7 @@ jobs:
           name: Run tests
           working_directory: ~/docker-volume-backup/test
           command: |
+            export GPG_TTY=$(tty)
             ./test.sh canary
 
   build:
@@ -28,11 +30,13 @@ jobs:
           DOCKER_BUILDKIT: '1'
           DOCKER_CLI_EXPERIMENTAL: enabled
     working_directory: ~/docker-volume-backup
+    resource_class: large
     steps:
       - checkout
       - setup_remote_docker:
           version: 20.10.6
-      - docker/install-docker-credential-helper
+      - docker/install-docker-credential-helper:
+          release-tag: v0.6.4
       - docker/configure-docker-credentials-store
       - run:
           name: Push to Docker Hub
@@ -47,6 +51,7 @@ jobs:
             if [[ "$CIRCLE_TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
               # prerelease tags like `v2.0.0-alpha.1` should not be released as `latest`
               tag_args="$tag_args -t offen/docker-volume-backup:latest"
+              tag_args="$tag_args -t offen/docker-volume-backup:$(echo "$CIRCLE_TAG" | cut -d. -f1)"
             fi
             docker buildx build --platform linux/amd64,linux/arm64,linux/arm/v7 \
                $tag_args . --push
@@ -67,4 +72,4 @@ workflows:
               only: /^v.*/
 
 orbs:
-  docker: circleci/docker@1.0.1
+  docker: circleci/docker@2.1.4

.dockerignore

@@ -1 +1,7 @@
 test
+.github
+.circleci
+docs
+.editorconfig
+LICENSE
+README.md

.github/FUNDING.yml

@@ -0,0 +1,3 @@
+github: offen
+patreon: offen
+

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,28 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. ...
+2. ...
+3. ...
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Desktop (please complete the following information):**
+ - Image Version: [e.g. v2.21.0]
+ - Docker Version: [e.g. 20.10.17]
+ - Docker Compose Version (if applicable): [e.g. 1.29.2]
+
+**Additional context**
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

.github/ISSUE_TEMPLATE/support_request.md

@@ -0,0 +1,20 @@
+---
+name: Support request
+about: Ask for help
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**What are you trying to do?**
+A clear and concise description of what you are trying to do, but cannot get working.
+
+**What is your current configuration?**
+Add the full configuration you are using. Please redact out any real-world credentials.
+
+**Log output**
+Provide the full log output of your setup.
+
+**Additional context**
+Add any other context or screenshots about the support request here.

Dockerfile

@@ -1,20 +1,21 @@
 # Copyright 2021 - Offen Authors <hioffen@posteo.de>
 # SPDX-License-Identifier: MPL-2.0
 
-FROM golang:1.17-alpine as builder
+FROM golang:1.19-alpine as builder
 
 WORKDIR /app
-COPY go.mod go.sum ./
-COPY cmd/backup/main.go ./cmd/backup/main.go
-RUN go build -o backup cmd/backup/main.go
+COPY . .
+RUN go mod download
+WORKDIR /app/cmd/backup
+RUN go build -o backup .
 
-FROM alpine:3.14
+FROM alpine:3.16
 
 WORKDIR /root
 
-RUN apk add --update ca-certificates
+RUN apk add --no-cache ca-certificates
 
-COPY --from=builder /app/backup /usr/bin/backup
+COPY --from=builder /app/cmd/backup/backup /usr/bin/backup
 
 COPY ./entrypoint.sh /root/
 RUN chmod +x entrypoint.sh

README.md

@@ -1,9 +1,13 @@
+<a href="https://www.offen.dev/">
+    <img src="https://offen.github.io/press-kit/offen-material/gfx-GitHub-Offen-logo.svg" alt="Offen logo" title="Offen" width="150px"/>
+</a>
+
 # docker-volume-backup
 
 Backup Docker volumes locally or to any S3 compatible storage.
 
 The [offen/docker-volume-backup](https://hub.docker.com/r/offen/docker-volume-backup) Docker image can be used as a lightweight (below 15MB) sidecar container to an existing Docker setup.
-It handles __recurring or one-off backups of Docker volumes__ to a __local directory__ or __any S3 compatible storage__ (or both), and __rotates away old backups__ if configured. It also supports __encrypting your backups using GPG__ and __sending notifications for failed backup runs__.
+It handles __recurring or one-off backups of Docker volumes__ to a __local directory__, __any S3, WebDAV or SSH compatible storage (or any combination) and rotates away old backups__ if configured. It also supports __encrypting your backups using GPG__ and __sending notifications for failed backup runs__.
 
 <!-- MarkdownTOC -->
 
@@ -12,21 +16,35 @@ It handles __recurring or one-off backups of Docker volumes__ to a __local direc
   - [One-off backups using Docker CLI](#one-off-backups-using-docker-cli)
 - [Configuration reference](#configuration-reference)
 - [How to](#how-to)
-  - [Stopping containers during backup](#stopping-containers-during-backup)
+  - [Stop containers during backup](#stop-containers-during-backup)
   - [Automatically pruning old backups](#automatically-pruning-old-backups)
   - [Send email notifications on failed backup runs](#send-email-notifications-on-failed-backup-runs)
+  - [Customize notifications](#customize-notifications)
+  - [Run custom commands during the backup lifecycle](#run-custom-commands-during-the-backup-lifecycle)
   - [Encrypting your backup using GPG](#encrypting-your-backup-using-gpg)
   - [Restoring a volume from a backup](#restoring-a-volume-from-a-backup)
+  - [Set the timezone the container runs in](#set-the-timezone-the-container-runs-in)
   - [Using with Docker Swarm](#using-with-docker-swarm)
   - [Manually triggering a backup](#manually-triggering-a-backup)
+  - [Update deprecated email configuration](#update-deprecated-email-configuration)
+  - [Replace deprecated `BACKUP_FROM_SNAPSHOT` usage](#replace-deprecated-backup_from_snapshot-usage)
+  - [Replace deprecated `exec-pre` and `exec-post` labels](#replace-deprecated-exec-pre-and-exec-post-labels)
+  - [Using a custom Docker host](#using-a-custom-docker-host)
+  - [Run multiple backup schedules in the same container](#run-multiple-backup-schedules-in-the-same-container)
+  - [Define different retention schedules](#define-different-retention-schedules)
+  - [Use special characters in notification URLs](#use-special-characters-in-notification-urls)
 - [Recipes](#recipes)
   - [Backing up to AWS S3](#backing-up-to-aws-s3)
+  - [Backing up to Filebase](#backing-up-to-filebase)
   - [Backing up to MinIO](#backing-up-to-minio)
+  - [Backing up to WebDAV](#backing-up-to-webdav)
+  - [Backing up to SSH](#backing-up-to-ssh)
   - [Backing up locally](#backing-up-locally)
   - [Backing up to AWS S3 as well as locally](#backing-up-to-aws-s3-as-well-as-locally)
   - [Running on a custom cron schedule](#running-on-a-custom-cron-schedule)
   - [Rotating away backups that are older than 7 days](#rotating-away-backups-that-are-older-than-7-days)
   - [Encrypting your backups using GPG](#encrypting-your-backups-using-gpg)
+  - [Using mysqldump to prepare the backup](#using-mysqldump-to-prepare-the-backup)
   - [Running multiple instances in the same setup](#running-multiple-instances-in-the-same-setup)
 - [Differences to `futurice/docker-volume-backup`](#differences-to-futuricedocker-volume-backup)
 
@@ -71,7 +89,8 @@ services:
       - data:/backup/my-app-backup:ro
       # Mounting the Docker socket allows the script to stop and restart
       # the container during backup. You can omit this if you don't want
-      # to stop the container
+      # to stop the container. In case you need to proxy the socket, you can
+      # also provide a location by setting `DOCKER_HOST` in the container
       - /var/run/docker.sock:/var/run/docker.sock:ro
       # If you mount a local directory or volume to `/archive` a local
       # copy of the backup will be stored there. You can override the
@@ -93,7 +112,7 @@ docker run --rm \
   --env AWS_SECRET_ACCESS_KEY="<xxx>" \
   --env AWS_S3_BUCKET_NAME="<xxx>" \
   --entrypoint backup \
-  offen/docker-volume-backup:latest
+  offen/docker-volume-backup:v2
 ```
 
 Alternatively, pass a `--env-file` in order to use a full config as described below.
@@ -120,6 +139,44 @@ You can populate below template according to your requirements and use it as you
 
 # BACKUP_FILENAME="backup-%Y-%m-%dT%H-%M-%S.tar.gz"
 
+# Setting BACKUP_FILENAME_EXPAND to true allows for environment variable
+# placeholders in BACKUP_FILENAME, BACKUP_LATEST_SYMLINK and in
+# BACKUP_PRUNING_PREFIX that will get expanded at runtime,
+# e.g. `backup-$HOSTNAME-%Y-%m-%dT%H-%M-%S.tar.gz`. Expansion happens before
+# interpolating strftime tokens. It is disabled by default.
+# Please note that you will need to escape the `$` when providing the value
+# in a docker-compose.yml file, i.e. using $$VAR instead of $VAR.
+
+# BACKUP_FILENAME_EXPAND="true"
+
+# When storing local backups, a symlink to the latest backup can be created
+# in case a value is given for this key. This has no effect on remote backups.
+
+# BACKUP_LATEST_SYMLINK="backup.latest.tar.gz"
+
+# ************************************************************************
+# The BACKUP_FROM_SNAPSHOT option has been deprecated and will be removed
+# in the next major version. Please use exec-pre and exec-post
+# as documented below instead.
+# ************************************************************************
+# Whether to copy the content of backup folder before creating the tar archive.
+# In the rare scenario where the content of the source backup volume is continously
+# updating, but we do not wish to stop the container while performing the backup,
+# this setting can be used to ensure the integrity of the tar.gz file.
+
+# BACKUP_FROM_SNAPSHOT="false"
+
+# By default, the `/backup` directory inside the container will be backed up.
+# In case you need to use a custom location, set `BACKUP_SOURCES`.
+
+# BACKUP_SOURCES="/other/location"
+
+# When given, all files in BACKUP_SOURCES whose full path matches the given
+# regular expression will be excluded from the archive. Regular Expressions
+# can be used as from the Go standard library https://pkg.go.dev/regexp
+
+# BACKUP_EXCLUDE_REGEXP="\.log$"
+
 ########### BACKUP STORAGE
 
 # The name of the remote bucket that should be used for storing backups. If
@@ -127,6 +184,11 @@ You can populate below template according to your requirements and use it as you
 
 # AWS_S3_BUCKET_NAME="backup-bucket"
 
+# If you want to store the backup in a non-root location on your bucket
+# you can provide a path. The path must not contain a leading slash.
+
+# AWS_S3_PATH="my/backup/location"
+
 # Define credentials for authenticating against the backup storage and a bucket
 # name. Although all of these keys are `AWS`-prefixed, the setup can be used
 # with any S3 compatible storage.
@@ -134,6 +196,14 @@ You can populate below template according to your requirements and use it as you
 # AWS_ACCESS_KEY_ID="<xxx>"
 # AWS_SECRET_ACCESS_KEY="<xxx>"
 
+# It is possible to provide the keys in files, allowing to hide the sensitive data.
+# These values have a higher priority than the ones above, meaning if both are set
+# the values from the files will be used.
+# This option is most useful with Docker [secrets](https://docs.docker.com/engine/swarm/secrets/).
+
+# AWS_ACCESS_KEY_ID_FILE="/path/to/file"
+# AWS_SECRET_ACCESS_KEY_FILE="/path/to/file"
+
 # Instead of providing static credentials, you can also use IAM instance profiles
 # or similar to provide authentication. Some possible configuration options on AWS:
 # - EC2: http://169.254.169.254
@@ -142,7 +212,7 @@ You can populate below template according to your requirements and use it as you
 # AWS_IAM_ROLE_ENDPOINT="http://169.254.169.254"
 
 # This is the FQDN of your storage server, e.g. `storage.example.com`.
-# Do not set this when working against AWS S3 (the default value is 
+# Do not set this when working against AWS S3 (the default value is
 # `s3.amazonaws.com`). If you need to set a specific (non-https) protocol, you
 # will need to use the option below.
 
@@ -155,11 +225,76 @@ You can populate below template according to your requirements and use it as you
 # AWS_ENDPOINT_PROTO="https"
 
 # Setting this variable to `true` will disable verification of
-# SSL certificates. You shouldn't use this unless you use self-signed
-# certificates for your remote storage backend.
+# SSL certificates for AWS_ENDPOINT. You shouldn't use this unless you use
+# self-signed certificates for your remote storage backend. This can only be
+# used when AWS_ENDPOINT_PROTO is set to `https`.
 
 # AWS_ENDPOINT_INSECURE="true"
 
+# Setting this variable will change the S3 storage class header.
+# Defaults to "STANDARD", you can set this value according to your needs.
+
+# AWS_STORAGE_CLASS="GLACIER"
+
+# You can also backup files to any WebDAV server:
+
+# The URL of the remote WebDAV server
+
+# WEBDAV_URL="https://webdav.example.com"
+
+# The Directory to place the backups to on the WebDAV server.
+# If the path is not present on the server it will be created.
+
+# WEBDAV_PATH="/my/directory/"
+
+# The username for the WebDAV server
+
+# WEBDAV_USERNAME="user"
+
+# The password for the WebDAV server
+
+# WEBDAV_PASSWORD="password"
+
+# Setting this variable to `true` will disable verification of
+# SSL certificates for WEBDAV_URL. You shouldn't use this unless you use
+# self-signed certificates for your remote storage backend.
+
+# WEBDAV_URL_INSECURE="true"
+
+# You can also backup files to any SSH server:
+
+# The URL of the remote SSH server
+
+# SSH_HOST_NAME="server.local"
+
+# The port of the remote SSH server
+# Optional variable default value is `22`
+
+# SSH_PORT=2222
+
+# The Directory to place the backups to on the SSH server.
+
+# SSH_REMOTE_PATH="/my/directory/"
+
+# The username for the SSH server
+
+# SSH_USER="user"
+
+# The password for the SSH server
+
+# SSH_PASSWORD="password"
+
+# The private key path in container for SSH server
+# Default value: /root/.ssh/id_rsa
+# If file is mounted to /root/.ssh/id_rsa path it will be used. Non-RSA keys will
+# also work.
+
+# SSH_IDENTITY_FILE="/root/.ssh/id_rsa"
+
+# The passphrase for the identity file
+
+# SSH_IDENTITY_PASSPHRASE="pass"
+
 # In addition to storing backups remotely, you can also keep local copies.
 # Pass a container-local path to store your backups if needed. You also need to
 # mount a local folder or Docker volume into that location (`/archive`
@@ -221,11 +356,75 @@ You can populate below template according to your requirements and use it as you
 
 # BACKUP_STOP_CONTAINER_LABEL="service1"
 
-########### EMAIL NOTIFICATIONS ON FAILED BACKUP RUNS
+########### EXECUTING COMMANDS IN CONTAINERS PRE/POST BACKUP
 
-# In case SMTP credentials are provided, notification emails can be sent out on
-# failed backup runs. These emails will contain the start time, the error
-# message and all log output prior to the failure.
+# It is possible to define commands to be run in any container before and after
+# a backup is conducted. The commands themselves are defined in labels like
+# `docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump [options] > dump.sql'.
+# Several options exist for controlling this feature:
+
+# By default, any output of such a command is suppressed. If this value
+# is configured to be "true", command execution output will be forwarded to
+# the backup container's stdout and stderr.
+
+# EXEC_FORWARD_OUTPUT="true"
+
+# Without any further configuration, all commands defined in labels will be
+# run before and after a backup. If you need more fine grained control, you
+# can use this option to set a label that will be used for narrowing down
+# the set of eligible containers. When set, an eligible container will also need
+# to be labeled as `docker-volume-backup.exec-label=database`.
+
+# EXEC_LABEL="database"
+
+########### NOTIFICATIONS
+
+# Notifications (email, Slack, etc.) can be sent out when a backup run finishes.
+# Configuration is provided as a comma-separated list of URLs as consumed
+# by `shoutrrr`: https://containrrr.dev/shoutrrr/v0.5/services/overview/
+# The content of such notifications can be customized. Dedicated documentation
+# on how to do this can be found in the README. When providing multiple URLs or
+# an URL that contains a comma, the values can be URL encoded to avoid ambiguities.
+
+# The below URL demonstrates how to send an email using the provided SMTP
+# configuration and credentials.
+
+# NOTIFICATION_URLS=smtp://username:password@host:587/?fromAddress=sender@example.com&toAddresses=recipient@example.com
+
+# By default, notifications would only be sent out when a backup run fails
+# To receive notifications for every run, set `NOTIFICATION_LEVEL` to `info`
+# instead of the default `error`.
+
+# NOTIFICATION_LEVEL="error"
+
+########### DOCKER HOST
+
+# If you are interfacing with Docker via TCP you can set the Docker host here
+# instead of mounting the Docker socket as a volume. This is unset by default.
+
+# DOCKER_HOST="tcp://docker_socket_proxy:2375"
+
+########### LOCK_TIMEOUT
+
+# In the case of overlapping cron schedules run by the same container,
+# subsequent invocations will wait for previous runs to finish before starting.
+# By default, this will time out and fail in case the lock could not be acquired
+# after 60 minutes. In case you need to adjust this timeout, supply a duration
+# value as per https://pkg.go.dev/time#ParseDuration to `LOCK_TIMEOUT`
+
+# LOCK_TIMEOUT="60m"
+
+########### EMAIL NOTIFICATIONS
+
+# ************************************************************************
+# Providing notification configuration like this has been deprecated
+# and will be removed in the next major version. Please use NOTIFICATION_URLS
+# as documented above instead.
+# ************************************************************************
+
+# In case SMTP credentials are provided, notification emails can be sent out when
+# a backup run finished. These emails will contain the start time, the error
+# message on failure and all prior log output.
 
 # The recipient(s) of the notification. Supply a comma separated list
 # of adresses if you want to notify multiple recipients. If this is
@@ -246,9 +445,14 @@ You can populate below template according to your requirements and use it as you
 # EMAIL_SMTP_PORT="<port>"
 ```
 
+In case you encouter double quoted values in your configuration you might be running an [older version of `docker-compose`][compose-issue].
+You can work around this by either updating `docker-compose` or unquoting your configuration values.
+
+[compose-issue]: https://github.com/docker/compose/issues/2854
+
 ## How to
 
-### Stopping containers during backup
+### Stop containers during backup
 
 In many cases, it will be desirable to stop the services that are consuming the volume you want to backup in order to ensure data integrity.
 This image can automatically stop and restart containers and services (in case you are running Docker in Swarm mode).
@@ -266,7 +470,7 @@ services:
       - docker-volume-backup.stop-during-backup=service1
 
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
       BACKUP_STOP_CONTAINER_LABEL: service1
     volumes:
@@ -289,7 +493,7 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
       BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
       BACKUP_PRUNING_PREFIX: backup-
@@ -312,16 +516,104 @@ version: '3'
 
 services:
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
       # ... other configuration values go here
-      EMAIL_SMTP_HOST: "smtp.example.com"
-      EMAIL_SMTP_PASSWORD: "password"
-      EMAIL_SMTP_USERNAME: "username"
-      EMAIL_NOTIFICATION_SENDER: "noreply@example.com"
-      EMAIL_NOTIFICATION_RECIPIENT: "notifications@example.com"
+      NOTIFICATION_URLS=smtp://me:secret@smtp.example.com:587/?fromAddress=no-reply@example.com&toAddresses=you@example.com
 ```
 
+Notification backends other than email are also supported.
+Refer to the documentation of [shoutrrr][shoutrrr-docs] to find out about options and configuration.
+
+[shoutrrr-docs]: https://containrrr.dev/shoutrrr/v0.5/services/overview/
+
+### Customize notifications
+
+The title and body of the notifications can be easily tailored to your needs using [go templates](https://pkg.go.dev/text/template).
+Templates must be mounted inside the container in `/etc/dockervolumebackup/notifications.d/`: any file inside this directory will be parsed.
+
+The files have to define [nested templates](https://pkg.go.dev/text/template#hdr-Nested_template_definitions) in order to override the original values. An example:
+```
+{{ define "title_success" -}}
+✅ Successfully ran backup {{ .Config.BackupStopContainerLabel }}
+{{- end }}
+
+{{ define "body_success" -}}
+▶️ Start time: {{ .Stats.StartTime | formatTime }}
+⏹️ End time: {{ .Stats.EndTime | formatTime }}
+⌛ Took time: {{ .Stats.TookTime }}
+🛑 Stopped containers: {{ .Stats.Containers.Stopped }}/{{ .Stats.Containers.All }} ({{ .Stats.Containers.StopErrors }} errors)
+⚖️ Backup size: {{ .Stats.BackupFile.Size | formatBytesBin }} / {{ .Stats.BackupFile.Size | formatBytesDec }}
+🗑️ Pruned backups: {{ .Stats.Storages.Local.Pruned }}/{{ .Stats.Storages.Local.Total }} ({{ .Stats.Storages.Local.PruneErrors }} errors)
+{{- end }}
+```
+
+Overridable template names are: `title_success`, `body_success`, `title_failure`, `body_failure`.
+
+For a full list of available variables and functions, see [this page](https://github.com/offen/docker-volume-backup/blob/master/docs/NOTIFICATION-TEMPLATES.md).
+
+### Run custom commands during the backup lifecycle
+
+In certain scenarios it can be required to run specific commands before and after a backup is taken (e.g. dumping a database).
+When mounting the Docker socket into the `docker-volume-backup` container, you can define pre- and post-commands that will be run in the context of the target container (it is also possible to run commands inside the `docker-volume-backup` container itself using this feature).
+Such commands are defined by specifying the command in a `docker-volume-backup.[step]-[pre|post]` label where `step` can be any of the following phases of a backup lifecyle:
+
+- `archive` (the tar archive is created)
+- `process` (the tar archive is processed, e.g. encrypted - optional)
+- `copy` (the tar archive is copied to all configured storages)
+- `prune` (existing backups are pruned based on the defined ruleset - optional)
+
+Taking a database dump using `mysqldump` would look like this:
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  database:
+    image: mariadb
+    volumes:
+      - backup_data:/tmp/backups
+    labels:
+      - docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump --all-databases > /backups/dump.sql'
+
+volumes:
+  backup_data:
+```
+
+Due to Docker limitations, you currently cannot use any kind of redirection in these commands unless you pass the command to `/bin/sh -c` or similar.
+I.e. instead of using `echo "ok" > ok.txt` you will need to use `/bin/sh -c 'echo "ok" > ok.txt'`.
+
+If you need fine grained control about which container's commands are run, you can use the `EXEC_LABEL` configuration on your `docker-volume-backup` container:
+
+```yml
+version: '3'
+
+services:
+  database:
+    image: mariadb
+    volumes:
+      - backup_data:/tmp/backups
+    labels:
+      - docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump --all-databases > /tmp/volume/dump.sql'
+      - docker-volume-backup.exec-label=database
+
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      EXEC_LABEL: database
+    volumes:
+      - data:/backup/dump:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  backup_data:
+```
+
+
+The backup procedure is guaranteed to wait for all `pre` or `post` commands to finish before proceeding.
+However there are no guarantees about the order in which they are run, which could also happen concurrently.
+
 ### Encrypting your backup using GPG
 
 The image supports encrypting backups using GPG out of the box.
@@ -342,17 +634,58 @@ In case you need to restore a volume from a backup, the most straight forward pr
   ```console
   tar -C /tmp -xvf  backup.tar.gz
   ```
-- Using a temporary one-off container, mount the volume (the example assumes it's named `data`) and copy over the backup. Make sure you copy the correct path level (this depends on how you mount your volume into the backup container), you might need to strip some leading elements
+- Using a temporary once-off container, mount the volume (the example assumes it's named `data`) and copy over the backup. Make sure you copy the correct path level (this depends on how you mount your volume into the backup container), you might need to strip some leading elements
   ```console
-  docker run -d --name backup_restore -v data:/backup_restore alpine
-  docker cp /tmp/backup/data-backup backup_restore:/backup_restore
-  docker stop backup_restore
-  docker rm backup_restore
+  docker run -d --name temp_restore_container -v data:/backup_restore alpine
+  docker cp /tmp/backup/data-backup temp_restore_container:/backup_restore
+  docker stop temp_restore_container
+  docker rm temp_restore_container
   ```
-- Restart the container(s) that are using the volume 
+- Restart the container(s) that are using the volume
 
 Depending on your setup and the application(s) you are running, this might involve other steps to be taken still.
 
+---
+
+If you want to rollback an entire volume to an earlier backup snapshot (recommended for database volumes):
+
+- Trigger a manual backup if necessary (see `Manually triggering a backup`).
+- Stop the container(s) that are using the volume.
+- If volume was initially created using docker-compose, find out exact volume name using:
+  ```console
+  docker volume ls
+  ```
+- Remove existing volume (the example assumes it's named `data`):
+  ```console
+  docker volume rm data
+  ```
+- Create new volume with the same name and restore a snapshot:
+  ```console
+  docker run --rm -it -v data:/backup/my-app-backup -v /path/to/local_backups:/archive:ro alpine tar -xvzf /archive/full_backup_filename.tar.gz
+  ```
+- Restart the container(s) that are using the volume.
+
+### Set the timezone the container runs in
+
+By default a container based on this image will run in the UTC timezone.
+As the image is designed to be as small as possible, additional timezone data is not included.
+In case you want to run your cron rules in your local timezone (respecting DST and similar), you can mount your Docker host's `/etc/timezone` and `/etc/localtime` in read-only mode:
+
+```yml
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:v2
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /etc/timezone:/etc/timezone:ro
+      - /etc/localtime:/etc/localtime:ro
+
+volumes:
+  data:
+```
+
 ### Using with Docker Swarm
 
 By default, Docker Swarm will restart stopped containers automatically, even when manually stopped.
@@ -366,7 +699,7 @@ When running in Swarm mode, it's also advised to set a hard memory limit on your
 ```yml
 services:
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     deployment:
       resources:
         limits:
@@ -381,6 +714,178 @@ You can manually trigger a backup run outside of the defined cron schedule by ex
 docker exec <container_ref> backup
 ```
 
+### Update deprecated email configuration
+
+Starting with version 2.6.0, configuring email notifications using `EMAIL_*` keys has been deprecated.
+Instead of providing multiple values using multiple keys, you can now provide a single URL for `NOTIFICATION_URLS`.
+
+Before:
+```ini
+EMAIL_NOTIFICATION_RECIPIENT="you@example.com"
+EMAIL_NOTIFICATION_SENDER="no-reply@example.com"
+EMAIL_SMTP_HOST="posteo.de"
+EMAIL_SMTP_PASSWORD="secret"
+EMAIL_SMTP_USERNAME="me"
+EMAIL_SMTP_PORT="587"
+```
+
+After:
+```ini
+NOTIFICATION_URLS=smtp://me:secret@posteo.de:587/?fromAddress=no-reply@example.com&toAddresses=you@example.com
+```
+
+### Replace deprecated `BACKUP_FROM_SNAPSHOT` usage
+
+Starting with version 2.15.0, the `BACKUP_FROM_SNAPSHOT` feature has been deprecated.
+If you need to prepare your sources before the backup is taken, use `archive-pre`, `archive-post` and an intermediate volume:
+
+```yml
+version: '3'
+
+services:
+  my_app:
+    build: .
+    volumes:
+      - data:/var/my_app
+      - backup:/tmp/backup
+    labels:
+      - docker-volume-backup.archive-pre=cp -r /var/my_app /tmp/backup/my-app
+      - docker-volume-backup.archive-post=rm -rf /tmp/backup/my-app
+
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      BACKUP_SOURCES: /tmp/backup
+    volumes:
+      - backup:/backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+  backup:
+```
+
+### Replace deprecated `exec-pre` and `exec-post` labels
+
+Version 2.19.0 introduced the option to run labeled commands at multiple points in time during the backup lifecycle.
+In order to be able to use more obvious terminology in the new labels, the existing `exec-pre` and `exec-post` labels have been deprecated.
+If you want to emulate the existing behavior, all you need to do is change `exec-pre` to `archive-pre` and `exec-post` to `archive-post`:
+
+```diff
+    labels:
+-     - docker-volume-backup.exec-pre=cp -r /var/my_app /tmp/backup/my-app
++     - docker-volume-backup.archive-pre=cp -r /var/my_app /tmp/backup/my-app
+-     - docker-volume-backup.exec-post=rm -rf /tmp/backup/my-app
++     - docker-volume-backup.archive-post=rm -rf /tmp/backup/my-app
+```
+
+The `EXEC_LABEL` setting and the `docker-volume-backup.exec-label` label stay as is.
+Check the additional documentation on running commands during the backup lifecycle to find out about further possibilities.
+
+### Using a custom Docker host
+
+If you are interfacing with Docker via TCP, set `DOCKER_HOST` to the correct URL.
+```ini
+DOCKER_HOST=tcp://docker_socket_proxy:2375
+```
+
+In case you are using a socket proxy, it must support `GET` and `POST` requests to the `/containers` endpoint. If you are using Docker Swarm, it must also support the `/services` endpoint. If you are using pre/post backup commands, it must also support the `/exec` endpoint.
+
+### Run multiple backup schedules in the same container
+
+Multiple backup schedules with different configuration can be configured by mounting an arbitrary number of configuration files (using the `.env` format) into `/etc/dockervolumebackup/conf.d`:
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - ./configuration:/etc/dockervolumebackup/conf.d
+
+volumes:
+  data:
+```
+
+A separate cronjob will be created for each config file.
+If a configuration value is set both in the global environment as well as in the config file, the config file will take precedence.
+The `backup` command expects to run on an exclusive lock, so in case you provide the same or overlapping schedules in your cron expressions, the runs will still be executed serially, one after the other.
+The exact order of schedules that use the same cron expression is not specified.
+In case you need your schedules to overlap, you need to create a dedicated container for each schedule instead.
+When changing the configuration, you currently need to manually restart the container for the changes to take effect.
+
+Set `BACKUP_SOURCES` for each config file to control which subset of volume mounts gets backed up:
+
+```yml
+# With a volume configuration like this:
+volumes:
+  - /var/run/docker.sock:/var/run/docker.sock:ro
+  - ./configuration:/etc/dockervolumebackup/conf.d
+  - app1_data:/backup/app1_data:ro
+  - app2_data:/backup/app2_data:ro
+```
+
+```ini
+# In the 1st config file:
+BACKUP_SOURCES=/backup/app1_data
+
+# In the 2nd config file:
+BACKUP_SOURCES=/backup/app2_data
+```
+
+### Define different retention schedules
+
+If you want to manage backup retention on different schedules, the most straight forward approach is to define a dedicated configuration for retention rule using a different prefix in the `BACKUP_FILENAME` parameter and then run them on different cron schedules.
+
+For example, if you wanted to keep daily backups for 7 days, weekly backups for a month, and retain monthly backups forever, you could create three configuration files and mount them into `/etc/dockervolumebackup.d`:
+
+```ini
+# 01daily.conf
+BACKUP_FILENAME="daily-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
+# run every day at 2am
+BACKUP_CRON_EXPRESSION="0 2 * * *"
+BACKUP_PRUNING_PREFIX="daily-backup-"
+BACKUP_RETENTION_DAYS="7"
+```
+
+```ini
+# 02weekly.conf
+BACKUP_FILENAME="weekly-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
+# run every monday at 3am
+BACKUP_CRON_EXPRESSION="0 3 * * 1"
+BACKUP_PRUNING_PREFIX="weekly-backup-"
+BACKUP_RETENTION_DAYS="31"
+```
+
+```ini
+# 03monthly.conf
+BACKUP_FILENAME="monthly-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
+# run every 1st of a month at 4am
+BACKUP_CRON_EXPRESSION="0 4 1 * *"
+```
+
+Note that while it's possible to define colliding cron schedules for each of these configurations, you might need to adjust the value for `LOCK_TIMEOUT` in case your backups are large and might take longer than an hour.
+
+### Use special characters in notification URLs
+
+The value given to `NOTIFICATION_URLS` is a comma separated list of URLs.
+If such a URL contains special characters (e.g. commas) it needs to be URL encoded.
+To get an encoded version of your URL, you can use the CLI tool provided by `shoutrrr` (which is the library used for sending notifications):
+
+```
+docker run --rm -ti containrrr/shoutrrr generate [service]
+```
+
+where service is any of the [supported services][shoutrrr-docs], e.g. for SMTP:
+
+```
+docker run --rm -ti containrrr/shoutrrr generate smtp
+```
+
 ## Recipes
 
 This section lists configuration for some real-world use cases that you can mix and match according to your needs.
@@ -393,9 +898,9 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
     volumes:
@@ -406,6 +911,28 @@ volumes:
   data:
 ```
 
+### Backing up to Filebase
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      AWS_ENDPOINT: s3.filebase.com
+      AWS_S3_BUCKET_NAME: filebase-bucket
+      AWS_ACCESS_KEY_ID: FILEBASE-ACCESS-KEY
+      AWS_SECRET_ACCESS_KEY: FILEBASE-SECRET-KEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
 ### Backing up to MinIO
 
 ```yml
@@ -414,10 +941,10 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
       AWS_ENDPOINT: minio.example.com
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: MINIOACCESSKEY
       AWS_SECRET_ACCESS_KEY: MINIOSECRETKEY
     volumes:
@@ -428,6 +955,83 @@ volumes:
   data:
 ```
 
+
+### Backing up to MinIO (using Docker secrets)
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      AWS_ENDPOINT: minio.example.com
+      AWS_S3_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID_FILE: /run/secrets/minio_access_key
+      AWS_SECRET_ACCESS_KEY_FILE: /run/secrets/minio_secret_key
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+    secrets:
+      - minio_access_key
+      - minio_secret_key
+
+volumes:
+  data:
+
+secrets:
+  minio_access_key:
+    # ... define how secret is accessed
+  minio_secret_key:
+    # ... define how secret is accessed
+```
+
+### Backing up to WebDAV
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      WEBDAV_URL: https://webdav.mydomain.me
+      WEBDAV_PATH: /my/directory/
+      WEBDAV_USERNAME: user
+      WEBDAV_PASSWORD: password
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Backing up to SSH
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      SSH_HOST_NAME: server.local
+      SSH_PORT: 2222
+      SSH_USER: user
+      SSH_REMOTE_PATH: /data
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - /path/to/private_key:/root/.ssh/id_rsa
+
+volumes:
+  data:
+```
+
 ### Backing up locally
 
 ```yml
@@ -436,7 +1040,10 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
+    environment:
+      BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
+      BACKUP_LATEST_SYMLINK: backup-latest.tar.gz
     volumes:
       - data:/backup/my-app-backup:ro
       - /var/run/docker.sock:/var/run/docker.sock:ro
@@ -454,9 +1061,9 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
     volumes:
@@ -476,11 +1083,11 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
       # take a backup on every hour
       BACKUP_CRON_EXPRESSION: "0 * * * *"
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
     volumes:
@@ -499,9 +1106,9 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
       BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
@@ -523,9 +1130,9 @@ version: '3'
 services:
   # ... define other services using the `data` volume here
   backup:
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment:
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
       GPG_PASSPHRASE: somesecretstring
@@ -537,6 +1144,32 @@ volumes:
   data:
 ```
 
+### Using mysqldump to prepare the backup
+
+```yml
+version: '3'
+
+services:
+  database:
+    image: mariadb:latest
+    labels:
+      - docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump -psecret --all-databases > /tmp/dumps/dump.sql'
+    volumes:
+      - data:/tmp/dumps
+  backup:
+    image: offen/docker-volume-backup:v2
+    environment:
+      BACKUP_FILENAME: db.tar.gz
+      BACKUP_CRON_EXPRESSION: "0 2 * * *"
+    volumes:
+      - ./local:/archive
+      - data:/backup/data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+volumes:
+  data:
+```
+
 ### Running multiple instances in the same setup
 
 ```yml
@@ -545,10 +1178,10 @@ version: '3'
 services:
   # ... define other services using the `data_1` and `data_2` volumes here
   backup_1: &backup_service
-    image: offen/docker-volume-backup:latest
+    image: offen/docker-volume-backup:v2
     environment: &backup_environment
       BACKUP_CRON_EXPRESSION: "0 2 * * *"
-      AWS_BUCKET_NAME: backup-bucket
+      AWS_S3_BUCKET_NAME: backup-bucket
       AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
       AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
       # Label the container using the `data_1` volume as `docker-volume-backup.stop-during-backup=service1`
@@ -574,14 +1207,16 @@ volumes:
 
 ## Differences to `futurice/docker-volume-backup`
 
-This image is heavily inspired by the `futurice/docker-volume-backup`. We decided to publish this image as a simpler and more lightweight alternative because of the following requirements:
+This image is heavily inspired by `futurice/docker-volume-backup`. We decided to publish this image as a simpler and more lightweight alternative because of the following requirements:
 
 - The original image is based on `ubuntu` and requires additional tools, making it heavy.
 This version is roughly 1/25 in compressed size (it's ~12MB).
-- The original image uses a shell script, when this version is written in Go, which makes it easier to extend and maintain (more verbose too).
+- The original image uses a shell script, when this version is written in Go.
 - The original image proposed to handle backup rotation through AWS S3 lifecycle policies.
 This image adds the option to rotate away old backups through the same command so this functionality can also be offered for non-AWS storage backends like MinIO.
 Local copies of backups can also be pruned once they reach a certain age.
 - InfluxDB specific functionality from the original image was removed.
 - `arm64` and `arm/v7` architectures are supported.
 - Docker in Swarm mode is supported.
+- Notifications on finished backups are supported.
+- IAM authentication through instance profiles is supported.

cmd/backup/archive.go

@@ -0,0 +1,133 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+// Portions of this file are taken from package `targz`, Copyright (c) 2014 Fredrik Wallgren
+// Licensed under the MIT License: https://github.com/walle/targz/blob/57fe4206da5abf7dd3901b4af3891ec2f08c7b08/LICENSE
+
+package main
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+func createArchive(files []string, inputFilePath, outputFilePath string) error {
+	inputFilePath = stripTrailingSlashes(inputFilePath)
+	inputFilePath, outputFilePath, err := makeAbsolute(inputFilePath, outputFilePath)
+	if err != nil {
+		return fmt.Errorf("createArchive: error transposing given file paths: %w", err)
+	}
+	if err := os.MkdirAll(filepath.Dir(outputFilePath), 0755); err != nil {
+		return fmt.Errorf("createArchive: error creating output file path: %w", err)
+	}
+
+	if err := compress(files, outputFilePath, filepath.Dir(inputFilePath)); err != nil {
+		return fmt.Errorf("createArchive: error creating archive: %w", err)
+	}
+
+	return nil
+}
+
+func stripTrailingSlashes(path string) string {
+	if len(path) > 0 && path[len(path)-1] == '/' {
+		path = path[0 : len(path)-1]
+	}
+
+	return path
+}
+
+func makeAbsolute(inputFilePath, outputFilePath string) (string, string, error) {
+	inputFilePath, err := filepath.Abs(inputFilePath)
+	if err == nil {
+		outputFilePath, err = filepath.Abs(outputFilePath)
+	}
+
+	return inputFilePath, outputFilePath, err
+}
+
+func compress(paths []string, outFilePath, subPath string) error {
+	file, err := os.Create(outFilePath)
+	if err != nil {
+		return fmt.Errorf("compress: error creating out file: %w", err)
+	}
+
+	prefix := path.Dir(outFilePath)
+	gzipWriter := gzip.NewWriter(file)
+	tarWriter := tar.NewWriter(gzipWriter)
+
+	for _, p := range paths {
+		if err := writeTarGz(p, tarWriter, prefix); err != nil {
+			return fmt.Errorf("compress: error writing %s to archive: %w", p, err)
+		}
+	}
+
+	err = tarWriter.Close()
+	if err != nil {
+		return fmt.Errorf("compress: error closing tar writer: %w", err)
+	}
+
+	err = gzipWriter.Close()
+	if err != nil {
+		return fmt.Errorf("compress: error closing gzip writer: %w", err)
+	}
+
+	err = file.Close()
+	if err != nil {
+		return fmt.Errorf("compress: error closing file: %w", err)
+	}
+
+	return nil
+}
+
+func writeTarGz(path string, tarWriter *tar.Writer, prefix string) error {
+	fileInfo, err := os.Lstat(path)
+	if err != nil {
+		return fmt.Errorf("writeTarGz: error getting file infor for %s: %w", path, err)
+	}
+
+	if fileInfo.Mode()&os.ModeSocket == os.ModeSocket {
+		return nil
+	}
+
+	var link string
+	if fileInfo.Mode()&os.ModeSymlink == os.ModeSymlink {
+		var err error
+		if link, err = os.Readlink(path); err != nil {
+			return fmt.Errorf("writeTarGz: error resolving symlink %s: %w", path, err)
+		}
+	}
+
+	header, err := tar.FileInfoHeader(fileInfo, link)
+	if err != nil {
+		return fmt.Errorf("writeTarGz: error getting file info header: %w", err)
+	}
+	header.Name = strings.TrimPrefix(path, prefix)
+
+	err = tarWriter.WriteHeader(header)
+	if err != nil {
+		return fmt.Errorf("writeTarGz: error writing file info header: %w", err)
+	}
+
+	if !fileInfo.Mode().IsRegular() {
+		return nil
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("writeTarGz: error opening %s: %w", path, err)
+	}
+	defer file.Close()
+
+	_, err = io.Copy(tarWriter, file)
+	if err != nil {
+		return fmt.Errorf("writeTarGz: error copying %s to tar writer: %w", path, err)
+	}
+
+	return nil
+}

cmd/backup/config.go

@@ -0,0 +1,89 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"os"
+	"fmt"
+	"regexp"
+	"time"
+)
+
+// Config holds all configuration values that are expected to be set
+// by users.
+type Config struct {
+	AwsS3BucketName            string        `split_words:"true"`
+	AwsS3Path                  string        `split_words:"true"`
+	AwsEndpoint                string        `split_words:"true" default:"s3.amazonaws.com"`
+	AwsEndpointProto           string        `split_words:"true" default:"https"`
+	AwsEndpointInsecure        bool          `split_words:"true"`
+	AwsStorageClass            string        `split_words:"true"`
+	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
+	AwsAccessKeyIDFile         string        `envconfig:"AWS_ACCESS_KEY_ID_FILE"`
+	AwsSecretAccessKey         string        `split_words:"true"`
+	AwsSecretAccessKeyFile     string        `split_words:"true"`
+	AwsIamRoleEndpoint         string        `split_words:"true"`
+	BackupSources              string        `split_words:"true" default:"/backup"`
+	BackupFilename             string        `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.tar.gz"`
+	BackupFilenameExpand       bool          `split_words:"true"`
+	BackupLatestSymlink        string        `split_words:"true"`
+	BackupArchive              string        `split_words:"true" default:"/archive"`
+	BackupRetentionDays        int32         `split_words:"true" default:"-1"`
+	BackupPruningLeeway        time.Duration `split_words:"true" default:"1m"`
+	BackupPruningPrefix        string        `split_words:"true"`
+	BackupStopContainerLabel   string        `split_words:"true" default:"true"`
+	BackupFromSnapshot         bool          `split_words:"true"`
+	BackupExcludeRegexp        RegexpDecoder `split_words:"true"`
+	GpgPassphrase              string        `split_words:"true"`
+	NotificationURLs           []string      `envconfig:"NOTIFICATION_URLS"`
+	NotificationLevel          string        `split_words:"true" default:"error"`
+	EmailNotificationRecipient string        `split_words:"true"`
+	EmailNotificationSender    string        `split_words:"true" default:"noreply@nohost"`
+	EmailSMTPHost              string        `envconfig:"EMAIL_SMTP_HOST"`
+	EmailSMTPPort              int           `envconfig:"EMAIL_SMTP_PORT" default:"587"`
+	EmailSMTPUsername          string        `envconfig:"EMAIL_SMTP_USERNAME"`
+	EmailSMTPPassword          string        `envconfig:"EMAIL_SMTP_PASSWORD"`
+	WebdavUrl                  string        `split_words:"true"`
+	WebdavUrlInsecure          bool          `split_words:"true"`
+	WebdavPath                 string        `split_words:"true" default:"/"`
+	WebdavUsername             string        `split_words:"true"`
+	WebdavPassword             string        `split_words:"true"`
+	SSHHostName                string        `split_words:"true"`
+	SSHPort                    string        `split_words:"true" default:"22"`
+	SSHUser                    string        `split_words:"true"`
+	SSHPassword                string        `split_words:"true"`
+	SSHIdentityFile            string        `split_words:"true" default:"/root/.ssh/id_rsa"`
+	SSHIdentityPassphrase      string        `split_words:"true"`
+	SSHRemotePath              string        `split_words:"true"`
+	ExecLabel                  string        `split_words:"true"`
+	ExecForwardOutput          bool          `split_words:"true"`
+	LockTimeout                time.Duration `split_words:"true" default:"60m"`
+}
+
+func (c *Config) resolveSecret(envVar string, secretPath string) (string, error) {
+	if secretPath != "" {
+		data, err := os.ReadFile(secretPath)
+		if err != nil {
+			return "", fmt.Errorf("resolveSecret: error reading secret path: %w", err)
+		}
+		return string(data), nil
+	}
+	return envVar, nil
+}
+
+type RegexpDecoder struct {
+	Re *regexp.Regexp
+}
+
+func (r *RegexpDecoder) Decode(v string) error {
+	if v == "" {
+		return nil
+	}
+	re, err := regexp.Compile(v)
+	if err != nil {
+		return fmt.Errorf("config: error compiling given regexp `%s`: %w", v, err)
+	}
+	*r = RegexpDecoder{Re: re}
+	return nil
+}

cmd/backup/exec.go

@@ -0,0 +1,199 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+// Portions of this file are taken and adapted from `moby`, Copyright 2012-2017 Docker, Inc.
+// Licensed under the Apache 2.0 License: https://github.com/moby/moby/blob/8e610b2b55bfd1bfa9436ab110d311f5e8a74dcb/LICENSE
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/cosiner/argv"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/filters"
+	"github.com/docker/docker/pkg/stdcopy"
+	"golang.org/x/sync/errgroup"
+)
+
+func (s *script) exec(containerRef string, command string) ([]byte, []byte, error) {
+	args, _ := argv.Argv(command, nil, nil)
+	execID, err := s.cli.ContainerExecCreate(context.Background(), containerRef, types.ExecConfig{
+		Cmd:          args[0],
+		AttachStdin:  true,
+		AttachStderr: true,
+	})
+	if err != nil {
+		return nil, nil, fmt.Errorf("exec: error creating container exec: %w", err)
+	}
+
+	resp, err := s.cli.ContainerExecAttach(context.Background(), execID.ID, types.ExecStartCheck{})
+	if err != nil {
+		return nil, nil, fmt.Errorf("exec: error attaching container exec: %w", err)
+	}
+	defer resp.Close()
+
+	var outBuf, errBuf bytes.Buffer
+	outputDone := make(chan error)
+
+	go func() {
+		_, err := stdcopy.StdCopy(&outBuf, &errBuf, resp.Reader)
+		outputDone <- err
+	}()
+
+	select {
+	case err := <-outputDone:
+		if err != nil {
+			return nil, nil, fmt.Errorf("exec: error demultiplexing output: %w", err)
+		}
+		break
+	}
+
+	stdout, err := ioutil.ReadAll(&outBuf)
+	if err != nil {
+		return nil, nil, fmt.Errorf("exec: error reading stdout: %w", err)
+	}
+	stderr, err := ioutil.ReadAll(&errBuf)
+	if err != nil {
+		return nil, nil, fmt.Errorf("exec: error reading stderr: %w", err)
+	}
+
+	res, err := s.cli.ContainerExecInspect(context.Background(), execID.ID)
+	if err != nil {
+		return nil, nil, fmt.Errorf("exec: error inspecting container exec: %w", err)
+	}
+
+	if res.ExitCode > 0 {
+		return stdout, stderr, fmt.Errorf("exec: running command exited %d", res.ExitCode)
+	}
+
+	return stdout, stderr, nil
+}
+
+func (s *script) runLabeledCommands(label string) error {
+	f := []filters.KeyValuePair{
+		{Key: "label", Value: label},
+	}
+	if s.c.ExecLabel != "" {
+		f = append(f, filters.KeyValuePair{
+			Key:   "label",
+			Value: fmt.Sprintf("docker-volume-backup.exec-label=%s", s.c.ExecLabel),
+		})
+	}
+	containersWithCommand, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+		Quiet:   true,
+		Filters: filters.NewArgs(f...),
+	})
+	if err != nil {
+		return fmt.Errorf("runLabeledCommands: error querying for containers: %w", err)
+	}
+
+	var hasDeprecatedContainers bool
+	if label == "docker-volume-backup.archive-pre" {
+		f[0] = filters.KeyValuePair{
+			Key:   "label",
+			Value: "docker-volume-backup.exec-pre",
+		}
+		deprecatedContainers, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+			Quiet:   true,
+			Filters: filters.NewArgs(f...),
+		})
+		if err != nil {
+			return fmt.Errorf("runLabeledCommands: error querying for containers: %w", err)
+		}
+		if len(deprecatedContainers) != 0 {
+			hasDeprecatedContainers = true
+			containersWithCommand = append(containersWithCommand, deprecatedContainers...)
+		}
+	}
+
+	if label == "docker-volume-backup.archive-post" {
+		f[0] = filters.KeyValuePair{
+			Key:   "label",
+			Value: "docker-volume-backup.exec-post",
+		}
+		deprecatedContainers, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+			Quiet:   true,
+			Filters: filters.NewArgs(f...),
+		})
+		if err != nil {
+			return fmt.Errorf("runLabeledCommands: error querying for containers: %w", err)
+		}
+		if len(deprecatedContainers) != 0 {
+			hasDeprecatedContainers = true
+			containersWithCommand = append(containersWithCommand, deprecatedContainers...)
+		}
+	}
+
+	if len(containersWithCommand) == 0 {
+		return nil
+	}
+
+	if hasDeprecatedContainers {
+		s.logger.Warn(
+			"Using `docker-volume-backup.exec-pre` and `docker-volume-backup.exec-post` labels has been deprecated and will be removed in the next major version.",
+		)
+		s.logger.Warn(
+			"Please use other `-pre` and `-post` labels instead. Refer to the README for an upgrade guide.",
+		)
+	}
+
+	g := new(errgroup.Group)
+
+	for _, container := range containersWithCommand {
+		c := container
+		g.Go(func() error {
+			cmd, ok := c.Labels[label]
+			if !ok && label == "docker-volume-backup.archive-pre" {
+				cmd, _ = c.Labels["docker-volume-backup.exec-pre"]
+			} else if !ok && label == "docker-volume-backup.archive-post" {
+				cmd, _ = c.Labels["docker-volume-backup.exec-post"]
+			}
+
+			s.logger.Infof("Running %s command %s for container %s", label, cmd, strings.TrimPrefix(c.Names[0], "/"))
+			stdout, stderr, err := s.exec(c.ID, cmd)
+			if s.c.ExecForwardOutput {
+				os.Stderr.Write(stderr)
+				os.Stdout.Write(stdout)
+			}
+			if err != nil {
+				return fmt.Errorf("runLabeledCommands: error executing command: %w", err)
+			}
+			return nil
+		})
+	}
+
+	if err := g.Wait(); err != nil {
+		return fmt.Errorf("runLabeledCommands: error from errgroup: %w", err)
+	}
+	return nil
+}
+
+type lifecyclePhase string
+
+const (
+	lifecyclePhaseArchive lifecyclePhase = "archive"
+	lifecyclePhaseProcess lifecyclePhase = "process"
+	lifecyclePhaseCopy    lifecyclePhase = "copy"
+	lifecyclePhasePrune   lifecyclePhase = "prune"
+)
+
+func (s *script) withLabeledCommands(step lifecyclePhase, cb func() error) func() error {
+	if s.cli == nil {
+		return cb
+	}
+	return func() error {
+		if err := s.runLabeledCommands(fmt.Sprintf("docker-volume-backup.%s-pre", step)); err != nil {
+			return fmt.Errorf("withLabeledCommands: %s: error running pre commands: %w", step, err)
+		}
+		defer func() {
+			s.must(s.runLabeledCommands(fmt.Sprintf("docker-volume-backup.%s-post", step)))
+		}()
+		return cb()
+	}
+}

cmd/backup/hooks.go

@@ -0,0 +1,58 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"fmt"
+	"sort"
+
+	"github.com/offen/docker-volume-backup/internal/utilities"
+)
+
+// hook contains a queued action that can be trigger them when the script
+// reaches a certain point (e.g. unsuccessful backup)
+type hook struct {
+	level  hookLevel
+	action func(err error) error
+}
+
+type hookLevel int
+
+const (
+	hookLevelPlumbing hookLevel = iota
+	hookLevelError
+	hookLevelInfo
+)
+
+var hookLevels = map[string]hookLevel{
+	"info":  hookLevelInfo,
+	"error": hookLevelError,
+}
+
+// registerHook adds the given action at the given level.
+func (s *script) registerHook(level hookLevel, action func(err error) error) {
+	s.hooks = append(s.hooks, hook{level, action})
+}
+
+// runHooks runs all hooks that have been registered using the
+// given levels in the defined ordering. In case executing a hook returns an
+// error, the following hooks will still be run before the function returns.
+func (s *script) runHooks(err error) error {
+	sort.SliceStable(s.hooks, func(i, j int) bool {
+		return s.hooks[i].level < s.hooks[j].level
+	})
+	var actionErrors []error
+	for _, hook := range s.hooks {
+		if hook.level > s.hookLevel {
+			continue
+		}
+		if actionErr := hook.action(err); actionErr != nil {
+			actionErrors = append(actionErrors, fmt.Errorf("runHooks: error running hook: %w", actionErr))
+		}
+	}
+	if len(actionErrors) != 0 {
+		return utilities.Join(actionErrors...)
+	}
+	return nil
+}

cmd/backup/lock.go

@@ -0,0 +1,58 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/gofrs/flock"
+)
+
+// lock opens a lockfile at the given location, keeping it locked until the
+// caller invokes the returned release func. In case the lock is currently blocked
+// by another execution, it will repeatedly retry until the lock is available
+// or the given timeout is exceeded.
+func (s *script) lock(lockfile string) (func() error, error) {
+	start := time.Now()
+	defer func() {
+		s.stats.LockedTime = time.Now().Sub(start)
+	}()
+
+	retry := time.NewTicker(5 * time.Second)
+	defer retry.Stop()
+	deadline := time.NewTimer(s.c.LockTimeout)
+	defer deadline.Stop()
+
+	fileLock := flock.New(lockfile)
+
+	for {
+		acquired, err := fileLock.TryLock()
+		if err != nil {
+			return noop, fmt.Errorf("lock: error trying to lock: %w", err)
+		}
+		if acquired {
+			if s.encounteredLock {
+				s.logger.Info("Acquired exclusive lock on subsequent attempt, ready to continue.")
+			}
+			return fileLock.Unlock, nil
+		}
+
+		if !s.encounteredLock {
+			s.logger.Infof(
+				"Exclusive lock was not available on first attempt. Will retry until it becomes available or the timeout of %s is exceeded.",
+				s.c.LockTimeout,
+			)
+			s.encounteredLock = true
+		}
+
+		select {
+		case <-retry.C:
+			continue
+		case <-deadline.C:
+			return noop, errors.New("lock: timed out waiting for lockfile to become available")
+		}
+	}
+}

cmd/backup/main.go

@@ -1,649 +1,58 @@
-// Copyright 2021 - Offen Authors <hioffen@posteo.de>
+// Copyright 2021-2022 - Offen Authors <hioffen@posteo.de>
 // SPDX-License-Identifier: MPL-2.0
 
 package main
 
 import (
-	"bytes"
-	"context"
-	"errors"
-	"fmt"
-	"io"
 	"os"
-	"path"
-	"path/filepath"
-	"strings"
-	"time"
-
-	"github.com/docker/docker/api/types"
-	"github.com/docker/docker/api/types/filters"
-	"github.com/docker/docker/api/types/swarm"
-	"github.com/docker/docker/client"
-	"github.com/go-gomail/gomail"
-	"github.com/gofrs/flock"
-	"github.com/kelseyhightower/envconfig"
-	"github.com/leekchan/timeutil"
-	"github.com/m90/targz"
-	"github.com/minio/minio-go/v7"
-	"github.com/minio/minio-go/v7/pkg/credentials"
-	"github.com/sirupsen/logrus"
-	"golang.org/x/crypto/openpgp"
 )
 
 func main() {
-	unlock := lock("/var/lock/dockervolumebackup.lock")
-	defer unlock()
-
 	s, err := newScript()
 	if err != nil {
 		panic(err)
 	}
 
+	unlock, err := s.lock("/var/lock/dockervolumebackup.lock")
+	defer unlock()
+	s.must(err)
+
 	defer func() {
-		if err := recover(); err != nil {
-			if e, ok := err.(error); ok && strings.Contains(e.Error(), msgBackupFailed) {
+		if pArg := recover(); pArg != nil {
+			if err, ok := pArg.(error); ok {
+				if hookErr := s.runHooks(err); hookErr != nil {
+					s.logger.Errorf("An error occurred calling the registered hooks: %s", hookErr)
+				}
 				os.Exit(1)
 			}
-			panic(err)
+			panic(pArg)
 		}
+
+		if err := s.runHooks(nil); err != nil {
+			s.logger.Errorf(
+				"Backup procedure ran successfully, but an error ocurred calling the registered hooks: %v",
+				err,
+			)
+			os.Exit(1)
+		}
+		s.logger.Info("Finished running backup tasks.")
 	}()
 
-	s.must(func() error {
+	s.must(s.withLabeledCommands(lifecyclePhaseArchive, func() error {
 		restartContainers, err := s.stopContainers()
+		// The mechanism for restarting containers is not using hooks as it
+		// should happen as soon as possible (i.e. before uploading backups or
+		// similar).
 		defer func() {
 			s.must(restartContainers())
 		}()
 		if err != nil {
 			return err
 		}
-		return s.takeBackup()
-	}())
+		return s.createArchive()
+	})())
 
-	s.must(func() error {
-		defer func() {
-			s.must(s.removeArtifacts())
-		}()
-		s.must(s.encryptBackup())
-		return s.copyBackup()
-	}())
-
-	s.must(s.pruneOldBackups())
-	s.logger.Info("Finished running backup tasks.")
+	s.must(s.withLabeledCommands(lifecyclePhaseProcess, s.encryptArchive)())
+	s.must(s.withLabeledCommands(lifecyclePhaseCopy, s.copyArchive)())
+	s.must(s.withLabeledCommands(lifecyclePhasePrune, s.pruneBackups)())
 }
-
-// script holds all the stateful information required to orchestrate a
-// single backup run.
-type script struct {
-	cli    *client.Client
-	mc     *minio.Client
-	logger *logrus.Logger
-	hooks  []hook
-
-	start  time.Time
-	file   string
-	output *bytes.Buffer
-
-	c *config
-}
-
-type config struct {
-	BackupSources              string        `split_words:"true" default:"/backup"`
-	BackupFilename             string        `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.tar.gz"`
-	BackupArchive              string        `split_words:"true" default:"/archive"`
-	BackupRetentionDays        int32         `split_words:"true" default:"-1"`
-	BackupPruningLeeway        time.Duration `split_words:"true" default:"1m"`
-	BackupPruningPrefix        string        `split_words:"true"`
-	BackupStopContainerLabel   string        `split_words:"true" default:"true"`
-	AwsS3BucketName            string        `split_words:"true"`
-	AwsEndpoint                string        `split_words:"true" default:"s3.amazonaws.com"`
-	AwsEndpointProto           string        `split_words:"true" default:"https"`
-	AwsEndpointInsecure        bool          `split_words:"true"`
-	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
-	AwsSecretAccessKey         string        `split_words:"true"`
-	AwsIamRoleEndpoint         string        `split_words:"true"`
-	GpgPassphrase              string        `split_words:"true"`
-	EmailNotificationRecipient string        `split_words:"true"`
-	EmailNotificationSender    string        `split_words:"true" default:"noreply@nohost"`
-	EmailSMTPHost              string        `envconfig:"EMAIL_SMTP_HOST"`
-	EmailSMTPPort              int           `envconfig:"EMAIL_SMTP_PORT" default:"587"`
-	EmailSMTPUsername          string        `envconfig:"EMAIL_SMTP_USERNAME"`
-	EmailSMTPPassword          string        `envconfig:"EMAIL_SMTP_PASSWORD"`
-}
-
-var msgBackupFailed = "backup run failed"
-
-// newScript creates all resources needed for the script to perform actions against
-// remote resources like the Docker engine or remote storage locations. All
-// reading from env vars or other configuration sources is expected to happen
-// in this method.
-func newScript() (*script, error) {
-	stdOut, logBuffer := buffer(os.Stdout)
-	s := &script{
-		c: &config{},
-		logger: &logrus.Logger{
-			Out:       stdOut,
-			Formatter: new(logrus.TextFormatter),
-			Hooks:     make(logrus.LevelHooks),
-			Level:     logrus.InfoLevel,
-		},
-		start:  time.Now(),
-		output: logBuffer,
-	}
-
-	if err := envconfig.Process("", s.c); err != nil {
-		return nil, fmt.Errorf("newScript: failed to process configuration values: %w", err)
-	}
-
-	s.file = path.Join("/tmp", s.c.BackupFilename)
-
-	_, err := os.Stat("/var/run/docker.sock")
-	if !os.IsNotExist(err) {
-		cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
-		if err != nil {
-			return nil, fmt.Errorf("newScript: failed to create docker client")
-		}
-		s.cli = cli
-	}
-
-	if s.c.AwsS3BucketName != "" {
-		var creds *credentials.Credentials
-		if s.c.AwsAccessKeyID != "" && s.c.AwsSecretAccessKey != "" {
-			creds = credentials.NewStaticV4(
-				s.c.AwsAccessKeyID,
-				s.c.AwsSecretAccessKey,
-				"",
-			)
-		} else if s.c.AwsIamRoleEndpoint != "" {
-			creds = credentials.NewIAM(s.c.AwsIamRoleEndpoint)
-		} else {
-			return nil, errors.New("newScript: AWS_S3_BUCKET_NAME is defined, but no credentials were provided")
-		}
-
-		mc, err := minio.New(s.c.AwsEndpoint, &minio.Options{
-			Creds:  creds,
-			Secure: !s.c.AwsEndpointInsecure && s.c.AwsEndpointProto == "https",
-		})
-		if err != nil {
-			return nil, fmt.Errorf("newScript: error setting up minio client: %w", err)
-		}
-		s.mc = mc
-	}
-
-	if s.c.EmailNotificationRecipient != "" {
-		s.hooks = append(s.hooks, hook{hookLevelFailure, func(err error, start time.Time, logOutput string) error {
-			mailer := gomail.NewDialer(
-				s.c.EmailSMTPHost, s.c.EmailSMTPPort, s.c.EmailSMTPUsername, s.c.EmailSMTPPassword,
-			)
-
-			subject := fmt.Sprintf(
-				"Failure running docker-volume-backup at %s", start.Format(time.RFC3339),
-			)
-			body := fmt.Sprintf(
-				"Running docker-volume-backup failed with error: %s\n\nLog output of the failed run was:\n\n%s\n", err, logOutput,
-			)
-
-			message := gomail.NewMessage()
-			message.SetHeader("From", s.c.EmailNotificationSender)
-			message.SetHeader("To", s.c.EmailNotificationRecipient)
-			message.SetHeader("Subject", subject)
-			message.SetBody("text/plain", body)
-			return mailer.DialAndSend(message)
-		}})
-	}
-
-	return s, nil
-}
-
-var noop = func() error { return nil }
-
-// stopContainers stops all Docker containers that are marked as to being
-// stopped during the backup and returns a function that can be called to
-// restart everything that has been stopped.
-func (s *script) stopContainers() (func() error, error) {
-	if s.cli == nil {
-		return noop, nil
-	}
-
-	allContainers, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
-		Quiet: true,
-	})
-	if err != nil {
-		return noop, fmt.Errorf("stopContainersAndRun: error querying for containers: %w", err)
-	}
-
-	containerLabel := fmt.Sprintf(
-		"docker-volume-backup.stop-during-backup=%s",
-		s.c.BackupStopContainerLabel,
-	)
-	containersToStop, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
-		Quiet: true,
-		Filters: filters.NewArgs(filters.KeyValuePair{
-			Key:   "label",
-			Value: containerLabel,
-		}),
-	})
-
-	if err != nil {
-		return noop, fmt.Errorf("stopContainersAndRun: error querying for containers to stop: %w", err)
-	}
-
-	if len(containersToStop) == 0 {
-		return noop, nil
-	}
-
-	s.logger.Infof(
-		"Stopping %d container(s) labeled `%s` out of %d running container(s).",
-		len(containersToStop),
-		containerLabel,
-		len(allContainers),
-	)
-
-	var stoppedContainers []types.Container
-	var stopErrors []error
-	for _, container := range containersToStop {
-		if err := s.cli.ContainerStop(context.Background(), container.ID, nil); err != nil {
-			stopErrors = append(stopErrors, err)
-		} else {
-			stoppedContainers = append(stoppedContainers, container)
-		}
-	}
-
-	var stopError error
-	if len(stopErrors) != 0 {
-		stopError = fmt.Errorf(
-			"stopContainersAndRun: %d error(s) stopping containers: %w",
-			len(stopErrors),
-			join(stopErrors...),
-		)
-	}
-
-	return func() error {
-		servicesRequiringUpdate := map[string]struct{}{}
-
-		var restartErrors []error
-		for _, container := range stoppedContainers {
-			if swarmServiceName, ok := container.Labels["com.docker.swarm.service.name"]; ok {
-				servicesRequiringUpdate[swarmServiceName] = struct{}{}
-				continue
-			}
-			if err := s.cli.ContainerStart(context.Background(), container.ID, types.ContainerStartOptions{}); err != nil {
-				restartErrors = append(restartErrors, err)
-			}
-		}
-
-		if len(servicesRequiringUpdate) != 0 {
-			services, _ := s.cli.ServiceList(context.Background(), types.ServiceListOptions{})
-			for serviceName := range servicesRequiringUpdate {
-				var serviceMatch swarm.Service
-				for _, service := range services {
-					if service.Spec.Name == serviceName {
-						serviceMatch = service
-						break
-					}
-				}
-				if serviceMatch.ID == "" {
-					return fmt.Errorf("stopContainersAndRun: couldn't find service with name %s", serviceName)
-				}
-				serviceMatch.Spec.TaskTemplate.ForceUpdate = 1
-				_, err := s.cli.ServiceUpdate(
-					context.Background(), serviceMatch.ID,
-					serviceMatch.Version, serviceMatch.Spec, types.ServiceUpdateOptions{},
-				)
-				if err != nil {
-					restartErrors = append(restartErrors, err)
-				}
-			}
-		}
-
-		if len(restartErrors) != 0 {
-			return fmt.Errorf(
-				"stopContainersAndRun: %d error(s) restarting containers and services: %w",
-				len(restartErrors),
-				join(restartErrors...),
-			)
-		}
-		s.logger.Infof(
-			"Restarted %d container(s) and the matching service(s).",
-			len(stoppedContainers),
-		)
-		return nil
-	}, stopError
-}
-
-// takeBackup creates a tar archive of the configured backup location and
-// saves it to disk.
-func (s *script) takeBackup() error {
-	s.file = timeutil.Strftime(&s.start, s.file)
-	if err := targz.Compress(s.c.BackupSources, s.file); err != nil {
-		return fmt.Errorf("takeBackup: error compressing backup folder: %w", err)
-	}
-	s.logger.Infof("Created backup of `%s` at `%s`.", s.c.BackupSources, s.file)
-	return nil
-}
-
-// encryptBackup encrypts the backup file using PGP and the configured passphrase.
-// In case no passphrase is given it returns early, leaving the backup file
-// untouched.
-func (s *script) encryptBackup() error {
-	if s.c.GpgPassphrase == "" {
-		return nil
-	}
-	defer os.Remove(s.file)
-
-	gpgFile := fmt.Sprintf("%s.gpg", s.file)
-	outFile, err := os.Create(gpgFile)
-	defer outFile.Close()
-	if err != nil {
-		return fmt.Errorf("encryptBackup: error opening out file: %w", err)
-	}
-
-	_, name := path.Split(s.file)
-	dst, err := openpgp.SymmetricallyEncrypt(outFile, []byte(s.c.GpgPassphrase), &openpgp.FileHints{
-		IsBinary: true,
-		FileName: name,
-	}, nil)
-	defer dst.Close()
-	if err != nil {
-		return fmt.Errorf("encryptBackup: error encrypting backup file: %w", err)
-	}
-
-	src, err := os.Open(s.file)
-	if err != nil {
-		return fmt.Errorf("encryptBackup: error opening backup file %s: %w", s.file, err)
-	}
-
-	if _, err := io.Copy(dst, src); err != nil {
-		return fmt.Errorf("encryptBackup: error writing ciphertext to file: %w", err)
-	}
-
-	s.file = gpgFile
-	s.logger.Infof("Encrypted backup using given passphrase, saving as `%s`.", s.file)
-	return nil
-}
-
-// copyBackup makes sure the backup file is copied to both local and remote locations
-// as per the given configuration.
-func (s *script) copyBackup() error {
-	_, name := path.Split(s.file)
-	if s.mc != nil {
-		_, err := s.mc.FPutObject(context.Background(), s.c.AwsS3BucketName, name, s.file, minio.PutObjectOptions{
-			ContentType: "application/tar+gzip",
-		})
-		if err != nil {
-			return fmt.Errorf("copyBackup: error uploading backup to remote storage: %w", err)
-		}
-		s.logger.Infof("Uploaded a copy of backup `%s` to bucket `%s`.", s.file, s.c.AwsS3BucketName)
-	}
-
-	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
-		if err := copy(s.file, path.Join(s.c.BackupArchive, name)); err != nil {
-			return fmt.Errorf("copyBackup: error copying file to local archive: %w", err)
-		}
-		s.logger.Infof("Stored copy of backup `%s` in local archive `%s`.", s.file, s.c.BackupArchive)
-	}
-	return nil
-}
-
-// removeArtifacts removes the backup file from disk.
-func (s *script) removeArtifacts() error {
-	_, err := os.Stat(s.file)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return fmt.Errorf("removeArtifacts: error calling stat on file %s: %w", s.file, err)
-	}
-	if err := os.Remove(s.file); err != nil {
-		return fmt.Errorf("removeArtifacts: error removing file %s: %w", s.file, err)
-	}
-	s.logger.Infof("Removed local artifacts %s.", s.file)
-	return nil
-}
-
-// pruneOldBackups rotates away backups from local and remote storages using
-// the given configuration. In case the given configuration would delete all
-// backups, it does nothing instead.
-func (s *script) pruneOldBackups() error {
-	if s.c.BackupRetentionDays < 0 {
-		return nil
-	}
-
-	if s.c.BackupPruningLeeway != 0 {
-		s.logger.Infof("Sleeping for %s before pruning backups.", s.c.BackupPruningLeeway)
-		time.Sleep(s.c.BackupPruningLeeway)
-	}
-
-	deadline := time.Now().AddDate(0, 0, -int(s.c.BackupRetentionDays))
-
-	if s.mc != nil {
-		candidates := s.mc.ListObjects(context.Background(), s.c.AwsS3BucketName, minio.ListObjectsOptions{
-			WithMetadata: true,
-			Prefix:       s.c.BackupPruningPrefix,
-		})
-
-		var matches []minio.ObjectInfo
-		var lenCandidates int
-		for candidate := range candidates {
-			lenCandidates++
-			if candidate.Err != nil {
-				return fmt.Errorf(
-					"pruneOldBackups: error looking up candidates from remote storage: %w",
-					candidate.Err,
-				)
-			}
-			if candidate.LastModified.Before(deadline) {
-				matches = append(matches, candidate)
-			}
-		}
-
-		if len(matches) != 0 && len(matches) != lenCandidates {
-			objectsCh := make(chan minio.ObjectInfo)
-			go func() {
-				for _, match := range matches {
-					objectsCh <- match
-				}
-				close(objectsCh)
-			}()
-			errChan := s.mc.RemoveObjects(context.Background(), s.c.AwsS3BucketName, objectsCh, minio.RemoveObjectsOptions{})
-			var removeErrors []error
-			for result := range errChan {
-				if result.Err != nil {
-					removeErrors = append(removeErrors, result.Err)
-				}
-			}
-
-			if len(removeErrors) != 0 {
-				return fmt.Errorf(
-					"pruneOldBackups: %d error(s) removing files from remote storage: %w",
-					len(removeErrors),
-					join(removeErrors...),
-				)
-			}
-			s.logger.Infof(
-				"Pruned %d out of %d remote backup(s) as their age exceeded the configured retention period of %d days.",
-				len(matches),
-				lenCandidates,
-				s.c.BackupRetentionDays,
-			)
-		} else if len(matches) != 0 && len(matches) == lenCandidates {
-			s.logger.Warnf(
-				"The current configuration would delete all %d remote backup copies.",
-				len(matches),
-			)
-			s.logger.Warn("Refusing to do so, please check your configuration.")
-		} else {
-			s.logger.Infof("None of %d remote backup(s) were pruned.", lenCandidates)
-		}
-	}
-
-	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
-		candidates, err := filepath.Glob(
-			path.Join(s.c.BackupArchive, fmt.Sprintf("%s*", s.c.BackupPruningPrefix)),
-		)
-		if err != nil {
-			return fmt.Errorf(
-				"pruneOldBackups: error looking up matching files, starting with: %w", err,
-			)
-		}
-
-		var matches []string
-		for _, candidate := range candidates {
-			fi, err := os.Stat(candidate)
-			if err != nil {
-				return fmt.Errorf(
-					"pruneOldBackups: error calling stat on file %s: %w",
-					candidate,
-					err,
-				)
-			}
-
-			if fi.ModTime().Before(deadline) {
-				matches = append(matches, candidate)
-			}
-		}
-
-		if len(matches) != 0 && len(matches) != len(candidates) {
-			var removeErrors []error
-			for _, candidate := range matches {
-				if err := os.Remove(candidate); err != nil {
-					removeErrors = append(removeErrors, err)
-				}
-			}
-			if len(removeErrors) != 0 {
-				return fmt.Errorf(
-					"pruneOldBackups: %d error(s) deleting local files, starting with: %w",
-					len(removeErrors),
-					join(removeErrors...),
-				)
-			}
-			s.logger.Infof(
-				"Pruned %d out of %d local backup(s) as their age exceeded the configured retention period of %d days.",
-				len(matches),
-				len(candidates),
-				s.c.BackupRetentionDays,
-			)
-		} else if len(matches) != 0 && len(matches) == len(candidates) {
-			s.logger.Warnf(
-				"The current configuration would delete all %d local backup copies.",
-				len(matches),
-			)
-			s.logger.Warn("Refusing to do so, please check your configuration.")
-		} else {
-			s.logger.Infof("None of %d local backup(s) were pruned.", len(candidates))
-		}
-	}
-	return nil
-}
-
-// runHooks runs all hooks that have been registered using the
-// given level. In case executing a hook returns an error, the following
-// hooks will still be run before the function returns an error.
-func (s *script) runHooks(err error, targetLevel string) error {
-	var actionErrors []error
-	for _, hook := range s.hooks {
-		if hook.level != targetLevel {
-			continue
-		}
-		if err := hook.action(err, s.start, s.output.String()); err != nil {
-			actionErrors = append(actionErrors, err)
-		}
-	}
-	if len(actionErrors) != 0 {
-		return join(actionErrors...)
-	}
-	return nil
-}
-
-// must exits the script run prematurely in case the given error
-// is non-nil. If failure hooks have been registered on the script object, they
-// will be called, passing the failure and previous log output.
-func (s *script) must(err error) {
-	if err != nil {
-		s.logger.Errorf("Fatal error running backup: %s", err)
-		if hookErr := s.runHooks(err, hookLevelFailure); hookErr != nil {
-			s.logger.Errorf("An error occurred calling the registered failure hooks: %s", hookErr)
-		}
-		panic(errors.New(msgBackupFailed))
-	}
-}
-
-// lock opens a lockfile at the given location, keeping it locked until the
-// caller invokes the returned release func. When invoked while the file is
-// still locked the function panics.
-func lock(lockfile string) func() error {
-	fileLock := flock.New(lockfile)
-	acquired, err := fileLock.TryLock()
-	if err != nil {
-		panic(err)
-	}
-	if !acquired {
-		panic("unable to acquire file lock")
-	}
-	return fileLock.Unlock
-}
-
-// copy creates a copy of the file located at `dst` at `src`.
-func copy(src, dst string) error {
-	in, err := os.Open(src)
-	if err != nil {
-		return err
-	}
-	defer in.Close()
-
-	out, err := os.Create(dst)
-	if err != nil {
-		return err
-	}
-
-	_, err = io.Copy(out, in)
-	if err != nil {
-		out.Close()
-		return err
-	}
-	return out.Close()
-}
-
-// join takes a list of errors and joins them into a single error
-func join(errs ...error) error {
-	if len(errs) == 1 {
-		return errs[0]
-	}
-	var msgs []string
-	for _, err := range errs {
-		if err == nil {
-			continue
-		}
-		msgs = append(msgs, err.Error())
-	}
-	return errors.New("[" + strings.Join(msgs, ", ") + "]")
-}
-
-// buffer takes an io.Writer and returns a wrapped version of the
-// writer that writes to both the original target as well as the returned buffer
-func buffer(w io.Writer) (io.Writer, *bytes.Buffer) {
-	buffering := &bufferingWriter{buf: bytes.Buffer{}, writer: w}
-	return buffering, &buffering.buf
-}
-
-type bufferingWriter struct {
-	buf    bytes.Buffer
-	writer io.Writer
-}
-
-func (b *bufferingWriter) Write(p []byte) (n int, err error) {
-	if n, err := b.buf.Write(p); err != nil {
-		return n, fmt.Errorf("bufferingWriter: error writing to buffer: %w", err)
-	}
-	return b.writer.Write(p)
-}
-
-// hook contains a queued action that can be trigger them when the script
-// reaches a certain point (e.g. unsuccessful backup)
-type hook struct {
-	level  string
-	action func(err error, start time.Time, logOutput string) error
-}
-
-const (
-	hookLevelFailure = "failure"
-)

cmd/backup/notifications.go

@@ -0,0 +1,108 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"os"
+	"text/template"
+	"time"
+
+	sTypes "github.com/containrrr/shoutrrr/pkg/types"
+	"github.com/offen/docker-volume-backup/internal/utilities"
+)
+
+//go:embed notifications.tmpl
+var defaultNotifications string
+
+// NotificationData data to be passed to the notification templates
+type NotificationData struct {
+	Error  error
+	Config *Config
+	Stats  *Stats
+}
+
+// notify sends a notification using the given title and body templates.
+// Automatically creates notification data, adding the given error
+func (s *script) notify(titleTemplate string, bodyTemplate string, err error) error {
+	params := NotificationData{
+		Error:  err,
+		Stats:  s.stats,
+		Config: s.c,
+	}
+
+	titleBuf := &bytes.Buffer{}
+	if err := s.template.ExecuteTemplate(titleBuf, titleTemplate, params); err != nil {
+		return fmt.Errorf("notify: error executing %s template: %w", titleTemplate, err)
+	}
+
+	bodyBuf := &bytes.Buffer{}
+	if err := s.template.ExecuteTemplate(bodyBuf, bodyTemplate, params); err != nil {
+		return fmt.Errorf("notify: error executing %s template: %w", bodyTemplate, err)
+	}
+
+	if err := s.sendNotification(titleBuf.String(), bodyBuf.String()); err != nil {
+		return fmt.Errorf("notify: error notifying: %w", err)
+	}
+	return nil
+}
+
+// notifyFailure sends a notification about a failed backup run
+func (s *script) notifyFailure(err error) error {
+	return s.notify("title_failure", "body_failure", err)
+}
+
+// notifyFailure sends a notification about a successful backup run
+func (s *script) notifySuccess() error {
+	return s.notify("title_success", "body_success", nil)
+}
+
+// sendNotification sends a notification to all configured third party services
+func (s *script) sendNotification(title, body string) error {
+	var errs []error
+	for _, result := range s.sender.Send(body, &sTypes.Params{"title": title}) {
+		if result != nil {
+			errs = append(errs, result)
+		}
+	}
+	if len(errs) != 0 {
+		return fmt.Errorf("sendNotification: error sending message: %w", utilities.Join(errs...))
+	}
+	return nil
+}
+
+var templateHelpers = template.FuncMap{
+	"formatTime": func(t time.Time) string {
+		return t.Format(time.RFC3339)
+	},
+	"formatBytesDec": func(bytes uint64) string {
+		return formatBytes(bytes, true)
+	},
+	"formatBytesBin": func(bytes uint64) string {
+		return formatBytes(bytes, false)
+	},
+	"env": os.Getenv,
+}
+
+// formatBytes converts an amount of bytes in a human-readable representation
+// the decimal parameter specifies if using powers of 1000 (decimal) or powers of 1024 (binary)
+func formatBytes(b uint64, decimal bool) string {
+	unit := uint64(1024)
+	format := "%.1f %ciB"
+	if decimal {
+		unit = uint64(1000)
+		format = "%.1f %cB"
+	}
+	if b < unit {
+		return fmt.Sprintf("%d B", b)
+	}
+	div, exp := unit, 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf(format, float64(b)/float64(div), "kMGTPE"[exp])
+}

cmd/backup/notifications.tmpl

@@ -0,0 +1,26 @@
+{{ define "title_failure" -}}
+Failure running docker-volume-backup at {{ .Stats.StartTime | formatTime }}
+{{- end }}
+
+
+{{ define "body_failure" -}}
+Running docker-volume-backup failed with error: {{ .Error }}
+
+Log output of the failed run was:
+
+{{ .Stats.LogOutput }}
+{{- end }}
+
+
+{{ define "title_success" -}}
+Success running docker-volume-backup at {{ .Stats.StartTime | formatTime }}
+{{- end }}
+
+
+{{ define "body_success" -}}
+Running docker-volume-backup succeeded.
+
+Log output was:
+
+{{ .Stats.LogOutput }}
+{{- end }}

cmd/backup/script.go

@@ -0,0 +1,561 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"text/template"
+	"time"
+
+	"github.com/offen/docker-volume-backup/internal/storage"
+	"github.com/offen/docker-volume-backup/internal/storage/local"
+	"github.com/offen/docker-volume-backup/internal/storage/s3"
+	"github.com/offen/docker-volume-backup/internal/storage/ssh"
+	"github.com/offen/docker-volume-backup/internal/storage/webdav"
+	"github.com/offen/docker-volume-backup/internal/utilities"
+
+	"github.com/containrrr/shoutrrr"
+	"github.com/containrrr/shoutrrr/pkg/router"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/filters"
+	"github.com/docker/docker/api/types/swarm"
+	"github.com/docker/docker/client"
+	"github.com/kelseyhightower/envconfig"
+	"github.com/leekchan/timeutil"
+	"github.com/otiai10/copy"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/crypto/openpgp"
+	"golang.org/x/sync/errgroup"
+)
+
+// script holds all the stateful information required to orchestrate a
+// single backup run.
+type script struct {
+	cli       *client.Client
+	storages  []storage.Backend
+	logger    *logrus.Logger
+	sender    *router.ServiceRouter
+	template  *template.Template
+	hooks     []hook
+	hookLevel hookLevel
+
+	file  string
+	stats *Stats
+
+	encounteredLock bool
+
+	c *Config
+}
+
+// newScript creates all resources needed for the script to perform actions against
+// remote resources like the Docker engine or remote storage locations. All
+// reading from env vars or other configuration sources is expected to happen
+// in this method.
+func newScript() (*script, error) {
+	stdOut, logBuffer := buffer(os.Stdout)
+	s := &script{
+		c: &Config{},
+		logger: &logrus.Logger{
+			Out:       stdOut,
+			Formatter: new(logrus.TextFormatter),
+			Hooks:     make(logrus.LevelHooks),
+			Level:     logrus.InfoLevel,
+		},
+		stats: &Stats{
+			StartTime: time.Now(),
+			LogOutput: logBuffer,
+			Storages: map[string]StorageStats{
+				"S3":     {},
+				"WebDAV": {},
+				"SSH":    {},
+				"Local":  {},
+			},
+		},
+	}
+
+	s.registerHook(hookLevelPlumbing, func(error) error {
+		s.stats.EndTime = time.Now()
+		s.stats.TookTime = s.stats.EndTime.Sub(s.stats.StartTime)
+		return nil
+	})
+
+	if err := envconfig.Process("", s.c); err != nil {
+		return nil, fmt.Errorf("newScript: failed to process configuration values: %w", err)
+	}
+
+	s.file = path.Join("/tmp", s.c.BackupFilename)
+	if s.c.BackupFilenameExpand {
+		s.file = os.ExpandEnv(s.file)
+		s.c.BackupLatestSymlink = os.ExpandEnv(s.c.BackupLatestSymlink)
+		s.c.BackupPruningPrefix = os.ExpandEnv(s.c.BackupPruningPrefix)
+	}
+	s.file = timeutil.Strftime(&s.stats.StartTime, s.file)
+
+	_, err := os.Stat("/var/run/docker.sock")
+	_, dockerHostSet := os.LookupEnv("DOCKER_HOST")
+	if !os.IsNotExist(err) || dockerHostSet {
+		cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
+		if err != nil {
+			return nil, fmt.Errorf("newScript: failed to create docker client")
+		}
+		s.cli = cli
+	}
+
+	logFunc := func(logType storage.LogLevel, context string, msg string, params ...interface{}) {
+		switch logType {
+		case storage.LogLevelWarning:
+			s.logger.Warnf("["+context+"] "+msg, params...)
+		case storage.LogLevelError:
+			s.logger.Errorf("["+context+"] "+msg, params...)
+		case storage.LogLevelInfo:
+		default:
+			s.logger.Infof("["+context+"] "+msg, params...)
+		}
+	}
+
+	if s.c.AwsS3BucketName != "" {
+		accessKeyID, err := s.c.resolveSecret(s.c.AwsAccessKeyID, s.c.AwsAccessKeyIDFile)
+		if err != nil {
+			return nil, fmt.Errorf("newScript: error resolving AwsAccessKeyID: %w", err)
+		}
+		secretAccessKey, err := s.c.resolveSecret(s.c.AwsSecretAccessKey, s.c.AwsSecretAccessKeyFile)
+		if err != nil {
+			return nil, fmt.Errorf("newScript: error resolving AwsSecretAccessKey: %w", err)
+		}
+		s3Config := s3.Config{
+			Endpoint:         s.c.AwsEndpoint,
+			AccessKeyID:      accessKeyID,
+			SecretAccessKey:  secretAccessKey,
+			IamRoleEndpoint:  s.c.AwsIamRoleEndpoint,
+			EndpointProto:    s.c.AwsEndpointProto,
+			EndpointInsecure: s.c.AwsEndpointInsecure,
+			RemotePath:       s.c.AwsS3Path,
+			BucketName:       s.c.AwsS3BucketName,
+			StorageClass:     s.c.AwsStorageClass,
+		}
+		if s3Backend, err := s3.NewStorageBackend(s3Config, logFunc); err != nil {
+			return nil, err
+		} else {
+			s.storages = append(s.storages, s3Backend)
+		}
+	}
+
+	if s.c.WebdavUrl != "" {
+		webDavConfig := webdav.Config{
+			URL:         s.c.WebdavUrl,
+			URLInsecure: s.c.WebdavUrlInsecure,
+			Username:    s.c.WebdavUsername,
+			Password:    s.c.WebdavPassword,
+			RemotePath:  s.c.WebdavPath,
+		}
+		if webdavBackend, err := webdav.NewStorageBackend(webDavConfig, logFunc); err != nil {
+			return nil, err
+		} else {
+			s.storages = append(s.storages, webdavBackend)
+		}
+	}
+
+	if s.c.SSHHostName != "" {
+		sshConfig := ssh.Config{
+			HostName:           s.c.SSHHostName,
+			Port:               s.c.SSHPort,
+			User:               s.c.SSHUser,
+			Password:           s.c.SSHPassword,
+			IdentityFile:       s.c.SSHIdentityFile,
+			IdentityPassphrase: s.c.SSHIdentityPassphrase,
+			RemotePath:         s.c.SSHRemotePath,
+		}
+		if sshBackend, err := ssh.NewStorageBackend(sshConfig, logFunc); err != nil {
+			return nil, err
+		} else {
+			s.storages = append(s.storages, sshBackend)
+		}
+	}
+
+	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
+		localConfig := local.Config{
+			ArchivePath:   s.c.BackupArchive,
+			LatestSymlink: s.c.BackupLatestSymlink,
+		}
+		localBackend := local.NewStorageBackend(localConfig, logFunc)
+		s.storages = append(s.storages, localBackend)
+	}
+
+	if s.c.EmailNotificationRecipient != "" {
+		emailURL := fmt.Sprintf(
+			"smtp://%s:%s@%s:%d/?from=%s&to=%s",
+			s.c.EmailSMTPUsername,
+			s.c.EmailSMTPPassword,
+			s.c.EmailSMTPHost,
+			s.c.EmailSMTPPort,
+			s.c.EmailNotificationSender,
+			s.c.EmailNotificationRecipient,
+		)
+		s.c.NotificationURLs = append(s.c.NotificationURLs, emailURL)
+		s.logger.Warn(
+			"Using EMAIL_* keys for providing notification configuration has been deprecated and will be removed in the next major version.",
+		)
+		s.logger.Warn(
+			"Please use NOTIFICATION_URLS instead. Refer to the README for an upgrade guide.",
+		)
+	}
+
+	hookLevel, ok := hookLevels[s.c.NotificationLevel]
+	if !ok {
+		return nil, fmt.Errorf("newScript: unknown NOTIFICATION_LEVEL %s", s.c.NotificationLevel)
+	}
+	s.hookLevel = hookLevel
+
+	if len(s.c.NotificationURLs) > 0 {
+		sender, senderErr := shoutrrr.CreateSender(s.c.NotificationURLs...)
+		if senderErr != nil {
+			return nil, fmt.Errorf("newScript: error creating sender: %w", senderErr)
+		}
+		s.sender = sender
+
+		tmpl := template.New("")
+		tmpl.Funcs(templateHelpers)
+		tmpl, err = tmpl.Parse(defaultNotifications)
+		if err != nil {
+			return nil, fmt.Errorf("newScript: unable to parse default notifications templates: %w", err)
+		}
+
+		if fi, err := os.Stat("/etc/dockervolumebackup/notifications.d"); err == nil && fi.IsDir() {
+			tmpl, err = tmpl.ParseGlob("/etc/dockervolumebackup/notifications.d/*.*")
+			if err != nil {
+				return nil, fmt.Errorf("newScript: unable to parse user defined notifications templates: %w", err)
+			}
+		}
+		s.template = tmpl
+
+		// To prevent duplicate notifications, ensure the regsistered callbacks
+		// run mutually exclusive.
+		s.registerHook(hookLevelError, func(err error) error {
+			if err == nil {
+				return nil
+			}
+			return s.notifyFailure(err)
+		})
+		s.registerHook(hookLevelInfo, func(err error) error {
+			if err != nil {
+				return nil
+			}
+			return s.notifySuccess()
+		})
+	}
+
+	return s, nil
+}
+
+// stopContainers stops all Docker containers that are marked as to being
+// stopped during the backup and returns a function that can be called to
+// restart everything that has been stopped.
+func (s *script) stopContainers() (func() error, error) {
+	if s.cli == nil {
+		return noop, nil
+	}
+
+	allContainers, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+		Quiet: true,
+	})
+	if err != nil {
+		return noop, fmt.Errorf("stopContainers: error querying for containers: %w", err)
+	}
+
+	containerLabel := fmt.Sprintf(
+		"docker-volume-backup.stop-during-backup=%s",
+		s.c.BackupStopContainerLabel,
+	)
+	containersToStop, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+		Quiet: true,
+		Filters: filters.NewArgs(filters.KeyValuePair{
+			Key:   "label",
+			Value: containerLabel,
+		}),
+	})
+
+	if err != nil {
+		return noop, fmt.Errorf("stopContainers: error querying for containers to stop: %w", err)
+	}
+
+	if len(containersToStop) == 0 {
+		return noop, nil
+	}
+
+	s.logger.Infof(
+		"Stopping %d container(s) labeled `%s` out of %d running container(s).",
+		len(containersToStop),
+		containerLabel,
+		len(allContainers),
+	)
+
+	var stoppedContainers []types.Container
+	var stopErrors []error
+	for _, container := range containersToStop {
+		if err := s.cli.ContainerStop(context.Background(), container.ID, nil); err != nil {
+			stopErrors = append(stopErrors, err)
+		} else {
+			stoppedContainers = append(stoppedContainers, container)
+		}
+	}
+
+	var stopError error
+	if len(stopErrors) != 0 {
+		stopError = fmt.Errorf(
+			"stopContainers: %d error(s) stopping containers: %w",
+			len(stopErrors),
+			utilities.Join(stopErrors...),
+		)
+	}
+
+	s.stats.Containers = ContainersStats{
+		All:     uint(len(allContainers)),
+		ToStop:  uint(len(containersToStop)),
+		Stopped: uint(len(stoppedContainers)),
+	}
+
+	return func() error {
+		servicesRequiringUpdate := map[string]struct{}{}
+
+		var restartErrors []error
+		for _, container := range stoppedContainers {
+			if swarmServiceName, ok := container.Labels["com.docker.swarm.service.name"]; ok {
+				servicesRequiringUpdate[swarmServiceName] = struct{}{}
+				continue
+			}
+			if err := s.cli.ContainerStart(context.Background(), container.ID, types.ContainerStartOptions{}); err != nil {
+				restartErrors = append(restartErrors, err)
+			}
+		}
+
+		if len(servicesRequiringUpdate) != 0 {
+			services, _ := s.cli.ServiceList(context.Background(), types.ServiceListOptions{})
+			for serviceName := range servicesRequiringUpdate {
+				var serviceMatch swarm.Service
+				for _, service := range services {
+					if service.Spec.Name == serviceName {
+						serviceMatch = service
+						break
+					}
+				}
+				if serviceMatch.ID == "" {
+					return fmt.Errorf("stopContainers: couldn't find service with name %s", serviceName)
+				}
+				serviceMatch.Spec.TaskTemplate.ForceUpdate = 1
+				if _, err := s.cli.ServiceUpdate(
+					context.Background(), serviceMatch.ID,
+					serviceMatch.Version, serviceMatch.Spec, types.ServiceUpdateOptions{},
+				); err != nil {
+					restartErrors = append(restartErrors, err)
+				}
+			}
+		}
+
+		if len(restartErrors) != 0 {
+			return fmt.Errorf(
+				"stopContainers: %d error(s) restarting containers and services: %w",
+				len(restartErrors),
+				utilities.Join(restartErrors...),
+			)
+		}
+		s.logger.Infof(
+			"Restarted %d container(s) and the matching service(s).",
+			len(stoppedContainers),
+		)
+		return nil
+	}, stopError
+}
+
+// createArchive creates a tar archive of the configured backup location and
+// saves it to disk.
+func (s *script) createArchive() error {
+	backupSources := s.c.BackupSources
+
+	if s.c.BackupFromSnapshot {
+		s.logger.Warn(
+			"Using BACKUP_FROM_SNAPSHOT has been deprecated and will be removed in the next major version.",
+		)
+		s.logger.Warn(
+			"Please use `archive-pre` and `archive-post` commands to prepare your backup sources. Refer to the README for an upgrade guide.",
+		)
+		backupSources = filepath.Join("/tmp", s.c.BackupSources)
+		// copy before compressing guard against a situation where backup folder's content are still growing.
+		s.registerHook(hookLevelPlumbing, func(error) error {
+			if err := remove(backupSources); err != nil {
+				return fmt.Errorf("createArchive: error removing snapshot: %w", err)
+			}
+			s.logger.Infof("Removed snapshot `%s`.", backupSources)
+			return nil
+		})
+		if err := copy.Copy(s.c.BackupSources, backupSources, copy.Options{
+			PreserveTimes: true,
+			PreserveOwner: true,
+		}); err != nil {
+			return fmt.Errorf("createArchive: error creating snapshot: %w", err)
+		}
+		s.logger.Infof("Created snapshot of `%s` at `%s`.", s.c.BackupSources, backupSources)
+	}
+
+	tarFile := s.file
+	s.registerHook(hookLevelPlumbing, func(error) error {
+		if err := remove(tarFile); err != nil {
+			return fmt.Errorf("createArchive: error removing tar file: %w", err)
+		}
+		s.logger.Infof("Removed tar file `%s`.", tarFile)
+		return nil
+	})
+
+	backupPath, err := filepath.Abs(stripTrailingSlashes(backupSources))
+	if err != nil {
+		return fmt.Errorf("createArchive: error getting absolute path: %w", err)
+	}
+
+	var filesEligibleForBackup []string
+	if err := filepath.WalkDir(backupPath, func(path string, di fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if s.c.BackupExcludeRegexp.Re != nil && s.c.BackupExcludeRegexp.Re.MatchString(path) {
+			return nil
+		}
+		filesEligibleForBackup = append(filesEligibleForBackup, path)
+		return nil
+	}); err != nil {
+		return fmt.Errorf("createArchive: error walking filesystem tree: %w", err)
+	}
+
+	if err := createArchive(filesEligibleForBackup, backupSources, tarFile); err != nil {
+		return fmt.Errorf("createArchive: error compressing backup folder: %w", err)
+	}
+
+	s.logger.Infof("Created backup of `%s` at `%s`.", backupSources, tarFile)
+	return nil
+}
+
+// encryptArchive encrypts the backup file using PGP and the configured passphrase.
+// In case no passphrase is given it returns early, leaving the backup file
+// untouched.
+func (s *script) encryptArchive() error {
+	if s.c.GpgPassphrase == "" {
+		return nil
+	}
+
+	gpgFile := fmt.Sprintf("%s.gpg", s.file)
+	s.registerHook(hookLevelPlumbing, func(error) error {
+		if err := remove(gpgFile); err != nil {
+			return fmt.Errorf("encryptArchive: error removing gpg file: %w", err)
+		}
+		s.logger.Infof("Removed GPG file `%s`.", gpgFile)
+		return nil
+	})
+
+	outFile, err := os.Create(gpgFile)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error opening out file: %w", err)
+	}
+	defer outFile.Close()
+
+	_, name := path.Split(s.file)
+	dst, err := openpgp.SymmetricallyEncrypt(outFile, []byte(s.c.GpgPassphrase), &openpgp.FileHints{
+		IsBinary: true,
+		FileName: name,
+	}, nil)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error encrypting backup file: %w", err)
+	}
+	defer dst.Close()
+
+	src, err := os.Open(s.file)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error opening backup file `%s`: %w", s.file, err)
+	}
+
+	if _, err := io.Copy(dst, src); err != nil {
+		return fmt.Errorf("encryptArchive: error writing ciphertext to file: %w", err)
+	}
+
+	s.file = gpgFile
+	s.logger.Infof("Encrypted backup using given passphrase, saving as `%s`.", s.file)
+	return nil
+}
+
+// copyArchive makes sure the backup file is copied to both local and remote locations
+// as per the given configuration.
+func (s *script) copyArchive() error {
+	_, name := path.Split(s.file)
+	if stat, err := os.Stat(s.file); err != nil {
+		return fmt.Errorf("copyArchive: unable to stat backup file: %w", err)
+	} else {
+		size := stat.Size()
+		s.stats.BackupFile = BackupFileStats{
+			Size:     uint64(size),
+			Name:     name,
+			FullPath: s.file,
+		}
+	}
+
+	eg := errgroup.Group{}
+	for _, backend := range s.storages {
+		b := backend
+		eg.Go(func() error {
+			return b.Copy(s.file)
+		})
+	}
+	if err := eg.Wait(); err != nil {
+		return fmt.Errorf("copyArchive: error copying archive: %w", err)
+	}
+
+	return nil
+}
+
+// pruneBackups rotates away backups from local and remote storages using
+// the given configuration. In case the given configuration would delete all
+// backups, it does nothing instead and logs a warning.
+func (s *script) pruneBackups() error {
+	if s.c.BackupRetentionDays < 0 {
+		return nil
+	}
+
+	deadline := time.Now().AddDate(0, 0, -int(s.c.BackupRetentionDays)).Add(s.c.BackupPruningLeeway)
+
+	eg := errgroup.Group{}
+	for _, backend := range s.storages {
+		b := backend
+		eg.Go(func() error {
+			stats, err := b.Prune(deadline, s.c.BackupPruningPrefix)
+			if err != nil {
+				return err
+			}
+			s.stats.Lock()
+			s.stats.Storages[b.Name()] = StorageStats{
+				Total:  stats.Total,
+				Pruned: stats.Pruned,
+			}
+			s.stats.Unlock()
+			return nil
+		})
+	}
+
+	if err := eg.Wait(); err != nil {
+		return fmt.Errorf("pruneBackups: error pruning backups: %w", err)
+	}
+
+	return nil
+}
+
+// must exits the script run prematurely in case the given error
+// is non-nil.
+func (s *script) must(err error) {
+	if err != nil {
+		s.logger.Errorf("Fatal error running backup: %s", err)
+		panic(err)
+	}
+}

cmd/backup/stats.go

@@ -0,0 +1,45 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	"sync"
+	"time"
+)
+
+// ContainersStats stats about the docker containers
+type ContainersStats struct {
+	All        uint
+	ToStop     uint
+	Stopped    uint
+	StopErrors uint
+}
+
+// BackupFileStats stats about the created backup file
+type BackupFileStats struct {
+	Name     string
+	FullPath string
+	Size     uint64
+}
+
+// StorageStats stats about the status of an archival directory
+type StorageStats struct {
+	Total       uint
+	Pruned      uint
+	PruneErrors uint
+}
+
+// Stats global stats regarding script execution
+type Stats struct {
+	sync.Mutex
+	StartTime  time.Time
+	EndTime    time.Time
+	TookTime   time.Duration
+	LockedTime time.Duration
+	LogOutput  *bytes.Buffer
+	Containers ContainersStats
+	BackupFile BackupFileStats
+	Storages   map[string]StorageStats
+}

cmd/backup/util.go

@@ -0,0 +1,52 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+)
+
+var noop = func() error { return nil }
+
+// remove removes the given file or directory from disk.
+func remove(location string) error {
+	fi, err := os.Lstat(location)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("remove: error checking for existence of `%s`: %w", location, err)
+	}
+	if fi.IsDir() {
+		err = os.RemoveAll(location)
+	} else {
+		err = os.Remove(location)
+	}
+	if err != nil {
+		return fmt.Errorf("remove: error removing `%s`: %w", location, err)
+	}
+	return nil
+}
+
+// buffer takes an io.Writer and returns a wrapped version of the
+// writer that writes to both the original target as well as the returned buffer
+func buffer(w io.Writer) (io.Writer, *bytes.Buffer) {
+	buffering := &bufferingWriter{buf: bytes.Buffer{}, writer: w}
+	return buffering, &buffering.buf
+}
+
+type bufferingWriter struct {
+	buf    bytes.Buffer
+	writer io.Writer
+}
+
+func (b *bufferingWriter) Write(p []byte) (n int, err error) {
+	if n, err := b.buf.Write(p); err != nil {
+		return n, fmt.Errorf("(*bufferingWriter).Write: error writing to buffer: %w", err)
+	}
+	return b.writer.Write(p)
+}

docs/NOTIFICATION-TEMPLATES.md

@@ -0,0 +1,40 @@
+# Notification templates reference
+
+In order to customize title and body of notifications you'll have to write a [go template](https://pkg.go.dev/text/template) and mount it inside the `/etc/dockervolumebackup/notifications.d/` directory.
+
+Configuration, data about the backup run and helper functions will be passed to this template, this page documents them fully.
+
+## Data
+Here is a list of all data passed to the template:
+
+* `Config`: this object holds the configuration that has been passed to the script. The field names are the name of the recognized environment variables converted in PascalCase. (e.g. `BACKUP_STOP_CONTAINER_LABEL` becomes `BackupStopContainerLabel`)
+* `Error`: the error that made the backup fail. Only available in the `title_failure` and `body_failure` templates
+* `Stats`: objects that holds stats regarding script execution. In case of an unsuccessful run, some information may not be available.
+  * `StartTime`: time when the script started execution
+  * `EndTime`: time when the backup has completed successfully (after pruning)
+  * `TookTime`: amount of time it took for the backup to run. (equal to `EndTime - StartTime`)
+  * `LockedTime`: amount of time it took for the backup to acquire the exclusive lock
+  * `LogOutput`: full log of the application
+  * `Containers`: object containing stats about the docker containers
+    * `All`: total number of containers
+    * `ToStop`: number of containers matched by the stop rule
+    * `Stopped`: number of containers successfully stopped
+    * `StopErrors`: number of containers that were unable to be stopped (equal to `ToStop - Stopped`)
+  * `BackupFile`: object containing information about the backup file
+    * `Name`: name of the backup file (e.g. `backup-2022-02-11T01-00-00.tar.gz`)
+    * `FullPath`: full path of the backup file (e.g. `/archive/backup-2022-02-11T01-00-00.tar.gz`)
+    * `Size`: size in bytes of the backup file
+  * `Storages`: object that holds stats about each storage
+    * `Local`, `S3`, `WebDAV` or `SSH`:
+      * `Total`: total number of backup files
+      * `Pruned`: number of backup files that were deleted due to pruning rule
+      * `PruneErrors`: number of backup files that were unable to be pruned
+
+## Functions
+
+Some formatting and helper functions are also available:
+
+* `formatTime`: formats a time object using [RFC3339](https://datatracker.ietf.org/doc/html/rfc3339) format (e.g. `2022-02-11T01:00:00Z`)
+* `formatBytesBin`: formats an amount of bytes using powers of 1024 (e.g. `7055258` bytes will be `6.7 MiB`) 
+* `formatBytesDec`: formats an amount of bytes using powers of 1000 (e.g. `7055258` bytes will be `7.1 MB`)
+* `env`: returns the value of the environment variable of the given key if set

entrypoint.sh

@@ -5,10 +5,22 @@
 
 set -e
 
-BACKUP_CRON_EXPRESSION="${BACKUP_CRON_EXPRESSION:-@daily}"
+if [ ! -d "/etc/dockervolumebackup/conf.d" ]; then
+  BACKUP_CRON_EXPRESSION="${BACKUP_CRON_EXPRESSION:-@daily}"
 
-echo "Installing cron.d entry with expression $BACKUP_CRON_EXPRESSION."
-echo "$BACKUP_CRON_EXPRESSION backup 2>&1" | crontab -
+  echo "Installing cron.d entry with expression $BACKUP_CRON_EXPRESSION."
+  echo "$BACKUP_CRON_EXPRESSION backup 2>&1" | crontab -
+else
+  echo "/etc/dockervolumebackup/conf.d was found, using configuration files from this directory."
+
+  crontab -r && crontab /dev/null
+  for file in /etc/dockervolumebackup/conf.d/*; do
+    source $file
+    BACKUP_CRON_EXPRESSION="${BACKUP_CRON_EXPRESSION:-@daily}"
+    echo "Appending cron.d entry with expression $BACKUP_CRON_EXPRESSION and configuration file $file"
+    (crontab -l; echo "$BACKUP_CRON_EXPRESSION /bin/sh -c 'set -a; source $file; set +a && backup' 2>&1") | crontab -
+  done
+fi
 
 echo "Starting cron in foreground."
-crond -f -l 8
+crond -f -d 8

go.mod

@@ -1,47 +1,67 @@
 module github.com/offen/docker-volume-backup
 
-go 1.17
+go 1.19
 
 require (
-	github.com/docker/docker v20.10.8+incompatible
+	github.com/containrrr/shoutrrr v0.5.2
+	github.com/cosiner/argv v0.1.0
+	github.com/docker/docker v20.10.11+incompatible
 	github.com/gofrs/flock v0.8.1
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d
-	github.com/m90/targz v0.0.0-20210904082215-2e9a4529a615
-	github.com/minio/minio-go/v7 v7.0.12
+	github.com/minio/minio-go/v7 v7.0.16
+	github.com/otiai10/copy v1.7.0
+	github.com/pkg/sftp v1.13.5
 	github.com/sirupsen/logrus v1.8.1
-	golang.org/x/crypto v0.0.0-20210817164053-32db794688a5
+	github.com/studio-b12/gowebdav v0.0.0-20220128162035-c7b1ff8a5e62
+	golang.org/x/crypto v0.0.0-20211215153901-e495a2d5b3d3
+	golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f
 )
 
 require (
-	github.com/Microsoft/go-winio v0.4.17 // indirect
-	github.com/containerd/containerd v1.5.5 // indirect
+	github.com/Microsoft/go-winio v0.5.2 // indirect
+	github.com/containerd/containerd v1.6.6 // indirect
 	github.com/docker/distribution v2.7.1+incompatible // indirect
 	github.com/docker/go-connections v0.4.0 // indirect
 	github.com/docker/go-units v0.4.0 // indirect
 	github.com/dustin/go-humanize v1.0.0 // indirect
-	github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df // indirect
+	github.com/fatih/color v1.10.0 // indirect
+	github.com/fsnotify/fsnotify v1.4.9 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
-	github.com/golang/protobuf v1.5.0 // indirect
-	github.com/google/uuid v1.2.0 // indirect
-	github.com/json-iterator/go v1.1.10 // indirect
-	github.com/klauspost/cpuid v1.3.1 // indirect
-	github.com/minio/md5-simd v1.1.0 // indirect
-	github.com/minio/sha256-simd v0.1.1 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/google/uuid v1.3.0 // indirect
+	github.com/gorilla/mux v1.7.3 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.15.6 // indirect
+	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
+	github.com/kr/fs v0.1.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/mattn/go-colorable v0.1.8 // indirect
+	github.com/mattn/go-isatty v0.0.12 // indirect
+	github.com/minio/md5-simd v1.1.2 // indirect
+	github.com/minio/sha256-simd v1.0.0 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
+	github.com/moby/term v0.0.0-20200312100748-672ec06f55cd // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
-	github.com/modern-go/reflect2 v1.0.1 // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/morikuni/aec v1.0.0 // indirect
+	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
+	github.com/nxadm/tail v1.4.6 // indirect
+	github.com/onsi/ginkgo v1.14.2 // indirect
+	github.com/onsi/gomega v1.10.3 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
-	github.com/opencontainers/image-spec v1.0.1 // indirect
+	github.com/opencontainers/image-spec v1.0.3-0.20211202183452-c5a74bcca799 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
-	github.com/rs/xid v1.2.1 // indirect
-	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 // indirect
-	golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 // indirect
-	golang.org/x/text v0.3.4 // indirect
-	google.golang.org/genproto v0.0.0-20201110150050-8816d57aaa9a // indirect
-	google.golang.org/grpc v1.33.2 // indirect
-	google.golang.org/protobuf v1.26.0 // indirect
-	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
-	gopkg.in/ini.v1 v1.57.0 // indirect
+	github.com/rs/xid v1.3.0 // indirect
+	golang.org/x/net v0.0.0-20220607020251-c690dde0001d // indirect
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+	golang.org/x/text v0.3.7 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	google.golang.org/genproto v0.0.0-20220602131408-e326c6e8e9c8 // indirect
+	google.golang.org/grpc v1.47.0 // indirect
+	google.golang.org/protobuf v1.28.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
+	gopkg.in/ini.v1 v1.65.0 // indirect
+	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 )

internal/storage/local/local.go

@@ -0,0 +1,160 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package local
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"time"
+
+	"github.com/offen/docker-volume-backup/internal/storage"
+	"github.com/offen/docker-volume-backup/internal/utilities"
+)
+
+type localStorage struct {
+	*storage.StorageBackend
+	latestSymlink string
+}
+
+// Config allows configuration of a local storage backend.
+type Config struct {
+	ArchivePath   string
+	LatestSymlink string
+}
+
+// NewStorageBackend creates and initializes a new local storage backend.
+func NewStorageBackend(opts Config, logFunc storage.Log) storage.Backend {
+	return &localStorage{
+		StorageBackend: &storage.StorageBackend{
+			DestinationPath: opts.ArchivePath,
+			Log:             logFunc,
+		},
+		latestSymlink: opts.LatestSymlink,
+	}
+}
+
+// Name return the name of the storage backend
+func (b *localStorage) Name() string {
+	return "Local"
+}
+
+// Copy copies the given file to the local storage backend.
+func (b *localStorage) Copy(file string) error {
+	_, name := path.Split(file)
+
+	if err := copyFile(file, path.Join(b.DestinationPath, name)); err != nil {
+		return fmt.Errorf("(*localStorage).Copy: Error copying file to local archive: %w", err)
+	}
+	b.Log(storage.LogLevelInfo, b.Name(), "Stored copy of backup `%s` in local archive `%s`.", file, b.DestinationPath)
+
+	if b.latestSymlink != "" {
+		symlink := path.Join(b.DestinationPath, b.latestSymlink)
+		if _, err := os.Lstat(symlink); err == nil {
+			os.Remove(symlink)
+		}
+		if err := os.Symlink(name, symlink); err != nil {
+			return fmt.Errorf("(*localStorage).Copy: error creating latest symlink: %w", err)
+		}
+		b.Log(storage.LogLevelInfo, b.Name(), "Created/Updated symlink `%s` for latest backup.", b.latestSymlink)
+	}
+
+	return nil
+}
+
+// Prune rotates away backups according to the configuration and provided deadline for the local storage backend.
+func (b *localStorage) Prune(deadline time.Time, pruningPrefix string) (*storage.PruneStats, error) {
+	globPattern := path.Join(
+		b.DestinationPath,
+		fmt.Sprintf("%s*", pruningPrefix),
+	)
+	globMatches, err := filepath.Glob(globPattern)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"(*localStorage).Prune: Error looking up matching files using pattern %s: %w",
+			globPattern,
+			err,
+		)
+	}
+
+	var candidates []string
+	for _, candidate := range globMatches {
+		fi, err := os.Lstat(candidate)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"(*localStorage).Prune: Error calling Lstat on file %s: %w",
+				candidate,
+				err,
+			)
+		}
+
+		if fi.Mode()&os.ModeSymlink != os.ModeSymlink {
+			candidates = append(candidates, candidate)
+		}
+	}
+
+	var matches []string
+	for _, candidate := range candidates {
+		fi, err := os.Stat(candidate)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"(*localStorage).Prune: Error calling stat on file %s: %w",
+				candidate,
+				err,
+			)
+		}
+		if fi.ModTime().Before(deadline) {
+			matches = append(matches, candidate)
+		}
+	}
+
+	stats := &storage.PruneStats{
+		Total:  uint(len(candidates)),
+		Pruned: uint(len(matches)),
+	}
+
+	if err := b.DoPrune(b.Name(), len(matches), len(candidates), "local backup(s)", func() error {
+		var removeErrors []error
+		for _, match := range matches {
+			if err := os.Remove(match); err != nil {
+				removeErrors = append(removeErrors, err)
+			}
+		}
+		if len(removeErrors) != 0 {
+			return fmt.Errorf(
+				"(*localStorage).Prune: %d error(s) deleting local files, starting with: %w",
+				len(removeErrors),
+				utilities.Join(removeErrors...),
+			)
+		}
+		return nil
+	}); err != nil {
+		return stats, err
+	}
+
+	return stats, nil
+}
+
+// copy creates a copy of the file located at `dst` at `src`.
+func copyFile(src, dst string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(out, in)
+	if err != nil {
+		out.Close()
+		return err
+	}
+	return out.Close()
+}

internal/storage/s3/s3.go

@@ -0,0 +1,163 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package s3
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"path"
+	"path/filepath"
+	"time"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+	"github.com/offen/docker-volume-backup/internal/storage"
+	"github.com/offen/docker-volume-backup/internal/utilities"
+)
+
+type s3Storage struct {
+	*storage.StorageBackend
+	client       *minio.Client
+	bucket       string
+	storageClass string
+}
+
+// Config contains values that define the configuration of a S3 backend.
+type Config struct {
+	Endpoint         string
+	AccessKeyID      string
+	SecretAccessKey  string
+	IamRoleEndpoint  string
+	EndpointProto    string
+	EndpointInsecure bool
+	RemotePath       string
+	BucketName       string
+	StorageClass     string
+}
+
+// NewStorageBackend creates and initializes a new S3/Minio storage backend.
+func NewStorageBackend(opts Config, logFunc storage.Log) (storage.Backend, error) {
+
+	var creds *credentials.Credentials
+	if opts.AccessKeyID != "" && opts.SecretAccessKey != "" {
+		creds = credentials.NewStaticV4(
+			opts.AccessKeyID,
+			opts.SecretAccessKey,
+			"",
+		)
+	} else if opts.IamRoleEndpoint != "" {
+		creds = credentials.NewIAM(opts.IamRoleEndpoint)
+	} else {
+		return nil, errors.New("NewStorageBackend: AWS_S3_BUCKET_NAME is defined, but no credentials were provided")
+	}
+
+	options := minio.Options{
+		Creds:  creds,
+		Secure: opts.EndpointProto == "https",
+	}
+
+	if opts.EndpointInsecure {
+		if !options.Secure {
+			return nil, errors.New("NewStorageBackend: AWS_ENDPOINT_INSECURE = true is only meaningful for https")
+		}
+
+		transport, err := minio.DefaultTransport(true)
+		if err != nil {
+			return nil, fmt.Errorf("NewStorageBackend: failed to create default minio transport: %w", err)
+		}
+		transport.TLSClientConfig.InsecureSkipVerify = true
+		options.Transport = transport
+	}
+
+	mc, err := minio.New(opts.Endpoint, &options)
+	if err != nil {
+		return nil, fmt.Errorf("NewStorageBackend: error setting up minio client: %w", err)
+	}
+
+	return &s3Storage{
+		StorageBackend: &storage.StorageBackend{
+			DestinationPath: opts.RemotePath,
+			Log:             logFunc,
+		},
+		client:       mc,
+		bucket:       opts.BucketName,
+		storageClass: opts.StorageClass,
+	}, nil
+}
+
+// Name returns the name of the storage backend
+func (v *s3Storage) Name() string {
+	return "S3"
+}
+
+// Copy copies the given file to the S3/Minio storage backend.
+func (b *s3Storage) Copy(file string) error {
+	_, name := path.Split(file)
+
+	if _, err := b.client.FPutObject(context.Background(), b.bucket, filepath.Join(b.DestinationPath, name), file, minio.PutObjectOptions{
+		ContentType:  "application/tar+gzip",
+		StorageClass: b.storageClass,
+	}); err != nil {
+		errResp := minio.ToErrorResponse(err)
+		return fmt.Errorf("(*s3Storage).Copy: error uploading backup to remote storage: [Message]: '%s', [Code]: %s, [StatusCode]: %d", errResp.Message, errResp.Code, errResp.StatusCode)
+	}
+	b.Log(storage.LogLevelInfo, b.Name(), "Uploaded a copy of backup `%s` to bucket `%s`.", file, b.bucket)
+
+	return nil
+}
+
+// Prune rotates away backups according to the configuration and provided deadline for the S3/Minio storage backend.
+func (b *s3Storage) Prune(deadline time.Time, pruningPrefix string) (*storage.PruneStats, error) {
+	candidates := b.client.ListObjects(context.Background(), b.bucket, minio.ListObjectsOptions{
+		WithMetadata: true,
+		Prefix:       filepath.Join(b.DestinationPath, pruningPrefix),
+		Recursive:    true,
+	})
+
+	var matches []minio.ObjectInfo
+	var lenCandidates int
+	for candidate := range candidates {
+		lenCandidates++
+		if candidate.Err != nil {
+			return nil, fmt.Errorf(
+				"(*s3Storage).Prune: Error looking up candidates from remote storage! %w",
+				candidate.Err,
+			)
+		}
+		if candidate.LastModified.Before(deadline) {
+			matches = append(matches, candidate)
+		}
+	}
+
+	stats := &storage.PruneStats{
+		Total:  uint(lenCandidates),
+		Pruned: uint(len(matches)),
+	}
+
+	if err := b.DoPrune(b.Name(), len(matches), lenCandidates, "remote backup(s)", func() error {
+		objectsCh := make(chan minio.ObjectInfo)
+		go func() {
+			for _, match := range matches {
+				objectsCh <- match
+			}
+			close(objectsCh)
+		}()
+		errChan := b.client.RemoveObjects(context.Background(), b.bucket, objectsCh, minio.RemoveObjectsOptions{})
+		var removeErrors []error
+		for result := range errChan {
+			if result.Err != nil {
+				removeErrors = append(removeErrors, result.Err)
+			}
+		}
+		if len(removeErrors) != 0 {
+			return utilities.Join(removeErrors...)
+		}
+		return nil
+	}); err != nil {
+		return stats, err
+	}
+
+	return stats, nil
+}

internal/storage/ssh/ssh.go

@@ -0,0 +1,190 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package ssh
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/offen/docker-volume-backup/internal/storage"
+	"github.com/pkg/sftp"
+	"golang.org/x/crypto/ssh"
+)
+
+type sshStorage struct {
+	*storage.StorageBackend
+	client     *ssh.Client
+	sftpClient *sftp.Client
+	hostName   string
+}
+
+// Config allows to configure a SSH backend.
+type Config struct {
+	HostName           string
+	Port               string
+	User               string
+	Password           string
+	IdentityFile       string
+	IdentityPassphrase string
+	RemotePath         string
+}
+
+// NewStorageBackend creates and initializes a new SSH storage backend.
+func NewStorageBackend(opts Config, logFunc storage.Log) (storage.Backend, error) {
+	var authMethods []ssh.AuthMethod
+
+	if opts.Password != "" {
+		authMethods = append(authMethods, ssh.Password(opts.Password))
+	}
+
+	if _, err := os.Stat(opts.IdentityFile); err == nil {
+		key, err := ioutil.ReadFile(opts.IdentityFile)
+		if err != nil {
+			return nil, errors.New("NewStorageBackend: error reading the private key")
+		}
+
+		var signer ssh.Signer
+		if opts.IdentityPassphrase != "" {
+			signer, err = ssh.ParsePrivateKeyWithPassphrase(key, []byte(opts.IdentityPassphrase))
+			if err != nil {
+				return nil, errors.New("NewStorageBackend: error parsing the encrypted private key")
+			}
+			authMethods = append(authMethods, ssh.PublicKeys(signer))
+		} else {
+			signer, err = ssh.ParsePrivateKey(key)
+			if err != nil {
+				return nil, errors.New("NewStorageBackend: error parsing the private key")
+			}
+			authMethods = append(authMethods, ssh.PublicKeys(signer))
+		}
+	}
+
+	sshClientConfig := &ssh.ClientConfig{
+		User:            opts.User,
+		Auth:            authMethods,
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+	}
+	sshClient, err := ssh.Dial("tcp", fmt.Sprintf("%s:%s", opts.HostName, opts.Port), sshClientConfig)
+
+	if err != nil {
+		return nil, fmt.Errorf("NewStorageBackend: Error creating ssh client: %w", err)
+	}
+	_, _, err = sshClient.SendRequest("keepalive", false, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	sftpClient, err := sftp.NewClient(sshClient)
+	if err != nil {
+		return nil, fmt.Errorf("NewStorageBackend: error creating sftp client: %w", err)
+	}
+
+	return &sshStorage{
+		StorageBackend: &storage.StorageBackend{
+			DestinationPath: opts.RemotePath,
+			Log:             logFunc,
+		},
+		client:     sshClient,
+		sftpClient: sftpClient,
+		hostName:   opts.HostName,
+	}, nil
+}
+
+// Name returns the name of the storage backend
+func (b *sshStorage) Name() string {
+	return "SSH"
+}
+
+// Copy copies the given file to the SSH storage backend.
+func (b *sshStorage) Copy(file string) error {
+	source, err := os.Open(file)
+	_, name := path.Split(file)
+	if err != nil {
+		return fmt.Errorf("(*sshStorage).Copy: Error reading the file to be uploaded: %w", err)
+	}
+	defer source.Close()
+
+	destination, err := b.sftpClient.Create(filepath.Join(b.DestinationPath, name))
+	if err != nil {
+		return fmt.Errorf("(*sshStorage).Copy: Error creating file on SSH storage: %w", err)
+	}
+	defer destination.Close()
+
+	chunk := make([]byte, 1000000)
+	for {
+		num, err := source.Read(chunk)
+		if err == io.EOF {
+			tot, err := destination.Write(chunk[:num])
+			if err != nil {
+				return fmt.Errorf("(*sshStorage).Copy: Error uploading the file to SSH storage: %w", err)
+			}
+
+			if tot != len(chunk[:num]) {
+				return errors.New("(*sshStorage).Copy: failed to write stream")
+			}
+
+			break
+		}
+
+		if err != nil {
+			return fmt.Errorf("(*sshStorage).Copy: Error uploading the file to SSH storage: %w", err)
+		}
+
+		tot, err := destination.Write(chunk[:num])
+		if err != nil {
+			return fmt.Errorf("(*sshStorage).Copy: Error uploading the file to SSH storage: %w", err)
+		}
+
+		if tot != len(chunk[:num]) {
+			return fmt.Errorf("(*sshStorage).Copy: failed to write stream")
+		}
+	}
+
+	b.Log(storage.LogLevelInfo, b.Name(), "Uploaded a copy of backup `%s` to SSH storage '%s' at path '%s'.", file, b.hostName, b.DestinationPath)
+
+	return nil
+}
+
+// Prune rotates away backups according to the configuration and provided deadline for the SSH storage backend.
+func (b *sshStorage) Prune(deadline time.Time, pruningPrefix string) (*storage.PruneStats, error) {
+	candidates, err := b.sftpClient.ReadDir(b.DestinationPath)
+	if err != nil {
+		return nil, fmt.Errorf("(*sshStorage).Prune: Error reading directory from SSH storage: %w", err)
+	}
+
+	var matches []string
+	for _, candidate := range candidates {
+		if !strings.HasPrefix(candidate.Name(), pruningPrefix) {
+			continue
+		}
+		if candidate.ModTime().Before(deadline) {
+			matches = append(matches, candidate.Name())
+		}
+	}
+
+	stats := &storage.PruneStats{
+		Total:  uint(len(candidates)),
+		Pruned: uint(len(matches)),
+	}
+
+	if err := b.DoPrune(b.Name(), len(matches), len(candidates), "SSH backup(s)", func() error {
+		for _, match := range matches {
+			if err := b.sftpClient.Remove(filepath.Join(b.DestinationPath, match)); err != nil {
+				return fmt.Errorf("(*sshStorage).Prune: Error removing file from SSH storage: %w", err)
+			}
+		}
+		return nil
+	}); err != nil {
+		return stats, err
+	}
+
+	return stats, nil
+}

internal/storage/storage.go

@@ -0,0 +1,61 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package storage
+
+import (
+	"time"
+)
+
+// Backend is an interface for defining functions which all storage providers support.
+type Backend interface {
+	Copy(file string) error
+	Prune(deadline time.Time, pruningPrefix string) (*PruneStats, error)
+	Name() string
+}
+
+// StorageBackend is a generic type of storage. Everything here are common properties of all storage types.
+type StorageBackend struct {
+	DestinationPath string
+	RetentionDays   int
+	Log             Log
+}
+
+type LogLevel int
+
+const (
+	LogLevelInfo LogLevel = iota
+	LogLevelWarning
+	LogLevelError
+)
+
+type Log func(logType LogLevel, context string, msg string, params ...interface{})
+
+// PruneStats is a wrapper struct for returning stats after pruning
+type PruneStats struct {
+	Total  uint
+	Pruned uint
+}
+
+// DoPrune holds general control flow that applies to any kind of storage.
+// Callers can pass in a thunk that performs the actual deletion of files.
+func (b *StorageBackend) DoPrune(context string, lenMatches, lenCandidates int, description string, doRemoveFiles func() error) error {
+	if lenMatches != 0 && lenMatches != lenCandidates {
+		if err := doRemoveFiles(); err != nil {
+			return err
+		}
+		b.Log(LogLevelInfo, context,
+			"Pruned %d out of %d %s as their age exceeded the configured retention period of %d days.",
+			lenMatches,
+			lenCandidates,
+			description,
+			b.RetentionDays,
+		)
+	} else if lenMatches != 0 && lenMatches == lenCandidates {
+		b.Log(LogLevelWarning, context, "The current configuration would delete all %d existing %s.", lenMatches, description)
+		b.Log(LogLevelWarning, context, "Refusing to do so, please check your configuration.")
+	} else {
+		b.Log(LogLevelInfo, context, "None of %d existing %s were pruned.", lenCandidates, description)
+	}
+	return nil
+}

internal/storage/webdav/webdav.go

@@ -0,0 +1,121 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package webdav
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/offen/docker-volume-backup/internal/storage"
+	"github.com/studio-b12/gowebdav"
+)
+
+type webDavStorage struct {
+	*storage.StorageBackend
+	client *gowebdav.Client
+	url    string
+}
+
+// Config allows to configure a WebDAV storage backend.
+type Config struct {
+	URL         string
+	RemotePath  string
+	Username    string
+	Password    string
+	URLInsecure bool
+}
+
+// NewStorageBackend creates and initializes a new WebDav storage backend.
+func NewStorageBackend(opts Config, logFunc storage.Log) (storage.Backend, error) {
+	if opts.Username == "" || opts.Password == "" {
+		return nil, errors.New("NewStorageBackend: WEBDAV_URL is defined, but no credentials were provided")
+	} else {
+		webdavClient := gowebdav.NewClient(opts.URL, opts.Username, opts.Password)
+
+		if opts.URLInsecure {
+			defaultTransport, ok := http.DefaultTransport.(*http.Transport)
+			if !ok {
+				return nil, errors.New("NewStorageBackend: unexpected error when asserting type for http.DefaultTransport")
+			}
+			webdavTransport := defaultTransport.Clone()
+			webdavTransport.TLSClientConfig.InsecureSkipVerify = opts.URLInsecure
+			webdavClient.SetTransport(webdavTransport)
+		}
+
+		return &webDavStorage{
+			StorageBackend: &storage.StorageBackend{
+				DestinationPath: opts.RemotePath,
+				Log:             logFunc,
+			},
+			client: webdavClient,
+		}, nil
+	}
+}
+
+// Name returns the name of the storage backend
+func (b *webDavStorage) Name() string {
+	return "WebDAV"
+}
+
+// Copy copies the given file to the WebDav storage backend.
+func (b *webDavStorage) Copy(file string) error {
+	bytes, err := os.ReadFile(file)
+	_, name := path.Split(file)
+	if err != nil {
+		return fmt.Errorf("(*webDavStorage).Copy: Error reading the file to be uploaded: %w", err)
+	}
+	if err := b.client.MkdirAll(b.DestinationPath, 0644); err != nil {
+		return fmt.Errorf("(*webDavStorage).Copy: Error creating directory '%s' on WebDAV server: %w", b.DestinationPath, err)
+	}
+	if err := b.client.Write(filepath.Join(b.DestinationPath, name), bytes, 0644); err != nil {
+		return fmt.Errorf("(*webDavStorage).Copy: Error uploading the file to WebDAV server: %w", err)
+	}
+	b.Log(storage.LogLevelInfo, b.Name(), "Uploaded a copy of backup '%s' to WebDAV URL '%s' at path '%s'.", file, b.url, b.DestinationPath)
+
+	return nil
+}
+
+// Prune rotates away backups according to the configuration and provided deadline for the WebDav storage backend.
+func (b *webDavStorage) Prune(deadline time.Time, pruningPrefix string) (*storage.PruneStats, error) {
+	candidates, err := b.client.ReadDir(b.DestinationPath)
+	if err != nil {
+		return nil, fmt.Errorf("(*webDavStorage).Prune: Error looking up candidates from remote storage: %w", err)
+	}
+	var matches []fs.FileInfo
+	var lenCandidates int
+	for _, candidate := range candidates {
+		if !strings.HasPrefix(candidate.Name(), pruningPrefix) {
+			continue
+		}
+		lenCandidates++
+		if candidate.ModTime().Before(deadline) {
+			matches = append(matches, candidate)
+		}
+	}
+
+	stats := &storage.PruneStats{
+		Total:  uint(lenCandidates),
+		Pruned: uint(len(matches)),
+	}
+
+	if err := b.DoPrune(b.Name(), len(matches), lenCandidates, "WebDAV backup(s)", func() error {
+		for _, match := range matches {
+			if err := b.client.Remove(filepath.Join(b.DestinationPath, match.Name())); err != nil {
+				return fmt.Errorf("(*webDavStorage).Prune: Error removing file from WebDAV storage: %w", err)
+			}
+		}
+		return nil
+	}); err != nil {
+		return stats, err
+	}
+
+	return stats, nil
+}

internal/utilities/util.go

@@ -0,0 +1,24 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package utilities
+
+import (
+	"errors"
+	"strings"
+)
+
+// Join takes a list of errors and joins them into a single error
+func Join(errs ...error) error {
+	if len(errs) == 1 {
+		return errs[0]
+	}
+	var msgs []string
+	for _, err := range errs {
+		if err == nil {
+			continue
+		}
+		msgs = append(msgs, err.Error())
+	}
+	return errors.New("[" + strings.Join(msgs, ", ") + "]")
+}

test/cli/run.sh

@@ -3,10 +3,15 @@
 set -e
 
 cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
 
 docker network create test_network
 docker volume create backup_data
 docker volume create app_data
+# This volume is created to test whether empty directories are handled
+# correctly. It is not supposed to hold any data.
+docker volume create empty_data
 
 docker run -d \
   --name minio \
@@ -23,7 +28,6 @@ docker exec minio mkdir -p /data/backup
 docker run -d \
   --name offen \
   --network test_network \
-  --label "docker-volume-backup.stop-during-backup=true" \
   -v app_data:/var/opt/offen/ \
   offen/offen:latest
 
@@ -32,6 +36,7 @@ sleep 10
 docker run --rm \
   --network test_network \
   -v app_data:/backup/app_data \
+  -v empty_data:/backup/empty_data \
   -v /var/run/docker.sock:/var/run/docker.sock \
   --env AWS_ACCESS_KEY_ID=test \
   --env AWS_SECRET_ACCESS_KEY=GMusLtUmILge2by+z890kQ \
@@ -39,23 +44,20 @@ docker run --rm \
   --env AWS_ENDPOINT_PROTO=http \
   --env AWS_S3_BUCKET_NAME=backup \
   --env BACKUP_FILENAME=test.tar.gz \
+  --env "BACKUP_FROM_SNAPSHOT=true" \
   --entrypoint backup \
-  offen/docker-volume-backup:$TEST_VERSION
+  offen/docker-volume-backup:${TEST_VERSION:-canary}
 
 docker run --rm -it \
   -v backup_data:/data alpine \
-  ash -c 'tar -xvf /data/backup/test.tar.gz && test -f /backup/app_data/offen.db'
+  ash -c 'tar -xvf /data/backup/test.tar.gz && test -f /backup/app_data/offen.db && test -d /backup/empty_data'
 
-echo "[TEST:PASS] Found relevant files in untared backup."
+pass "Found relevant files in untared remote backup."
 
-if [ "$(docker ps -q | wc -l)" != "2" ]; then
-  echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
-  docker ps
-  exit 1
-fi
+# This test does not stop containers during backup. This is happening on
+# purpose in order to cover this setup as well.
+expect_running_containers "2"
 
-echo "[TEST:PASS] All containers running post backup."
-
-docker rm $(docker stop minio offen backup)
+docker rm $(docker stop minio offen)
 docker volume rm backup_data app_data
 docker network rm test_network

test/commands/docker-compose.yml

@@ -0,0 +1,51 @@
+version: '3.8'
+
+services:
+  database:
+    image: mariadb:10.7
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      MARIADB_ROOT_PASSWORD: test
+      MARIADB_DATABASE: backup
+    labels:
+      # this is testing the deprecated label on purpose
+      - docker-volume-backup.exec-pre=/bin/sh -c 'mysqldump -ptest --all-databases > /tmp/volume/dump.sql'
+      - docker-volume-backup.copy-post=/bin/sh -c 'echo "post" > /tmp/volume/post.txt'
+      - docker-volume-backup.exec-label=test
+    volumes:
+      - app_data:/tmp/volume
+
+  other_database:
+    image: mariadb:10.7
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      MARIADB_ROOT_PASSWORD: test
+      MARIADB_DATABASE: backup
+    labels:
+      - docker-volume-backup.archive-pre=touch /tmp/volume/not-relevant.txt
+      - docker-volume-backup.exec-label=not-relevant
+    volumes:
+      - app_data:/tmp/volume
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      EXEC_LABEL: test
+      EXEC_FORWARD_OUTPUT: "true"
+    volumes:
+      - archive:/archive
+      - app_data:/backup/data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+volumes:
+  app_data:
+  archive:

test/commands/run.sh

@@ -0,0 +1,64 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+docker-compose up -d
+sleep 30 # mariadb likes to take a bit before responding
+
+docker-compose exec backup backup
+sudo cp -r $(docker volume inspect --format='{{ .Mountpoint }}' commands_archive) ./local
+
+tar -xvf ./local/test.tar.gz
+if [ ! -f ./backup/data/dump.sql ]; then
+  fail "Could not find file written by pre command."
+fi
+pass "Found expected file."
+
+if [ -f ./backup/data/not-relevant.txt ]; then
+  fail "Command ran for container with other label."
+fi
+pass "Command did not run for container with other label."
+
+if [ -f ./backup/data/post.txt ]; then
+  fail "File created in post command was present in backup."
+fi
+pass "Did not find unexpected file."
+
+docker-compose down --volumes
+sudo rm -rf ./local
+
+
+info "Running commands test in swarm mode next."
+
+docker swarm init
+
+docker stack deploy --compose-file=docker-compose.yml test_stack
+
+while [ -z $(docker ps -q -f name=backup) ]; do
+  info "Backup container not ready yet. Retrying."
+  sleep 1
+done
+
+sleep 20
+
+docker exec $(docker ps -q -f name=backup) backup
+
+sudo cp -r $(docker volume inspect --format='{{ .Mountpoint }}' test_stack_archive) ./local
+
+tar -xvf ./local/test.tar.gz
+if [ ! -f ./backup/data/dump.sql ]; then
+  fail "Could not find file written by pre command."
+fi
+pass "Found expected file."
+
+if [ -f ./backup/data/post.txt ]; then
+  fail "File created in post command was present in backup."
+fi
+pass "Did not find unexpected file."
+
+docker stack rm test_stack
+docker swarm leave --force

test/compose/run.sh

@@ -1,57 +0,0 @@
-#!/bin/sh
-
-set -e
-
-cd $(dirname $0)
-
-mkdir -p local
-
-docker-compose up -d
-sleep 5
-
-docker-compose exec offen ln -s /var/opt/offen/offen.db /var/opt/offen/db.link
-docker-compose exec backup backup
-
-docker run --rm -it \
-  -v compose_backup_data:/data alpine \
-  ash -c 'apk add gnupg && echo 1234secret | gpg -d --pinentry-mode loopback --passphrase-fd 0 --yes /data/backup/test.tar.gz.gpg > /tmp/test.tar.gz && tar -xf /tmp/test.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
-
-echo "[TEST:PASS] Found relevant files in untared remote backup."
-
-echo 1234secret | gpg -d --yes --passphrase-fd 0 ./local/test.tar.gz.gpg > ./local/decrypted.tar.gz
-tar -xf ./local/decrypted.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db
-rm ./local/decrypted.tar.gz
-test -L /tmp/backup/app_data/db.link
-
-echo "[TEST:PASS] Found relevant files in untared local backup."
-
-if [ "$(docker-compose ps -q | wc -l)" != "3" ]; then
-  echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
-  docker-compose ps
-  exit 1
-fi
-
-echo "[TEST:PASS] All containers running post backup."
-
-# The second part of this test checks if backups get deleted when the retention
-# is set to 0 days (which it should not as it would mean all backups get deleted)
-# TODO: find out if we can test actual deletion without having to wait for a day
-BACKUP_RETENTION_DAYS="0" docker-compose up -d
-sleep 5
-
-docker-compose exec backup backup
-
-docker run --rm -it \
-  -v compose_backup_data:/data alpine \
-  ash -c '[ $(find /data/backup/ -type f | wc -l) = "1" ]'
-
-echo "[TEST:PASS] Remote backups have not been deleted."
-
-if [ "$(find ./local -type f | wc -l)" != "1" ]; then
-  echo "[TEST:FAIL] Backups should not have been deleted, instead seen:"
-  find ./local -type f
-fi
-
-echo "[TEST:PASS] Local backups have not been deleted."
-
-docker-compose down --volumes

test/confd/.gitignore

@@ -0,0 +1 @@
+local

test/confd/01backup.env

@@ -0,0 +1,2 @@
+BACKUP_FILENAME="conf.tar.gz"
+BACKUP_CRON_EXPRESSION="*/1 * * * *"

test/confd/02backup.env

@@ -0,0 +1,2 @@
+BACKUP_FILENAME="other.tar.gz"
+BACKUP_CRON_EXPRESSION="*/1 * * * *"

test/confd/03never.env

@@ -0,0 +1,2 @@
+BACKUP_FILENAME="never.tar.gz"
+BACKUP_CRON_EXPRESSION="0 0 5 31 2 ?"

test/confd/docker-compose.yml

@@ -0,0 +1,23 @@
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    restart: always
+    volumes:
+      - ./local:/archive
+      - app_data:/backup/app_data:ro
+      - ./01backup.env:/etc/dockervolumebackup/conf.d/01backup.env
+      - ./02backup.env:/etc/dockervolumebackup/conf.d/02backup.env
+      - ./03never.env:/etc/dockervolumebackup/conf.d/03never.env
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  app_data:

test/confd/run.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+
+# sleep until a backup is guaranteed to have happened on the 1 minute schedule
+sleep 100
+
+docker-compose down --volumes
+
+if [ ! -f ./local/conf.tar.gz ]; then
+  fail "Config from file was not used."
+fi
+pass "Config from file was used."
+
+if [ ! -f ./local/other.tar.gz ]; then
+  fail "Run on same schedule did not succeed."
+fi
+pass "Run on same schedule succeeded."
+
+if [ -f ./local/never.tar.gz ]; then
+  fail "Unexpected file was found."
+fi
+pass "Unexpected cron did not run."

test/gpg/.gitignore

@@ -0,0 +1 @@
+local

test/gpg/docker-compose.yml

@@ -0,0 +1,26 @@
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    restart: always
+    environment:
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_LATEST_SYMLINK: test-latest.tar.gz.gpg
+      BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
+      GPG_PASSPHRASE: 1234secret
+    volumes:
+      - ./local:/archive
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  app_data:

test/gpg/run.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+expect_running_containers "2"
+
+tmp_dir=$(mktemp -d)
+
+echo 1234secret | gpg -d --pinentry-mode loopback --yes --passphrase-fd 0 ./local/test.tar.gz.gpg > ./local/decrypted.tar.gz
+tar -xf ./local/decrypted.tar.gz -C $tmp_dir
+ls -lah $tmp_dir
+if [ ! -f $tmp_dir/backup/app_data/offen.db ]; then
+  fail "Could not find expected file in untared archive."
+fi
+rm ./local/decrypted.tar.gz
+
+pass "Found relevant files in decrypted and untared local backup."
+
+if [ ! -L ./local/test-latest.tar.gz.gpg ]; then
+  fail "Could not find local symlink to latest encrypted backup."
+fi
+
+docker-compose down --volumes

test/ignore/.gitignore

@@ -0,0 +1 @@
+local

test/ignore/docker-compose.yml

@@ -0,0 +1,15 @@
+version: '3.8'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_EXCLUDE_REGEXP: '\.(me|you)$$'
+    volumes:
+      - ./local:/archive
+      - ./sources:/backup/data:ro

test/ignore/run.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+docker-compose exec backup backup
+
+docker-compose down --volumes
+
+out=$(mktemp -d)
+sudo tar --same-owner -xvf ./local/test.tar.gz -C "$out"
+
+if [ ! -f "$out/backup/data/me.txt" ]; then
+  fail "Expected file was not found."
+fi
+pass "Expected file was found."
+
+if [ -f "$out/backup/data/skip.me" ]; then
+  fail "Ignored file was found."
+fi
+pass "Ignored file was not found."

test/local/.gitignore

@@ -0,0 +1 @@
+local

test/local/docker-compose.yml

@@ -0,0 +1,29 @@
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    hostname: hostnametoken
+    restart: always
+    environment:
+      BACKUP_FILENAME_EXPAND: 'true'
+      BACKUP_FILENAME: test-$$HOSTNAME.tar.gz
+      BACKUP_LATEST_SYMLINK: test-$$HOSTNAME.latest.tar.gz.gpg
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
+      BACKUP_PRUNING_LEEWAY: 5s
+      BACKUP_PRUNING_PREFIX: test
+    volumes:
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+      - ./local:/archive
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  app_data:

test/local/run.sh

@@ -0,0 +1,55 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+# A symlink for a known file in the volume is created so the test can check
+# whether symlinks are preserved on backup.
+docker-compose exec offen ln -s /var/opt/offen/offen.db /var/opt/offen/db.link
+docker-compose exec backup backup
+
+sleep 5
+
+expect_running_containers "2"
+
+tmp_dir=$(mktemp -d)
+tar -xvf ./local/test-hostnametoken.tar.gz -C $tmp_dir
+if [ ! -f "$tmp_dir/backup/app_data/offen.db" ]; then
+  fail "Could not find expected file in untared archive."
+fi
+rm -f ./local/test-hostnametoken.tar.gz
+
+if [ ! -L "$tmp_dir/backup/app_data/db.link" ]; then
+  fail "Could not find expected symlink in untared archive."
+fi
+
+pass "Found relevant files in decrypted and untared local backup."
+
+if [ ! -L ./local/test-hostnametoken.latest.tar.gz.gpg ]; then
+  fail "Could not find symlink to latest version."
+fi
+
+pass "Found symlink to latest version in local backup."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+# TODO: find out if we can test actual deletion without having to wait for a day
+BACKUP_RETENTION_DAYS="0" docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+if [ "$(find ./local -type f | wc -l)" != "1" ]; then
+  fail "Backups should not have been deleted, instead seen: "$(find ./local -type f)""
+fi
+pass "Local backups have not been deleted."
+
+docker-compose down --volumes

test/notifications/.gitignore

@@ -0,0 +1 @@
+local

test/notifications/docker-compose.yml

@@ -0,0 +1,37 @@
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    restart: always
+    environment:
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_PRUNING_PREFIX: test
+      NOTIFICATION_LEVEL: info
+      NOTIFICATION_URLS: ${NOTIFICATION_URLS}
+      EXTRA_VALUE: extra-value
+    volumes:
+      - ./local:/archive
+      - app_data:/backup/app_data:ro
+      - ./notifications.tmpl:/etc/dockervolumebackup/notifications.d/notifications.tmpl
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+  gotify:
+    image: gotify/server
+    ports:
+      - 8080:80
+    environment:
+      - GOTIFY_DEFAULTUSER_PASS=custom
+    volumes:
+      - gotify_data:/app/data
+
+volumes:
+  app_data:
+  gotify_data:

test/notifications/notifications.tmpl

@@ -0,0 +1,7 @@
+{{ define "title_success" -}}
+Successful test run with {{ env "EXTRA_VALUE" }}, yay!
+{{- end }}
+
+{{ define "body_success" -}}
+Backing up {{ .Stats.BackupFile.FullPath }} succeeded.
+{{- end }}

test/notifications/run.sh

@@ -0,0 +1,50 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+GOTIFY_TOKEN=$(curl -sSLX POST -H 'Content-Type: application/json' -d '{"name":"test"}' http://admin:custom@localhost:8080/application | jq -r '.token')
+info "Set up Gotify application using token $GOTIFY_TOKEN"
+
+docker-compose exec backup backup
+
+NUM_MESSAGES=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages | length')
+if [ "$NUM_MESSAGES" != 0 ]; then
+  fail "Expected no notifications to be sent when not configured"
+fi
+pass "No notifications were sent when not configured."
+
+docker-compose down
+
+NOTIFICATION_URLS="gotify://gotify/${GOTIFY_TOKEN}?disableTLS=true" docker-compose up -d
+
+docker-compose exec backup backup
+
+NUM_MESSAGES=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages | length')
+if [ "$NUM_MESSAGES" != 1 ]; then
+  fail "Expected one notifications to be sent when configured"
+fi
+pass "Correct number of notifications were sent when configured."
+
+MESSAGE_TITLE=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages[0].title')
+MESSAGE_BODY=$(curl -sSL http://admin:custom@localhost:8080/message | jq -r '.messages[0].message')
+
+if [ "$MESSAGE_TITLE" != "Successful test run with extra-value, yay!" ]; then
+  fail "Unexpected notification title $MESSAGE_TITLE"
+fi
+pass "Custom notification title was used."
+
+if [ "$MESSAGE_BODY" != "Backing up /tmp/test.tar.gz succeeded." ]; then
+  fail "Unexpected notification body $MESSAGE_BODY"
+fi
+pass "Custom notification body was used."
+
+docker-compose down --volumes

test/ownership/.gitignore

@@ -0,0 +1 @@
+local

test/ownership/docker-compose.yml

@@ -0,0 +1,27 @@
+version: '3'
+
+services:
+  db:
+    image: postgres:14-alpine
+    restart: unless-stopped
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    environment:
+      - POSTGRES_PASSWORD=1FHJMSwt0yhIN1zS7I4DilGUhThBKq0x
+      - POSTGRES_USER=test
+      - POSTGRES_DB=test
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION}
+    restart: always
+    environment:
+      BACKUP_FILENAME: backup.tar.gz
+    volumes:
+      - postgres_data:/backup/postgres:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - ./local:/archive
+
+volumes:
+  postgres_data:

test/ownership/run.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+# This test refers to https://github.com/offen/docker-volume-backup/issues/71
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+tmp_dir=$(mktemp -d)
+sudo tar --same-owner -xvf ./local/backup.tar.gz -C $tmp_dir
+
+sudo find $tmp_dir/backup/postgres > /dev/null
+pass "Backup contains files at expected location"
+
+for file in $(sudo find $tmp_dir/backup/postgres); do
+  if [ "$(sudo stat -c '%u:%g' $file)" != "70:70" ]; then
+    fail "Unexpected file ownership for $file: $(sudo stat -c '%u:%g' $file)"
+  fi
+done
+pass "All files and directories in backup preserved their ownership."
+
+docker-compose down --volumes

test/s3/docker-compose.yml

@@ -10,10 +10,11 @@ services:
       MINIO_SECRET_KEY: GMusLtUmILge2by+z890kQ
     entrypoint: /bin/ash -c 'mkdir -p /data/backup && minio server /data'
     volumes:
-      - backup_data:/data
+      - minio_backup_data:/data
 
-  backup: &default_backup_service
-    image: offen/docker-volume-backup:${TEST_VERSION}
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    hostname: hostnametoken
     depends_on:
       - minio
     restart: always
@@ -23,14 +24,13 @@ services:
       AWS_ENDPOINT: minio:9000
       AWS_ENDPOINT_PROTO: http
       AWS_S3_BUCKET_NAME: backup
-      BACKUP_FILENAME: test.tar.gz
+      BACKUP_FILENAME_EXPAND: 'true'
+      BACKUP_FILENAME: test-$$HOSTNAME.tar.gz
       BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
       BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
       BACKUP_PRUNING_LEEWAY: 5s
       BACKUP_PRUNING_PREFIX: test
-      GPG_PASSPHRASE: 1234secret
     volumes:
-      - ./local:/archive
       - app_data:/backup/app_data:ro
       - /var/run/docker.sock:/var/run/docker.sock
 
@@ -42,5 +42,6 @@ services:
       - app_data:/var/opt/offen
 
 volumes:
-  backup_data:
+  minio_backup_data:
+    name: minio_backup_data
   app_data:

test/s3/run.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+docker-compose up -d
+sleep 5
+
+# A symlink for a known file in the volume is created so the test can check
+# whether symlinks are preserved on backup.
+docker-compose exec backup backup
+
+sleep 5
+
+expect_running_containers "3"
+
+docker run --rm -it \
+  -v minio_backup_data:/minio_data \
+  alpine \
+  ash -c 'tar -xvf /minio_data/backup/test-hostnametoken.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
+
+pass "Found relevant files in untared remote backups."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+# TODO: find out if we can test actual deletion without having to wait for a day
+BACKUP_RETENTION_DAYS="0" docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+docker run --rm -it \
+  -v minio_backup_data:/minio_data \
+  alpine \
+  ash -c '[ $(find /minio_data/backup/ -type f | wc -l) = "1" ]'
+
+pass "Remote backups have not been deleted."
+
+docker-compose down --volumes

test/secret/docker-compose.yml

@@ -0,0 +1,89 @@
+# Copyright 2020-2021 - Offen Authors <hioffen@posteo.de>
+# SPDX-License-Identifier: Unlicense
+
+version: '3.8'
+
+services:
+  minio_setup:
+    image: alpine:latest
+    deploy:
+      restart_policy:
+        condition: none
+    volumes:
+      - backup_data:/data
+    command: mkdir -p /data/backup
+    
+  minio:
+    image: minio/minio:RELEASE.2021-12-20T22-07-16Z
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      MINIO_ROOT_USER_FILE: /run/secrets/minio_root_user
+      MINIO_ROOT_PASSWORD_FILE: /run/secrets/minio_root_password
+    command: minio server /data
+    volumes:
+      - backup_data:/data
+    secrets:
+      - minio_root_user
+      - minio_root_password
+    depends_on:
+      - minio_setup
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    depends_on:
+      - minio
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      AWS_ACCESS_KEY_ID_FILE: /run/secrets/minio_root_user
+      AWS_SECRET_ACCESS_KEY_FILE: /run/secrets/minio_root_password
+      AWS_ENDPOINT: minio:9000
+      AWS_ENDPOINT_PROTO: http
+      AWS_S3_BUCKET_NAME: backup
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_RETENTION_DAYS: 7
+      BACKUP_PRUNING_LEEWAY: 5s
+    volumes:
+      - pg_data:/backup/pg_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+    secrets:
+      - minio_root_user
+      - minio_root_password
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    healthcheck:
+      disable: true
+    deploy:
+      replicas: 2
+      restart_policy:
+        condition: on-failure
+
+  pg:
+    image: postgres:14-alpine
+    environment:
+      POSTGRES_PASSWORD: example
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - pg_data:/var/lib/postgresql/data
+    deploy:
+      restart_policy:
+        condition: on-failure
+
+volumes:
+  backup_data:
+    name: backup_data
+  pg_data:
+
+secrets:
+  minio_root_user:
+    external: true
+  minio_root_password:
+    external: true

test/secret/run.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+docker swarm init
+
+printf "test" | docker secret create minio_root_user -
+printf "GMusLtUmILge2by+z890kQ" | docker secret create minio_root_password -
+
+docker stack deploy --compose-file=docker-compose.yml test_stack
+
+while [ -z $(docker ps -q -f name=backup) ]; do
+  info "Backup container not ready yet. Retrying."
+  sleep 1
+done
+
+sleep 20
+
+docker exec $(docker ps -q -f name=backup) backup
+
+docker run --rm -it \
+  -v backup_data:/data alpine \
+  ash -c 'tar -xf /data/backup/test.tar.gz && test -f /backup/pg_data/PG_VERSION'
+
+pass "Found relevant files in untared backup."
+
+sleep 5
+expect_running_containers "5"
+
+docker stack rm test_stack
+
+docker secret rm minio_root_password
+docker secret rm minio_root_user
+
+docker swarm leave --force
+
+sleep 10
+
+docker volume rm backup_data
+docker volume rm test_stack_pg_data

test/ssh/docker-compose.yml

@@ -0,0 +1,47 @@
+version: '3'
+
+services:
+  ssh:
+    image: linuxserver/openssh-server:version-8.6_p1-r3
+    environment:
+      - PUID=1000
+      - PGID=1000
+      - USER_NAME=test
+    volumes:
+      - ./id_rsa.pub:/config/.ssh/authorized_keys
+      - ssh_backup_data:/tmp
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    hostname: hostnametoken
+    depends_on:
+      - ssh
+    restart: always
+    environment:
+      BACKUP_FILENAME_EXPAND: 'true'
+      BACKUP_FILENAME: test-$$HOSTNAME.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
+      BACKUP_PRUNING_LEEWAY: 5s
+      BACKUP_PRUNING_PREFIX: test
+      SSH_HOST_NAME: ssh
+      SSH_PORT: 2222
+      SSH_USER: test
+      SSH_REMOTE_PATH: /tmp
+      SSH_IDENTITY_PASSPHRASE: test1234
+    volumes:
+      - ./id_rsa:/root/.ssh/id_rsa
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  ssh_backup_data:
+    name: ssh_backup_data
+  app_data:

test/ssh/run.sh

@@ -0,0 +1,43 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+ssh-keygen -t rsa -m pem -b 4096 -N "test1234" -f id_rsa -C "docker-volume-backup@local"
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+sleep 5
+
+expect_running_containers 3
+
+docker run --rm -it \
+  -v ssh_backup_data:/ssh_data \
+  alpine \
+  ash -c 'tar -xvf /ssh_data/test-hostnametoken.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
+
+pass "Found relevant files in decrypted and untared remote backups."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+# TODO: find out if we can test actual deletion without having to wait for a day
+BACKUP_RETENTION_DAYS="0" docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+docker run --rm -it \
+  -v ssh_backup_data:/ssh_data \
+  alpine \
+  ash -c '[ $(find /ssh_data/ -type f | wc -l) = "1" ]'
+
+pass "Remote backups have not been deleted."
+
+docker-compose down --volumes
+rm -f id_rsa id_rsa.pub

test/swarm/docker-compose.yml

@@ -18,8 +18,8 @@ services:
     volumes:
       - backup_data:/data
 
-  backup: &default_backup_service
-    image: offen/docker-volume-backup:${TEST_VERSION}
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
     depends_on:
       - minio
     deploy:
@@ -43,13 +43,15 @@ services:
     image: offen/offen:latest
     labels:
       - docker-volume-backup.stop-during-backup=true
+    healthcheck:
+      disable: true
     deploy:
       replicas: 2
       restart_policy:
         condition: on-failure
 
   pg:
-    image: postgres:12.2-alpine
+    image: postgres:14-alpine
     environment:
       POSTGRES_PASSWORD: example
     labels:
@@ -62,4 +64,5 @@ services:
 
 volumes:
   backup_data:
+    name: backup_data
   pg_data:

test/swarm/run.sh

@@ -3,13 +3,15 @@
 set -e
 
 cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
 
 docker swarm init
 
 docker stack deploy --compose-file=docker-compose.yml test_stack
 
 while [ -z $(docker ps -q -f name=backup) ]; do
-  echo "[TEST:INFO] Backup container not ready yet. Retrying."
+  info "Backup container not ready yet. Retrying."
   sleep 1
 done
 
@@ -18,19 +20,18 @@ sleep 20
 docker exec $(docker ps -q -f name=backup) backup
 
 docker run --rm -it \
-  -v test_stack_backup_data:/data alpine \
+  -v backup_data:/data alpine \
   ash -c 'tar -xf /data/backup/test.tar.gz && test -f /backup/pg_data/PG_VERSION'
 
-echo "[TEST:PASS] Found relevant files in untared backup."
+pass "Found relevant files in untared backup."
 
-if [ "$(docker ps -q | wc -l)" != "5" ]; then
-  echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
-  docker ps -a
-  exit 1
-fi
-
-echo "[TEST:PASS] All containers running post backup."
+sleep 5
+expect_running_containers "5"
 
 docker stack rm test_stack
-
 docker swarm leave --force
+
+sleep 10
+
+docker volume rm backup_data
+docker volume rm test_stack_pg_data

test/util.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+set -e
+
+info () {
+  echo "[test:${current_test:-none}:info] "$1""
+}
+
+pass () {
+  echo "[test:${current_test:-none}:pass] "$1""
+}
+
+fail () {
+  echo "[test:${current_test:-none}:fail] "$1""
+  exit 1
+}
+
+expect_running_containers () {
+  if [ "$(docker ps -q | wc -l)" != "$1" ]; then
+    fail "Expected $1 containers to be running, instead seen: "$(docker ps -a | wc -l)""
+  fi
+  pass "$1 containers running."
+}

test/webdav/docker-compose.yml

@@ -0,0 +1,45 @@
+version: '3'
+
+services:
+  webdav:
+    image: bytemark/webdav:2.4
+    environment:
+      AUTH_TYPE: Digest
+      USERNAME: test
+      PASSWORD: test
+    volumes:
+      - webdav_backup_data:/var/lib/dav
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    hostname: hostnametoken
+    depends_on:
+      - webdav
+    restart: always
+    environment:
+      BACKUP_FILENAME_EXPAND: 'true'
+      BACKUP_FILENAME: test-$$HOSTNAME.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
+      BACKUP_PRUNING_LEEWAY: 5s
+      BACKUP_PRUNING_PREFIX: test
+      WEBDAV_URL: http://webdav/
+      WEBDAV_URL_INSECURE: 'true'
+      WEBDAV_PATH: /my/new/path/
+      WEBDAV_USERNAME: test
+      WEBDAV_PASSWORD: test
+    volumes:
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  webdav_backup_data:
+    name: webdav_backup_data
+  app_data:

test/webdav/run.sh

@@ -0,0 +1,40 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+sleep 5
+
+expect_running_containers "3"
+
+docker run --rm -it \
+  -v webdav_backup_data:/webdav_data \
+  alpine \
+  ash -c 'tar -xvf /webdav_data/data/my/new/path/test-hostnametoken.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
+
+pass "Found relevant files in untared remote backup."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+# TODO: find out if we can test actual deletion without having to wait for a day
+BACKUP_RETENTION_DAYS="0" docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+docker run --rm -it \
+  -v webdav_backup_data:/webdav_data \
+  alpine \
+  ash -c '[ $(find /webdav_data/data/my/new/path/ -type f | wc -l) = "1" ]'
+
+pass "Remote backups have not been deleted."
+
+docker-compose down --volumes