Supporting proxied Docker APIs through DOCKER_HOST (#70)

* Split code into multiple files

* Deduplicate logic for pruning backups against different storages

* Only parse templates when notifications are enabled

* Use better description

.circleci/config.yml

@@ -2,29 +2,25 @@ version: 2.1
 
 jobs:
   canary:
-    docker:
-      - image: cimg/base:2020.06
+    machine:
+      image: ubuntu-2004:202201-02
     working_directory: ~/docker-volume-backup
     steps:
       - checkout
-      - setup_remote_docker:
-          version: 20.10.6
       - run:
           name: Build
           command: |
             docker build . -t offen/docker-volume-backup:canary
       - run:
-          name: Create container from image
+          name: Install gnupg
           command: |
-            docker run -d offen/docker-volume-backup:canary
-            echo "Sleeping for 30s before checking if container is still running."
-            sleep 30
-            count=$(docker ps -q | wc -l)
-            if [[ $count != "1" ]]; then
-              echo "Expected one container to be running, found $count."
-              exit 1
-            fi
-            docker stop $(docker ps -q)
+            sudo apt-get install -y gnupg
+      - run:
+          name: Run tests
+          working_directory: ~/docker-volume-backup/test
+          command: |
+            export GPG_TTY=$(tty)
+            ./test.sh canary
 
   build:
     docker:
@@ -48,10 +44,13 @@ jobs:
             docker context create docker-volume-backup
             docker buildx create docker-volume-backup --name docker-volume-backup --use
             docker buildx inspect --bootstrap
-            docker buildx build --platform linux/arm64,linux/amd64 \
-              -t offen/docker-volume-backup:$CIRCLE_TAG \
-              -t offen/docker-volume-backup:latest \
-              . --push
+            tag_args="-t offen/docker-volume-backup:$CIRCLE_TAG"
+            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"
+            fi
+            docker buildx build --platform linux/amd64,linux/arm64,linux/arm/v7 \
+               $tag_args . --push
 
 workflows:
   version: 2

.dockerignore

@@ -0,0 +1 @@
+test

.editorconfig

@@ -0,0 +1,18 @@
+# EditorConfig is awesome: http://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.go]
+indent_style = tab

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,20 @@
+* **I'm submitting a ...**
+  - [ ] bug report
+  - [ ] feature request
+  - [ ] support request
+
+* **What is the current behavior?**
+
+* **If the current behavior is a bug, please provide the configuration and steps to reproduce and if possible a minimal demo of the problem.**
+
+* **What is the expected behavior?**
+
+* **What is the motivation / use case for changing the behavior?**
+
+* **Please tell us about your environment:**
+  
+  - Image version:
+  - Docker version: 
+  - docker-compose version:
+
+* **Other information** (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, etc)

Dockerfile

@@ -1,21 +1,24 @@
 # Copyright 2021 - Offen Authors <hioffen@posteo.de>
-# SPDX-License-Identifier: MIT
+# SPDX-License-Identifier: MPL-2.0
 
-FROM alpine:3.14
+FROM golang:1.17-alpine as builder
+
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY cmd/backup ./cmd/backup/
+WORKDIR /app/cmd/backup
+RUN go build -o backup .
+
+FROM alpine:3.15
 
 WORKDIR /root
 
-RUN apk add --update ca-certificates docker openrc gnupg
-RUN update-ca-certificates
-RUN rc-update add docker boot
+RUN apk add --update ca-certificates
 
-ARG TARGETARCH=amd64
-RUN wget https://dl.min.io/client/mc/release/linux-$TARGETARCH/mc && \
-  chmod +x mc && \
-  mv mc /usr/bin/mc
+COPY --from=builder /app/cmd/backup/backup /usr/bin/backup
 
-COPY src/backup.sh src/entrypoint.sh /root/
-RUN chmod +x backup.sh && mv backup.sh /usr/bin/backup \
-  && chmod +x entrypoint.sh
+COPY ./entrypoint.sh /root/
+RUN chmod +x entrypoint.sh
 
 ENTRYPOINT ["/root/entrypoint.sh"]

NOTICE

@@ -1,22 +0,0 @@
-Copyright 2021 Offen Authors <hioffen@posteo.de>
-
-This project contains software that is Copyright (c) 2018 Futurice
-Licensed under the Terms of the MIT License:
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.

README.md

@@ -1,81 +1,57 @@
+<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 to any S3 compatible storage.
+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 sidecar container to an existing Docker setup. It handles recurring backups of Docker volumes to any S3 compatible storage and rotates away old backups if configured.
+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__, __any S3 or WebDAV 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__.
 
-## Configuration
+<!-- MarkdownTOC -->
 
-Backup targets, schedule and retention are configured in environment variables:
+- [Quickstart](#quickstart)
+  - [Recurring backups in a compose setup](#recurring-backups-in-a-compose-setup)
+  - [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)
+  - [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)
+  - [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)
+- [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 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)
+  - [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)
 
-```ini
-########### BACKUP SCHEDULE
+<!-- /MarkdownTOC -->
 
-# Backups run on the given cron schedule and use the filename defined in the
-# template expression.
+---
 
-BACKUP_CRON_EXPRESSION="0 2 * * *"
-BACKUP_FILENAME="offen-db-%Y-%m-%dT%H-%M-%S.tar.gz"
+Code and documentation for `v1` versions are found on [this branch][v1-branch].
 
-########### BACKUP STORAGE
+[v1-branch]: https://github.com/offen/docker-volume-backup/tree/v1
 
-# Define credentials for authenticating against the backup storage and a bucket
-# name. Although all of these values are `AWS`-prefixed, the setup can be used
-# with any S3 compatible storage.
+## Quickstart
 
-AWS_ACCESS_KEY_ID="<xxx>"
-AWS_SECRET_ACCESS_KEY="<xxx>"
-AWS_S3_BUCKET_NAME="<xxx>"
+### Recurring backups in a compose setup
 
-# This is the FQDN of your storage server, e.g. `storage.example.com`.
-# Do not set this when working against AWS S3.
-# AWS_ENDPOINT="<xxx>"
-
-########### BACKUP PRUNING
-
-# Define this value to enable automatic pruning of old backups. The value
-# declares the number of days for which a backup is kept.
-
-# BACKUP_RETENTION_DAYS="7"
-
-# In case the duration a backup takes fluctuates noticeably in your setup
-# you can adjust this setting to make sure there are no race conditions
-# between the backup finishing and the pruning not deleting backups that
-# sit on the very edge of the time window. Set this value to a duration
-# that is expected to be bigger than the maximum difference of backups.
-# Valid values have a suffix of (s)econds, (m)inutes, (h)ours, or (d)ays.
-
-# BACKUP_PRUNING_LEEWAY="10m"
-
-########### BACKUP ENCRYPTION
-
-# Backups can be encrypted using gpg in case a passphrase is given
-
-# GPG_PASSPHRASE="<xxx>"
-
-########### STOPPING CONTAINERS DURING BACKUP
-
-# Containers can be stopped by applying a
-# `docker-volume-backup.stop-during-backup` label. By default, all containers
-# that are labeled with `true` will be stopped. If you need more fine grained
-# control (e.g. when running multiple containers based on this image), you can
-# override this default by specifying a different value here.
-
-# BACKUP_STOP_CONTAINER_LABEL="service1"
-
-########### MINIO CLIENT CONFIGURATION
-
-# Pass these additional flags to all MinIO client `mc` invocations.
-# This can be used for example to pass `--insecure` when using self
-# signed certificates, or passing `--debug` to gain insights on
-# unexpected behavior.
-
-# MC_GLOBAL_OPTIONS="<xxx>"
-```
-
-## Example in a docker-compose setup
-
-Most likely, you will use this image as a sidecar container in an existing docker-compose setup like this:
+Add a `backup` service to your compose setup and mount the volumes you would like to see backed up:
 
 ```yml
 version: '3'
@@ -93,25 +69,723 @@ services:
       - docker-volume-backup.stop-during-backup=true
 
   backup:
+    # In production, it is advised to lock your image tag to a proper
+    # release version instead of using `latest`.
+    # Check https://github.com/offen/docker-volume-backup/releases
+    # for a list of available releases.
     image: offen/docker-volume-backup:latest
     restart: always
-    env_file: ./backup.env
+    env_file: ./backup.env # see below for configuration reference
     volumes:
+      - 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
-      - data:/backup/my-app-backup: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
+      # location inside of the container by setting `BACKUP_ARCHIVE`.
+      # You can omit this if you do not want to keep local backups.
+      - /path/to/local_backups:/archive
 volumes:
   data:
 ```
 
+### One-off backups using Docker CLI
+
+To run a one time backup, mount the volume you would like to see backed up into a container and run the `backup` command:
+
+```console
+docker run --rm \
+  -v data:/backup/data \
+  --env AWS_ACCESS_KEY_ID="<xxx>" \
+  --env AWS_SECRET_ACCESS_KEY="<xxx>" \
+  --env AWS_S3_BUCKET_NAME="<xxx>" \
+  --entrypoint backup \
+  offen/docker-volume-backup:latest
+```
+
+Alternatively, pass a `--env-file` in order to use a full config as described below.
+
+## Configuration reference
+
+Backup targets, schedule and retention are configured in environment variables.
+You can populate below template according to your requirements and use it as your `env_file`:
+
+```ini
+########### BACKUP SCHEDULE
+
+# Backups run on the given cron schedule in `busybox` flavor. If no
+# value is set, `@daily` will be used. If you do not want the cron
+# to ever run, use `0 0 5 31 2 ?`.
+
+# BACKUP_CRON_EXPRESSION="0 2 * * *"
+
+# The name of the backup file including the `.tar.gz` extension.
+# Format verbs will be replaced as in `strftime`. Omitting them
+# will result in the same filename for every backup run, which means previous
+# versions will be overwritten on subsequent runs. The default results
+# in filenames like `backup-2021-08-29T04-00-00.tar.gz`.
+
+# 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"
+
+# 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"
+
+########### BACKUP STORAGE
+
+# The name of the remote bucket that should be used for storing backups. If
+# this is not set, no remote backups will be stored.
+
+# 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.
+
+# AWS_ACCESS_KEY_ID="<xxx>"
+# AWS_SECRET_ACCESS_KEY="<xxx>"
+
+# 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
+# - ECS: http://169.254.170.2
+
+# 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
+# `s3.amazonaws.com`). If you need to set a specific (non-https) protocol, you
+# will need to use the option below.
+
+# AWS_ENDPOINT="storage.example.com"
+
+# The protocol to be used when communicating with your storage server.
+# Defaults to "https". You can set this to "http" when communicating with
+# a different Docker container on the same host for example.
+
+# 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. This can only be used
+# when AWS_ENDPOINT_PROTO is set to `https`.
+
+# AWS_ENDPOINT_INSECURE="true"
+
+# 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"
+
+# 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`
+# by default) when running the container. In case the specified directory does
+# not exist (nothing is mounted) in the container when the backup is running,
+# local backups will be skipped. Local paths are also be subject to pruning of
+# old backups as defined below.
+
+# BACKUP_ARCHIVE="/archive"
+
+########### BACKUP PRUNING
+
+# **IMPORTANT, PLEASE READ THIS BEFORE USING THIS FEATURE**:
+# The mechanism used for pruning old backups is not very sophisticated
+# and applies its rules to **all files in the target directory** by default,
+# which means that if you are storing your backups next to other files,
+# these might become subject to deletion too. When using this option
+# make sure the backup files are stored in a directory used exclusively
+# for such files, or to configure BACKUP_PRUNING_PREFIX to limit
+# removal to certain files.
+
+# Define this value to enable automatic rotation of old backups. The value
+# declares the number of days for which a backup is kept.
+
+# BACKUP_RETENTION_DAYS="7"
+
+# In case the duration a backup takes fluctuates noticeably in your setup
+# you can adjust this setting to make sure there are no race conditions
+# between the backup finishing and the rotation not deleting backups that
+# sit on the edge of the time window. Set this value to a duration
+# that is expected to be bigger than the maximum difference of backups.
+# Valid values have a suffix of (s)econds, (m)inutes or (h)ours. By default,
+# one minute is used.
+
+# BACKUP_PRUNING_LEEWAY="1m"
+
+# In case your target bucket or directory contains other files than the ones
+# managed by this container, you can limit the scope of rotation by setting
+# a prefix value. This would usually be the non-parametrized part of your
+# BACKUP_FILENAME. E.g. if BACKUP_FILENAME is `db-backup-%Y-%m-%dT%H-%M-%S.tar.gz`,
+# you can set BACKUP_PRUNING_PREFIX to `db-backup-` and make sure
+# unrelated files are not affected by the rotation mechanism.
+
+# BACKUP_PRUNING_PREFIX="backup-"
+
+########### BACKUP ENCRYPTION
+
+# Backups can be encrypted using gpg in case a passphrase is given.
+
+# GPG_PASSPHRASE="<xxx>"
+
+########### STOPPING CONTAINERS DURING BACKUP
+
+# Containers can be stopped by applying a
+# `docker-volume-backup.stop-during-backup` label. By default, all containers
+# that are labeled with `true` will be stopped. If you need more fine grained
+# control (e.g. when running multiple containers based on this image), you can
+# override this default by specifying a different value here.
+
+# BACKUP_STOP_CONTAINER_LABEL="service1"
+
+########### 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"
+
+########### 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
+# not set, no emails will be sent.
+
+# EMAIL_NOTIFICATION_RECIPIENT="you@example.com"
+
+# The "From" header of the sent email. Defaults to `noreply@nohost`.
+
+# EMAIL_NOTIFICATION_SENDER="no-reply@example.com"
+
+# Configuration and credentials for the SMTP server to be used.
+# EMAIL_SMTP_PORT defaults to 587.
+
+# EMAIL_SMTP_HOST="posteo.de"
+# EMAIL_SMTP_PASSWORD="<xxx>"
+# EMAIL_SMTP_USERNAME="no-reply@example.com"
+# EMAIL_SMTP_PORT="<port>"
+```
+
+In case you encouter double quoted values in your configuration you might be running an [older version of `docker-compose`].
+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
+
+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).
+By default, any container that is labeled `docker-volume-backup.stop-during-backup=true` will be stopped before the backup is being taken and restarted once it has finished.
+
+In case you need more fine grained control about which containers should be stopped (e.g. when backing up multiple volumes on different schedules), you can set the `BACKUP_STOP_CONTAINER_LABEL` environment variable and then use the same value for labeling:
+
+```yml
+version: '3'
+
+services:
+  app:
+    # definition for app ...
+    labels:
+      - docker-volume-backup.stop-during-backup=service1
+
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      BACKUP_STOP_CONTAINER_LABEL: service1
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Automatically pruning old backups
+
+When `BACKUP_RETENTION_DAYS` is configured, the image will check if there are any backups in the remote bucket or local archive that are older than the given retention value and rotate these backups away.
+
+Be aware that this mechanism looks at __all files in the target bucket or archive__, which means that other files that are older than the given deadline are deleted as well. In case you need to use a target that cannot be used exclusively for your backups, you can configure `BACKUP_PRUNING_PREFIX` to limit which files are considered eligible for deletion:
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
+      BACKUP_PRUNING_PREFIX: backup-
+      BACKUP_RETENTION_DAYS: 7
+    volumes:
+      - ${HOME}/backups:/archive
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Send email notifications on failed backup runs
+
+To send out email notifications on failed backup runs, provide SMTP credentials, a sender and a recipient:
+
+```yml
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      # ... other configuration values go here
+      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).
+
+### Encrypting your backup using GPG
+
+The image supports encrypting backups using GPG out of the box.
+In case a `GPG_PASSPHRASE` environment variable is set, the backup will be encrypted using the given key and saved as a `.gpg` file instead.
+
+Assuming you have `gpg` installed, you can decrypt such a backup using (your OS will prompt for the passphrase before decryption can happen):
+
+```console
+gpg -o backup.tar.gz -d backup.tar.gz.gpg
+```
+
+### Restoring a volume from a backup
+
+In case you need to restore a volume from a backup, the most straight forward procedure to do so would be:
+
+- Stop the container(s) that are using the volume
+- Untar the backup you want to restore
+  ```console
+  tar -C /tmp -xvf  backup.tar.gz
+  ```
+- 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 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
+
+Depending on your setup and the application(s) you are running, this might involve other steps to be taken still.
+
+### 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:latest
+    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.
+If you plan to have your containers / services stopped during backup, this means you need to apply the `on-failure` restart policy to your service's definitions.
+A restart policy of `always` is not compatible with this tool.
+
+---
+
+When running in Swarm mode, it's also advised to set a hard memory limit on your service (~25MB should be enough in most cases, but if you backup large files above half a gigabyte or similar, you might have to raise this in case the backup exits with `Killed`):
+
+```yml
+services:
+  backup:
+    image: offen/docker-volume-backup:latest
+    deployment:
+      resources:
+        limits:
+          memory: 25M
+```
+
+### Manually triggering a backup
+
+You can manually trigger a backup run outside of the defined cron schedule by executing the `backup` command inside the container:
+
+```
+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
+```
+
+## Recipes
+
+This section lists configuration for some real-world use cases that you can mix and match according to your needs.
+
+### Backing up to AWS S3
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
+      AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Backing up to Filebase
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_ENDPOINT: s3.filebase.com
+      AWS_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
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_ENDPOINT: minio.example.com
+      AWS_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: MINIOACCESSKEY
+      AWS_SECRET_ACCESS_KEY: MINIOSECRETKEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Backing up to WebDAV
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    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 locally
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    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
+      - ${HOME}/backups:/archive
+
+volumes:
+  data:
+```
+
+### Backing up to AWS S3 as well as locally
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
+      AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - ${HOME}/backups:/archive
+
+volumes:
+  data:
+```
+
+### Running on a custom cron schedule
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      # take a backup on every hour
+      BACKUP_CRON_EXPRESSION: "0 * * * *"
+      AWS_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
+      AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Rotating away backups that are older than 7 days
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_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
+      BACKUP_PRUNING_PREFIX: backup-
+      BACKUP_RETENTION_DAYS: 7
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Encrypting your backups using GPG
+
+```yml
+version: '3'
+
+services:
+  # ... define other services using the `data` volume here
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      AWS_BUCKET_NAME: backup-bucket
+      AWS_ACCESS_KEY_ID: AKIAIOSFODNN7EXAMPLE
+      AWS_SECRET_ACCESS_KEY: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
+      GPG_PASSPHRASE: somesecretstring
+    volumes:
+      - data:/backup/my-app-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data:
+```
+
+### Running multiple instances in the same setup
+
+```yml
+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
+    environment: &backup_environment
+      BACKUP_CRON_EXPRESSION: "0 2 * * *"
+      AWS_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`
+      BACKUP_STOP_CONTAINER_LABEL: service1
+    volumes:
+      - data_1:/backup/data-1-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+  backup_2:
+    <<: *backup_service
+    environment:
+      <<: *backup_environment
+      # Label the container using the `data_2` volume as `docker-volume-backup.stop-during-backup=service2`
+      BACKUP_CRON_EXPRESSION: "0 3 * * *"
+      BACKUP_STOP_CONTAINER_LABEL: service2
+    volumes:
+      - data_2:/backup/data-2-backup:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  data_1:
+  data_2:
+```
+
 ## 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`, making it very heavy. This version is roughly 1/3 in compressed size.
-- This image makes use of the MinIO client `mc` instead of the full blown AWS CLI for uploading backups.
-- The original image proposed to handle backup rotation through AWS S3 lifecycle policies. This image adds the option to rotate old backups through the same script so this functionality can also be offered for non-AWS storage backends like MinIO.
-- InfluxDB specific functionality was removed.
-- `arm64` Architecture is supported.
+- 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 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 failed backups are supported
+- IAM authentication through instance profiles is supported

cmd/backup/config.go

@@ -0,0 +1,42 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import "time"
+
+// Config holds all configuration values that are expected to be set
+// by users.
+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"`
+	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"`
+	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"`
+	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
+	AwsSecretAccessKey         string        `split_words:"true"`
+	AwsIamRoleEndpoint         string        `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"`
+	WebdavPath                 string        `split_words:"true" default:"/"`
+	WebdavUsername             string        `split_words:"true"`
+	WebdavPassword             string        `split_words:"true"`
+}

cmd/backup/hooks.go

@@ -0,0 +1,56 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+// 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 join(actionErrors...)
+	}
+	return nil
+}

cmd/backup/main.go

@@ -0,0 +1,57 @@
+// Copyright 2021-2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"os"
+)
+
+func main() {
+	unlock := lock("/var/lock/dockervolumebackup.lock")
+	defer unlock()
+
+	s, err := newScript()
+	if err != nil {
+		panic(err)
+	}
+
+	defer func() {
+		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(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 {
+		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()
+	}())
+
+	s.must(s.encryptBackup())
+	s.must(s.copyBackup())
+	s.must(s.pruneBackups())
+}

cmd/backup/notifications.go

@@ -0,0 +1,105 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"text/template"
+	"time"
+
+	sTypes "github.com/containrrr/shoutrrr/pkg/types"
+)
+
+//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("notifyFailure: error executing %s template: %w", titleTemplate, err)
+	}
+
+	bodyBuf := &bytes.Buffer{}
+	if err := s.template.ExecuteTemplate(bodyBuf, bodyTemplate, params); err != nil {
+		return fmt.Errorf("notifyFailure: error executing %s template: %w", bodyTemplate, err)
+	}
+
+	if err := s.sendNotification(titleBuf.String(), bodyBuf.String()); err != nil {
+		return fmt.Errorf("notifyFailure: 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", 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)
+	},
+}
+
+// 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 +1,666 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"text/template"
+	"time"
+
+	"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/m90/targz"
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+	"github.com/otiai10/copy"
+	"github.com/sirupsen/logrus"
+	"github.com/studio-b12/gowebdav"
+	"golang.org/x/crypto/openpgp"
+)
+
+// script holds all the stateful information required to orchestrate a
+// single backup run.
+type script struct {
+	cli          *client.Client
+	minioClient  *minio.Client
+	webdavClient *gowebdav.Client
+	logger       *logrus.Logger
+	sender       *router.ServiceRouter
+	template     *template.Template
+	hooks        []hook
+	hookLevel    hookLevel
+
+	file  string
+	stats *Stats
+
+	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:  StoragesStats{},
+		},
+	}
+
+	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
+	}
+
+	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")
+		}
+
+		options := minio.Options{
+			Creds:  creds,
+			Secure: s.c.AwsEndpointProto == "https",
+		}
+
+		if s.c.AwsEndpointInsecure {
+			if !options.Secure {
+				return nil, errors.New("newScript: AWS_ENDPOINT_INSECURE = true is only meaningful for https")
+			}
+
+			transport, err := minio.DefaultTransport(true)
+			if err != nil {
+				return nil, fmt.Errorf("newScript: failed to create default minio transport")
+			}
+			transport.TLSClientConfig.InsecureSkipVerify = true
+			options.Transport = transport
+		}
+
+		mc, err := minio.New(s.c.AwsEndpoint, &options)
+		if err != nil {
+			return nil, fmt.Errorf("newScript: error setting up minio client: %w", err)
+		}
+		s.minioClient = mc
+	}
+
+	if s.c.WebdavUrl != "" {
+		if s.c.WebdavUsername == "" || s.c.WebdavPassword == "" {
+			return nil, errors.New("newScript: WEBDAV_URL is defined, but no credentials were provided")
+		} else {
+			webdavClient := gowebdav.NewClient(s.c.WebdavUrl, s.c.WebdavUsername, s.c.WebdavPassword)
+			s.webdavClient = webdavClient
+		}
+	}
+
+	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("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...),
+		)
+	}
+
+	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("stopContainersAndRun: 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(
+				"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 {
+	backupSources := s.c.BackupSources
+
+	if s.c.BackupFromSnapshot {
+		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("takeBackup: 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("takeBackup: 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("takeBackup: error removing tar file: %w", err)
+		}
+		s.logger.Infof("Removed tar file `%s`.", tarFile)
+		return nil
+	})
+	if err := targz.Compress(backupSources, tarFile); err != nil {
+		return fmt.Errorf("takeBackup: error compressing backup folder: %w", err)
+	}
+
+	s.logger.Infof("Created backup of `%s` at `%s`.", backupSources, tarFile)
+	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
+	}
+
+	gpgFile := fmt.Sprintf("%s.gpg", s.file)
+	s.registerHook(hookLevelPlumbing, func(error) error {
+		if err := remove(gpgFile); err != nil {
+			return fmt.Errorf("encryptBackup: error removing gpg file: %w", err)
+		}
+		s.logger.Infof("Removed GPG file `%s`.", gpgFile)
+		return nil
+	})
+
+	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 stat, err := os.Stat(s.file); err != nil {
+		return fmt.Errorf("copyBackup: unable to stat backup file: %w", err)
+	} else {
+		size := stat.Size()
+		s.stats.BackupFile = BackupFileStats{
+			Size:     uint64(size),
+			Name:     name,
+			FullPath: s.file,
+		}
+	}
+
+	if s.minioClient != nil {
+		if _, err := s.minioClient.FPutObject(context.Background(), s.c.AwsS3BucketName, filepath.Join(s.c.AwsS3Path, name), s.file, minio.PutObjectOptions{
+			ContentType: "application/tar+gzip",
+		}); 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 s.webdavClient != nil {
+		bytes, err := os.ReadFile(s.file)
+		if err != nil {
+			return fmt.Errorf("copyBackup: error reading the file to be uploaded: %w", err)
+		}
+		if err := s.webdavClient.MkdirAll(s.c.WebdavPath, 0644); err != nil {
+			return fmt.Errorf("copyBackup: error creating directory '%s' on WebDAV server: %w", s.c.WebdavPath, err)
+		}
+		if err := s.webdavClient.Write(filepath.Join(s.c.WebdavPath, name), bytes, 0644); err != nil {
+			return fmt.Errorf("copyBackup: error uploading the file to WebDAV server: %w", err)
+		}
+		s.logger.Infof("Uploaded a copy of backup `%s` to WebDAV-URL '%s' at path '%s'.", s.file, s.c.WebdavUrl, s.c.WebdavPath)
+	}
+
+	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
+		if err := copyFile(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)
+		if s.c.BackupLatestSymlink != "" {
+			symlink := path.Join(s.c.BackupArchive, s.c.BackupLatestSymlink)
+			if _, err := os.Lstat(symlink); err == nil {
+				os.Remove(symlink)
+			}
+			if err := os.Symlink(name, symlink); err != nil {
+				return fmt.Errorf("copyBackup: error creating latest symlink: %w", err)
+			}
+			s.logger.Infof("Created/Updated symlink `%s` for latest backup.", s.c.BackupLatestSymlink)
+		}
+	}
+	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)
+
+	// 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.
+	var doPrune = func(lenMatches, lenCandidates int, description string, doRemoveFiles func() error) error {
+		if lenMatches != 0 && lenMatches != lenCandidates {
+			if err := doRemoveFiles(); err != nil {
+				return err
+			}
+			s.logger.Infof(
+				"Pruned %d out of %d %s as their age exceeded the configured retention period of %d days.",
+				lenMatches,
+				lenCandidates,
+				description,
+				s.c.BackupRetentionDays,
+			)
+		} else if lenMatches != 0 && lenMatches == lenCandidates {
+			s.logger.Warnf("The current configuration would delete all %d existing %s.", lenMatches, description)
+			s.logger.Warn("Refusing to do so, please check your configuration.")
+		} else {
+			s.logger.Infof("None of %d existing %s were pruned.", lenCandidates, description)
+		}
+		return nil
+	}
+
+	if s.minioClient != nil {
+		candidates := s.minioClient.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(
+					"pruneBackups: error looking up candidates from remote storage: %w",
+					candidate.Err,
+				)
+			}
+			if candidate.LastModified.Before(deadline) {
+				matches = append(matches, candidate)
+			}
+		}
+
+		s.stats.Storages.S3 = StorageStats{
+			Total:  uint(lenCandidates),
+			Pruned: uint(len(matches)),
+		}
+
+		doPrune(len(matches), lenCandidates, "remote backup(s)", func() error {
+			objectsCh := make(chan minio.ObjectInfo)
+			go func() {
+				for _, match := range matches {
+					objectsCh <- match
+				}
+				close(objectsCh)
+			}()
+			errChan := s.minioClient.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 join(removeErrors...)
+			}
+			return nil
+		})
+	}
+
+	if s.webdavClient != nil {
+		candidates, err := s.webdavClient.ReadDir(s.c.WebdavPath)
+		if err != nil {
+			return fmt.Errorf("pruneBackups: error looking up candidates from remote storage: %w", err)
+		}
+		var matches []fs.FileInfo
+		var lenCandidates int
+		for _, candidate := range candidates {
+			lenCandidates++
+			if candidate.ModTime().Before(deadline) {
+				matches = append(matches, candidate)
+			}
+		}
+
+		s.stats.Storages.WebDAV = StorageStats{
+			Total:  uint(lenCandidates),
+			Pruned: uint(len(matches)),
+		}
+
+		doPrune(len(matches), lenCandidates, "WebDAV backup(s)", func() error {
+			for _, match := range matches {
+				if err := s.webdavClient.Remove(filepath.Join(s.c.WebdavPath, match.Name())); err != nil {
+					return fmt.Errorf("pruneBackups: error removing file from WebDAV storage: %w", err)
+				}
+			}
+			return nil
+		})
+	}
+
+	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
+		globPattern := path.Join(
+			s.c.BackupArchive,
+			fmt.Sprintf("%s*", s.c.BackupPruningPrefix),
+		)
+		globMatches, err := filepath.Glob(globPattern)
+		if err != nil {
+			return fmt.Errorf(
+				"pruneBackups: 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 fmt.Errorf(
+					"pruneBackups: 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 fmt.Errorf(
+					"pruneBackups: error calling stat on file %s: %w",
+					candidate,
+					err,
+				)
+			}
+			if fi.ModTime().Before(deadline) {
+				matches = append(matches, candidate)
+			}
+		}
+
+		s.stats.Storages.Local = StorageStats{
+			Total:  uint(len(candidates)),
+			Pruned: uint(len(matches)),
+		}
+
+		doPrune(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(
+					"pruneBackups: %d error(s) deleting local files, starting with: %w",
+					len(removeErrors),
+					join(removeErrors...),
+				)
+			}
+			return nil
+		})
+	}
+	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 +1,49 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	"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
+}
+
+// StoragesStats stats about each possible archival location (Local, WebDAV, S3)
+type StoragesStats struct {
+	Local  StorageStats
+	WebDAV StorageStats
+	S3     StorageStats
+}
+
+// Stats global stats regarding script execution
+type Stats struct {
+	StartTime  time.Time
+	EndTime    time.Time
+	TookTime   time.Duration
+	LogOutput  *bytes.Buffer
+	Containers ContainersStats
+	BackupFile BackupFileStats
+	Storages   StoragesStats
+}

cmd/backup/util.go

@@ -0,0 +1,107 @@
+// Copyright 2022 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/gofrs/flock"
+)
+
+var noop = func() error { return nil }
+
+// 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 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()
+}
+
+// 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, ", ") + "]")
+}
+
+// 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: error writing to buffer: %w", err)
+	}
+	return b.writer.Write(p)
+}

docs/NOTIFICATION-TEMPLATES.md

@@ -0,0 +1,38 @@
+# 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`)
+  * `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` or `WebDAV`:
+      * `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 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`)

entrypoint.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+# Copyright 2021 - Offen Authors <hioffen@posteo.de>
+# SPDX-License-Identifier: MPL-2.0
+
+set -e
+
+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 "Starting cron in foreground."
+crond -f -l 8

go.mod

@@ -0,0 +1,59 @@
+module github.com/offen/docker-volume-backup
+
+go 1.17
+
+require (
+	github.com/containrrr/shoutrrr v0.5.2
+	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 v0.0.0-20220208141135-d3baeef59a97
+	github.com/minio/minio-go/v7 v7.0.16
+	github.com/otiai10/copy v1.7.0
+	github.com/sirupsen/logrus v1.8.1
+	github.com/studio-b12/gowebdav v0.0.0-20211109083228-3f8721cd4b6f
+	golang.org/x/crypto v0.0.0-20210817164053-32db794688a5
+)
+
+require (
+	github.com/Microsoft/go-winio v0.4.17 // indirect
+	github.com/containerd/containerd v1.5.5 // 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/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 v1.3.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.13.6 // indirect
+	github.com/klauspost/cpuid/v2 v2.0.9 // 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/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/morikuni/aec v1.0.0 // 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/pkg/errors v0.9.1 // indirect
+	github.com/rs/xid v1.3.0 // 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 v0.3.6 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // 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/ini.v1 v1.65.0 // indirect
+	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+)

src/backup.sh

@@ -1,96 +0,0 @@
-#!/bin/sh
-
-# Copyright 2021 - Offen Authors <hioffen@posteo.de>
-# SPDX-License-Identifier: MPL-2.0
-
-# Portions of this file are taken from github.com/futurice/docker-volume-backup
-# See NOTICE for information about authors and licensing.
-
-source env.sh
-
-function info {
-  echo -e "\n[INFO] $1\n"
-}
-
-info "Preparing backup"
-DOCKER_SOCK="/var/run/docker.sock"
-
-if [ -S "$DOCKER_SOCK" ]; then
-  TEMPFILE="$(mktemp)"
-  docker ps \
-    --format "{{.ID}}" \
-    --filter "label=docker-volume-backup.stop-during-backup=$BACKUP_STOP_CONTAINER_LABEL" \
-    > "$TEMPFILE"
-  CONTAINERS_TO_STOP="$(cat $TEMPFILE | tr '\n' ' ')"
-  CONTAINERS_TO_STOP_TOTAL="$(cat $TEMPFILE | wc -l)"
-  CONTAINERS_TOTAL="$(docker ps --format "{{.ID}}" | wc -l)"
-  rm "$TEMPFILE"
-  echo "$CONTAINERS_TOTAL containers running on host in total."
-  echo "$CONTAINERS_TO_STOP_TOTAL containers marked to be stopped during backup."
-else
-  CONTAINERS_TO_STOP_TOTAL="0"
-  CONTAINERS_TOTAL="0"
-  echo "Cannot access \"$DOCKER_SOCK\", won't look for containers to stop."
-fi
-
-if [ "$CONTAINERS_TO_STOP_TOTAL" != "0" ]; then
-  info "Stopping containers"
-  docker stop $CONTAINERS_TO_STOP
-fi
-
-info "Creating backup"
-BACKUP_FILENAME="$(date +"${BACKUP_FILENAME:-backup-%Y-%m-%dT%H-%M-%S.tar.gz}")"
-tar -czvf "$BACKUP_FILENAME" $BACKUP_SOURCES # allow the var to expand, in case we have multiple sources
-
-if [ ! -z "$GPG_PASSPHRASE" ]; then
-  info "Encrypting backup"
-  gpg --symmetric --cipher-algo aes256 --batch --passphrase "$GPG_PASSPHRASE" \
-    -o "${BACKUP_FILENAME}.gpg" $BACKUP_FILENAME
-  rm $BACKUP_FILENAME
-  BACKUP_FILENAME="${BACKUP_FILENAME}.gpg"
-fi
-
-if [ "$CONTAINERS_TO_STOP_TOTAL" != "0" ]; then
-  info "Starting containers back up"
-  docker start $CONTAINERS_TO_STOP
-fi
-
-if [ ! -z "$AWS_S3_BUCKET_NAME" ]; then
-  info "Uploading backup to remote storage"
-  echo "Will upload to bucket \"$AWS_S3_BUCKET_NAME\"."
-  mc cp $MC_GLOBAL_OPTIONS "$BACKUP_FILENAME" "backup-target/$AWS_S3_BUCKET_NAME"
-  echo "Upload finished."
-fi
-
-if [ -f "$BACKUP_FILENAME" ]; then
-  info "Cleaning up"
-  rm -vf "$BACKUP_FILENAME"
-fi
-
-info "Backup finished"
-echo "Will wait for next scheduled backup."
-
-if [ ! -z "$BACKUP_RETENTION_DAYS" ]; then
-  info "Pruning old backups"
-  echo "Sleeping ${BACKUP_PRUNING_LEEWAY} before checking eligibility."
-  sleep "$BACKUP_PRUNING_LEEWAY"
-  bucket=$AWS_S3_BUCKET_NAME
-
-  rule_applies_to=$(mc rm $MC_GLOBAL_OPTIONS --fake --recursive -force --older-than "${BACKUP_RETENTION_DAYS}d" "backup-target/$bucket" | wc -l)
-  if [ "$rule_applies_to" == "0" ]; then
-    echo "No backups found older than the configured retention period of $BACKUP_RETENTION_DAYS days."
-    echo "Doing nothing."
-    exit 0
-  fi
-
-  total=$(mc ls $MC_GLOBAL_OPTIONS "backup-target/$bucket" | wc -l)
-
-  if [ "$rule_applies_to" == "$total" ]; then
-    echo "Using a retention of ${BACKUP_RETENTION_DAYS} days would prune all currently existing backups, will not continue."
-    echo "If this is what you want, please remove files manually instead of using this script."
-    exit 1
-  fi
-
-  mc rm $MC_GLOBAL_OPTIONS --recursive -force --older-than "${BACKUP_RETENTION_DAYS}d" "backup-target/$bucket"
-  echo "Successfully pruned ${rule_applies_to} backups older than ${BACKUP_RETENTION_DAYS} days."
-fi

src/entrypoint.sh

@@ -1,40 +0,0 @@
-#!/bin/sh
-
-# Copyright 2021 - Offen Authors <hioffen@posteo.de>
-# SPDX-License-Identifier: MPL-2.0
-
-# Portions of this file are taken from github.com/futurice/docker-volume-backup
-# See NOTICE for information about authors and licensing.
-
-set -e
-
-# Write cronjob env to file, fill in sensible defaults, and read them back in
-cat <<EOF > env.sh
-BACKUP_SOURCES="${BACKUP_SOURCES:-/backup}"
-BACKUP_CRON_EXPRESSION="${BACKUP_CRON_EXPRESSION:-@daily}"
-BACKUP_FILENAME=${BACKUP_FILENAME:-"backup-%Y-%m-%dT%H-%M-%S.tar.gz"}
-
-BACKUP_RETENTION_DAYS="${BACKUP_RETENTION_DAYS:-}"
-BACKUP_PRUNING_LEEWAY="${BACKUP_PRUNING_LEEWAY:-10m}"
-
-AWS_S3_BUCKET_NAME="${AWS_S3_BUCKET_NAME:-}"
-AWS_ENDPOINT="${AWS_ENDPOINT:-s3.amazonaws.com}"
-
-GPG_PASSPHRASE="${GPG_PASSPHRASE:-}"
-
-BACKUP_STOP_CONTAINER_LABEL="${BACKUP_STOP_CONTAINER_LABEL:-true}"
-
-MC_GLOBAL_OPTIONS="${MC_GLOBAL_OPTIONS:-}"
-EOF
-chmod a+x env.sh
-source env.sh
-
-mc $MC_GLOBAL_OPTIONS alias set backup-target "https://$AWS_ENDPOINT" "$AWS_ACCESS_KEY_ID" "$AWS_SECRET_ACCESS_KEY"
-
-# Add our cron entry, and direct stdout & stderr to Docker commands stdout
-echo "Installing cron.d entry with expression $BACKUP_CRON_EXPRESSION."
-echo "$BACKUP_CRON_EXPRESSION backup 2>&1" | crontab -
-
-# Let cron take the wheel
-echo "Starting cron in foreground."
-crond -f -l 8

test/cli/run.sh

@@ -0,0 +1,67 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+docker network create test_network
+docker volume create backup_data
+docker volume create app_data
+# This volume is created to test whether empty directories are handled
+# correctly. It is not supposed to hold any data.
+docker volume create empty_data
+
+docker run -d \
+  --name minio \
+  --network test_network \
+  --env MINIO_ROOT_USER=test \
+  --env MINIO_ROOT_PASSWORD=test \
+  --env MINIO_ACCESS_KEY=test \
+  --env MINIO_SECRET_KEY=GMusLtUmILge2by+z890kQ \
+  -v backup_data:/data \
+  minio/minio:RELEASE.2020-08-04T23-10-51Z server /data
+
+docker exec minio mkdir -p /data/backup
+
+docker run -d \
+  --name offen \
+  --network test_network \
+  -v app_data:/var/opt/offen/ \
+  offen/offen:latest
+
+sleep 10
+
+docker run --rm \
+  --network test_network \
+  -v app_data:/backup/app_data \
+  -v empty_data:/backup/empty_data \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  --env AWS_ACCESS_KEY_ID=test \
+  --env AWS_SECRET_ACCESS_KEY=GMusLtUmILge2by+z890kQ \
+  --env AWS_ENDPOINT=minio:9000 \
+  --env AWS_ENDPOINT_PROTO=http \
+  --env AWS_S3_BUCKET_NAME=backup \
+  --env BACKUP_FILENAME=test.tar.gz \
+  --env "BACKUP_FROM_SNAPSHOT=true" \
+  --entrypoint backup \
+  offen/docker-volume-backup:$TEST_VERSION
+
+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 && test -d /backup/empty_data'
+
+echo "[TEST:PASS] Found relevant files in untared remote backup."
+
+# This test does not stop containers during backup. This is happening on
+# purpose in order to cover this setup as well.
+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
+
+echo "[TEST:PASS] All containers running post backup."
+
+docker rm $(docker stop minio offen)
+docker volume rm backup_data app_data
+docker network rm test_network

test/compose/.gitignore

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

test/compose/docker-compose.yml

@@ -0,0 +1,64 @@
+version: '3'
+
+services:
+  minio:
+    image: minio/minio:RELEASE.2020-08-04T23-10-51Z
+    environment:
+      MINIO_ROOT_USER: test
+      MINIO_ROOT_PASSWORD: test
+      MINIO_ACCESS_KEY: test
+      MINIO_SECRET_KEY: GMusLtUmILge2by+z890kQ
+    entrypoint: /bin/ash -c 'mkdir -p /data/backup && minio server /data'
+    volumes:
+      - minio_backup_data:/data
+
+  webdav:
+    image: bytemark/webdav:2.4
+    environment:
+      AUTH_TYPE: Digest
+      USERNAME: test
+      PASSWORD: test
+    volumes:
+      - webdav_backup_data:/var/lib/dav
+
+  backup: &default_backup_service
+    image: offen/docker-volume-backup:${TEST_VERSION}
+    hostname: hostnametoken
+    depends_on:
+      - minio
+      - webdav
+    restart: always
+    environment:
+      AWS_ACCESS_KEY_ID: test
+      AWS_SECRET_ACCESS_KEY: GMusLtUmILge2by+z890kQ
+      AWS_ENDPOINT: minio:9000
+      AWS_ENDPOINT_PROTO: http
+      AWS_S3_BUCKET_NAME: backup
+      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
+      GPG_PASSPHRASE: 1234secret
+      WEBDAV_URL: http://webdav/
+      WEBDAV_PATH: /my/new/path/
+      WEBDAV_USERNAME: test
+      WEBDAV_PASSWORD: test
+    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:
+  minio_backup_data:
+  webdav_backup_data:
+  app_data:

test/compose/run.sh

@@ -0,0 +1,68 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+# A symlink for a known file in the volume is created so the test can check
+# whether symlinks are preserved on backup.
+docker-compose exec offen ln -s /var/opt/offen/offen.db /var/opt/offen/db.link
+docker-compose exec backup backup
+
+sleep 5
+if [ "$(docker-compose ps -q | wc -l)" != "4" ]; 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."
+
+
+docker run --rm -it \
+  -v compose_minio_backup_data:/minio_data \
+  -v compose_webdav_backup_data:/webdav_data alpine \
+  ash -c 'apk add gnupg && \
+          echo 1234secret | gpg -d --pinentry-mode loopback --passphrase-fd 0 --yes /minio_data/backup/test-hostnametoken.tar.gz.gpg > /tmp/test-hostnametoken.tar.gz && tar -xf /tmp/test-hostnametoken.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db && \
+          echo 1234secret | gpg -d --pinentry-mode loopback --passphrase-fd 0 --yes /webdav_data/data/my/new/path/test-hostnametoken.tar.gz.gpg > /tmp/test-hostnametoken.tar.gz && tar -xf /tmp/test-hostnametoken.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
+
+echo "[TEST:PASS] Found relevant files in decrypted and untared remote backups."
+
+echo 1234secret | gpg -d --pinentry-mode loopback --yes --passphrase-fd 0 ./local/test-hostnametoken.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 decrypted and untared local backup."
+
+test -L ./local/test-hostnametoken.latest.tar.gz.gpg
+echo "[TEST: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
+
+docker run --rm -it \
+  -v compose_minio_backup_data:/minio_data \
+  -v compose_webdav_backup_data:/webdav_data alpine \
+  ash -c '[ $(find /minio_data/backup/ -type f | wc -l) = "1" ] && \
+          [ $(find /webdav_data/data/my/new/path/ -type f | wc -l) = "1" ]'
+
+echo "[TEST:PASS] Remote backups have not been deleted."
+
+if [ "$(find ./local -type f | wc -l)" != "1" ]; then
+  echo "[TEST:FAIL] Backups should not have been deleted, instead seen:"
+  find ./local -type f
+  exit 1
+fi
+echo "[TEST: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 +1,36 @@
+version: '3'
+
+services:
+  backup: &default_backup_service
+    image: offen/docker-volume-backup:${TEST_VERSION}
+    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}
+    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, yay!
+{{- end }}
+
+{{ define "body_success" -}}
+Backing up {{ .Stats.BackupFile.FullPath }} succeeded.
+{{- end }}

test/notifications/run.sh

@@ -0,0 +1,52 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+GOTIFY_TOKEN=$(curl -sSLX POST -H 'Content-Type: application/json' -d '{"name":"test"}' http://admin:custom@localhost:8080/application | jq -r '.token')
+echo "[TEST: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 [ "$NUM_MESSAGES" != 0 ]; then
+  echo "[TEST:FAIL] Expected no notifications to be sent when not configured"
+  exit 1
+fi
+echo "[TEST:PASS] No notifications were sent when not configured."
+
+docker-compose down
+
+NOTIFICATION_URLS="gotify://gotify/${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
+  echo "[TEST:FAIL] Expected one notifications to be sent when configured"
+  exit 1
+fi
+echo "[TEST: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, yay!" ]; then
+  echo "[TEST:FAIL] Unexpected notification title $MESSAGE_TITLE"
+  exit 1
+fi
+echo "[TEST:PASS] Custom notification title was used."
+
+if [ "$MESSAGE_BODY" != "Backing up /tmp/test.tar.gz succeeded." ]; then
+  echo "[TEST:FAIL] Unexpected notification body $MESSAGE_BODY"
+  exit 1
+fi
+echo "[TEST:PASS] Custom notification body was used."
+
+docker-compose down --volumes

test/swarm/docker-compose.yml

@@ -0,0 +1,65 @@
+# Copyright 2020-2021 - Offen Authors <hioffen@posteo.de>
+# SPDX-License-Identifier: Unlicense
+
+version: '3.8'
+
+services:
+  minio:
+    image: minio/minio:RELEASE.2020-08-04T23-10-51Z
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      MINIO_ROOT_USER: test
+      MINIO_ROOT_PASSWORD: test
+      MINIO_ACCESS_KEY: test
+      MINIO_SECRET_KEY: GMusLtUmILge2by+z890kQ
+    entrypoint: /bin/ash -c 'mkdir -p /data/backup && minio server /data'
+    volumes:
+      - backup_data:/data
+
+  backup: &default_backup_service
+    image: offen/docker-volume-backup:${TEST_VERSION}
+    depends_on:
+      - minio
+    deploy:
+      restart_policy:
+        condition: on-failure
+    environment:
+      AWS_ACCESS_KEY_ID: test
+      AWS_SECRET_ACCESS_KEY: GMusLtUmILge2by+z890kQ
+      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
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup=true
+    deploy:
+      replicas: 2
+      restart_policy:
+        condition: on-failure
+
+  pg:
+    image: postgres:12.2-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:
+  pg_data:

test/swarm/run.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+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."
+  sleep 1
+done
+
+sleep 20
+
+docker exec $(docker ps -q -f name=backup) backup
+
+docker run --rm -it \
+  -v test_stack_backup_data:/data alpine \
+  ash -c 'tar -xf /data/backup/test.tar.gz && test -f /backup/pg_data/PG_VERSION'
+
+echo "[TEST:PASS] Found relevant files in untared backup."
+
+sleep 5
+if [ "$(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."
+
+docker stack rm test_stack
+docker swarm leave --force

test/test.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+set -e
+
+TEST_VERSION=${1:-canary}
+
+for dir in $(ls -d -- */); do
+  test="${dir}run.sh"
+  echo "################################################"
+  echo "Now running $test"
+  echo "################################################"
+  echo ""
+  TEST_VERSION=$TEST_VERSION /bin/sh $test
+  echo ""
+  echo "$test passed"
+  echo ""
+done