update github.com/otai/copy, use PreserveOwner option

* reuse hook mechanism for scheduling clean up tasks

* register hooks before creating files or dirs

* fix logging order

* use typed hook levels

.circleci/config.yml

@@ -2,29 +2,24 @@ version: 2.1
 
 jobs:
   canary:
-    docker:
-      - image: cimg/base:2020.06
+    machine:
+      image: ubuntu-1604:202007-01
     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: |
+            ./test.sh canary
 
   build:
     docker:
@@ -48,10 +43,13 @@ 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

Dockerfile

@@ -1,21 +1,23 @@
 # Copyright 2021 - Offen Authors <hioffen@posteo.de>
-# SPDX-License-Identifier: MIT
+# SPDX-License-Identifier: MPL-2.0
+
+FROM golang:1.17-alpine as builder
+
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY cmd/backup/main.go ./cmd/backup/main.go
+RUN go build -o backup cmd/backup/main.go
 
 FROM alpine:3.14
 
 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/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 +1,49 @@
 # 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__ or __any S3 compatible storage__ (or both), and __rotates away old backups__ if configured. It also supports __encrypting your backups using GPG__ and __sending notifications for failed backup runs__.
 
-## 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)
+  - [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)
+- [Recipes](#recipes)
+  - [Backing up to AWS S3](#backing-up-to-aws-s3)
+  - [Backing up to MinIO](#backing-up-to-minio)
+  - [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 +61,567 @@ 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
       - /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"
+
+# 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"
+
+# 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"
+
+# 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"
+
+########### EMAIL NOTIFICATIONS ON FAILED BACKUP RUNS
+
+# In case SMTP credentials are provided, notification emails can be sent out on
+# failed backup runs. These emails will contain the start time, the error
+# message and all log output prior to the failure.
+
+# 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>"
+```
+
+## 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
+      EMAIL_SMTP_HOST: "smtp.example.com"
+      EMAIL_SMTP_PASSWORD: "password"
+      EMAIL_SMTP_USERNAME: "username"
+      EMAIL_NOTIFICATION_SENDER: "noreply@example.com"
+      EMAIL_NOTIFICATION_RECIPIENT: "notifications@example.com"
+```
+
+### 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 one-off container, mount the volume (the example assumes it's named `data`) and copy over the backup. Make sure you copy the correct path level (this depends on how you mount your volume into the backup container), you might need to strip some leading elements
+  ```console
+  docker run -d --name backup_restore -v data:/backup_restore alpine
+  docker cp /tmp/backup/data-backup backup_restore:/backup_restore
+  docker stop backup_restore
+  docker rm backup_restore
+  ```
+- 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
+```
+
+## 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 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 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/main.go

@@ -0,0 +1,749 @@
+// Copyright 2021 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/filters"
+	"github.com/docker/docker/api/types/swarm"
+	"github.com/docker/docker/client"
+	"github.com/go-gomail/gomail"
+	"github.com/gofrs/flock"
+	"github.com/kelseyhightower/envconfig"
+	"github.com/leekchan/timeutil"
+	"github.com/m90/targz"
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+	"github.com/otiai10/copy"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/crypto/openpgp"
+)
+
+func main() {
+	unlock := lock("/var/lock/dockervolumebackup.lock")
+	defer unlock()
+
+	s, err := newScript()
+	if err != nil {
+		panic(err)
+	}
+
+	defer func() {
+		if pArg := recover(); pArg != nil {
+			if err, ok := pArg.(error); ok {
+				if hookErr := s.runHooks(err, hookLevelCleanup, hookLevelFailure); hookErr != nil {
+					s.logger.Errorf("An error occurred calling the registered hooks: %s", hookErr)
+				}
+				os.Exit(1)
+			}
+			panic(pArg)
+		}
+
+		if err := s.runHooks(nil, hookLevelCleanup); 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.pruneOldBackups())
+}
+
+// script holds all the stateful information required to orchestrate a
+// single backup run.
+type script struct {
+	cli    *client.Client
+	mc     *minio.Client
+	logger *logrus.Logger
+	hooks  []hook
+
+	start  time.Time
+	file   string
+	output *bytes.Buffer
+
+	c *config
+}
+
+type config struct {
+	BackupSources              string        `split_words:"true" default:"/backup"`
+	BackupFilename             string        `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.tar.gz"`
+	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"`
+	AwsEndpoint                string        `split_words:"true" default:"s3.amazonaws.com"`
+	AwsEndpointProto           string        `split_words:"true" default:"https"`
+	AwsEndpointInsecure        bool          `split_words:"true"`
+	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
+	AwsSecretAccessKey         string        `split_words:"true"`
+	AwsIamRoleEndpoint         string        `split_words:"true"`
+	GpgPassphrase              string        `split_words:"true"`
+	EmailNotificationRecipient string        `split_words:"true"`
+	EmailNotificationSender    string        `split_words:"true" default:"noreply@nohost"`
+	EmailSMTPHost              string        `envconfig:"EMAIL_SMTP_HOST"`
+	EmailSMTPPort              int           `envconfig:"EMAIL_SMTP_PORT" default:"587"`
+	EmailSMTPUsername          string        `envconfig:"EMAIL_SMTP_USERNAME"`
+	EmailSMTPPassword          string        `envconfig:"EMAIL_SMTP_PASSWORD"`
+}
+
+var msgBackupFailed = "backup run failed"
+
+// newScript creates all resources needed for the script to perform actions against
+// remote resources like the Docker engine or remote storage locations. All
+// reading from env vars or other configuration sources is expected to happen
+// in this method.
+func newScript() (*script, error) {
+	stdOut, logBuffer := buffer(os.Stdout)
+	s := &script{
+		c: &config{},
+		logger: &logrus.Logger{
+			Out:       stdOut,
+			Formatter: new(logrus.TextFormatter),
+			Hooks:     make(logrus.LevelHooks),
+			Level:     logrus.InfoLevel,
+		},
+		start:  time.Now(),
+		output: logBuffer,
+	}
+
+	if err := envconfig.Process("", s.c); err != nil {
+		return nil, fmt.Errorf("newScript: failed to process configuration values: %w", err)
+	}
+
+	s.file = path.Join("/tmp", s.c.BackupFilename)
+
+	_, err := os.Stat("/var/run/docker.sock")
+	if !os.IsNotExist(err) {
+		cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
+		if err != nil {
+			return nil, fmt.Errorf("newScript: failed to create docker client")
+		}
+		s.cli = cli
+	}
+
+	if s.c.AwsS3BucketName != "" {
+		var creds *credentials.Credentials
+		if s.c.AwsAccessKeyID != "" && s.c.AwsSecretAccessKey != "" {
+			creds = credentials.NewStaticV4(
+				s.c.AwsAccessKeyID,
+				s.c.AwsSecretAccessKey,
+				"",
+			)
+		} else if s.c.AwsIamRoleEndpoint != "" {
+			creds = credentials.NewIAM(s.c.AwsIamRoleEndpoint)
+		} else {
+			return nil, errors.New("newScript: AWS_S3_BUCKET_NAME is defined, but no credentials were provided")
+		}
+
+		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.mc = mc
+	}
+
+	if s.c.EmailNotificationRecipient != "" {
+		s.hooks = append(s.hooks, hook{hookLevelFailure, func(err error, start time.Time, logOutput string) error {
+			mailer := gomail.NewDialer(
+				s.c.EmailSMTPHost, s.c.EmailSMTPPort, s.c.EmailSMTPUsername, s.c.EmailSMTPPassword,
+			)
+
+			subject := fmt.Sprintf(
+				"Failure running docker-volume-backup at %s", start.Format(time.RFC3339),
+			)
+			body := fmt.Sprintf(
+				"Running docker-volume-backup failed with error: %s\n\nLog output of the failed run was:\n\n%s\n", err, logOutput,
+			)
+
+			message := gomail.NewMessage()
+			message.SetHeader("From", s.c.EmailNotificationSender)
+			message.SetHeader("To", s.c.EmailNotificationRecipient)
+			message.SetHeader("Subject", subject)
+			message.SetBody("text/plain", body)
+			return mailer.DialAndSend(message)
+		}})
+	}
+
+	return s, nil
+}
+
+var noop = func() error { return nil }
+
+// registerHook adds the given action at the given level.
+func (s *script) registerHook(level hookLevel, action func(err error, start time.Time, logOutput string) error) {
+	s.hooks = append(s.hooks, hook{level, action})
+}
+
+// stopContainers stops all Docker containers that are marked as to being
+// stopped during the backup and returns a function that can be called to
+// restart everything that has been stopped.
+func (s *script) stopContainers() (func() error, error) {
+	if s.cli == nil {
+		return noop, nil
+	}
+
+	allContainers, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+		Quiet: true,
+	})
+	if err != nil {
+		return noop, fmt.Errorf("stopContainersAndRun: error querying for containers: %w", err)
+	}
+
+	containerLabel := fmt.Sprintf(
+		"docker-volume-backup.stop-during-backup=%s",
+		s.c.BackupStopContainerLabel,
+	)
+	containersToStop, err := s.cli.ContainerList(context.Background(), types.ContainerListOptions{
+		Quiet: true,
+		Filters: filters.NewArgs(filters.KeyValuePair{
+			Key:   "label",
+			Value: containerLabel,
+		}),
+	})
+
+	if err != nil {
+		return noop, fmt.Errorf("stopContainersAndRun: error querying for containers to stop: %w", err)
+	}
+
+	if len(containersToStop) == 0 {
+		return noop, nil
+	}
+
+	s.logger.Infof(
+		"Stopping %d container(s) labeled `%s` out of %d running container(s).",
+		len(containersToStop),
+		containerLabel,
+		len(allContainers),
+	)
+
+	var stoppedContainers []types.Container
+	var stopErrors []error
+	for _, container := range containersToStop {
+		if err := s.cli.ContainerStop(context.Background(), container.ID, nil); err != nil {
+			stopErrors = append(stopErrors, err)
+		} else {
+			stoppedContainers = append(stoppedContainers, container)
+		}
+	}
+
+	var stopError error
+	if len(stopErrors) != 0 {
+		stopError = fmt.Errorf(
+			"stopContainersAndRun: %d error(s) stopping containers: %w",
+			len(stopErrors),
+			join(stopErrors...),
+		)
+	}
+
+	return func() error {
+		servicesRequiringUpdate := map[string]struct{}{}
+
+		var restartErrors []error
+		for _, container := range stoppedContainers {
+			if swarmServiceName, ok := container.Labels["com.docker.swarm.service.name"]; ok {
+				servicesRequiringUpdate[swarmServiceName] = struct{}{}
+				continue
+			}
+			if err := s.cli.ContainerStart(context.Background(), container.ID, types.ContainerStartOptions{}); err != nil {
+				restartErrors = append(restartErrors, err)
+			}
+		}
+
+		if len(servicesRequiringUpdate) != 0 {
+			services, _ := s.cli.ServiceList(context.Background(), types.ServiceListOptions{})
+			for serviceName := range servicesRequiringUpdate {
+				var serviceMatch swarm.Service
+				for _, service := range services {
+					if service.Spec.Name == serviceName {
+						serviceMatch = service
+						break
+					}
+				}
+				if serviceMatch.ID == "" {
+					return fmt.Errorf("stopContainersAndRun: couldn't find service with name %s", serviceName)
+				}
+				serviceMatch.Spec.TaskTemplate.ForceUpdate = 1
+				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 {
+	s.file = timeutil.Strftime(&s.start, s.file)
+	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(hookLevelCleanup, func(error, time.Time, string) 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(hookLevelCleanup, func(error, time.Time, string) 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(hookLevelCleanup, func(error, time.Time, string) 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 s.mc != nil {
+		if _, err := s.mc.FPutObject(context.Background(), s.c.AwsS3BucketName, 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 _, 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
+}
+
+// pruneOldBackups rotates away backups from local and remote storages using
+// the given configuration. In case the given configuration would delete all
+// backups, it does nothing instead.
+func (s *script) pruneOldBackups() error {
+	if s.c.BackupRetentionDays < 0 {
+		return nil
+	}
+
+	if s.c.BackupPruningLeeway != 0 {
+		s.logger.Infof("Sleeping for %s before pruning backups.", s.c.BackupPruningLeeway)
+		time.Sleep(s.c.BackupPruningLeeway)
+	}
+
+	deadline := time.Now().AddDate(0, 0, -int(s.c.BackupRetentionDays))
+
+	if s.mc != nil {
+		candidates := s.mc.ListObjects(context.Background(), s.c.AwsS3BucketName, minio.ListObjectsOptions{
+			WithMetadata: true,
+			Prefix:       s.c.BackupPruningPrefix,
+		})
+
+		var matches []minio.ObjectInfo
+		var lenCandidates int
+		for candidate := range candidates {
+			lenCandidates++
+			if candidate.Err != nil {
+				return fmt.Errorf(
+					"pruneOldBackups: error looking up candidates from remote storage: %w",
+					candidate.Err,
+				)
+			}
+			if candidate.LastModified.Before(deadline) {
+				matches = append(matches, candidate)
+			}
+		}
+
+		if len(matches) != 0 && len(matches) != lenCandidates {
+			objectsCh := make(chan minio.ObjectInfo)
+			go func() {
+				for _, match := range matches {
+					objectsCh <- match
+				}
+				close(objectsCh)
+			}()
+			errChan := s.mc.RemoveObjects(context.Background(), s.c.AwsS3BucketName, objectsCh, minio.RemoveObjectsOptions{})
+			var removeErrors []error
+			for result := range errChan {
+				if result.Err != nil {
+					removeErrors = append(removeErrors, result.Err)
+				}
+			}
+
+			if len(removeErrors) != 0 {
+				return fmt.Errorf(
+					"pruneOldBackups: %d error(s) removing files from remote storage: %w",
+					len(removeErrors),
+					join(removeErrors...),
+				)
+			}
+			s.logger.Infof(
+				"Pruned %d out of %d remote backup(s) as their age exceeded the configured retention period of %d days.",
+				len(matches),
+				lenCandidates,
+				s.c.BackupRetentionDays,
+			)
+		} else if len(matches) != 0 && len(matches) == lenCandidates {
+			s.logger.Warnf(
+				"The current configuration would delete all %d remote backup copies.",
+				len(matches),
+			)
+			s.logger.Warn("Refusing to do so, please check your configuration.")
+		} else {
+			s.logger.Infof("None of %d remote backup(s) were pruned.", lenCandidates)
+		}
+	}
+
+	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
+		globPattern := path.Join(
+			s.c.BackupArchive,
+			fmt.Sprintf("%s*", s.c.BackupPruningPrefix),
+		)
+		globMatches, err := filepath.Glob(globPattern)
+		if err != nil {
+			return fmt.Errorf(
+				"pruneOldBackups: 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(
+					"pruneOldBackups: 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(
+					"pruneOldBackups: error calling stat on file %s: %w",
+					candidate,
+					err,
+				)
+			}
+			if fi.ModTime().Before(deadline) {
+				matches = append(matches, candidate)
+			}
+		}
+
+		if len(matches) != 0 && len(matches) != len(candidates) {
+			var removeErrors []error
+			for _, match := range matches {
+				if err := os.Remove(match); err != nil {
+					removeErrors = append(removeErrors, err)
+				}
+			}
+			if len(removeErrors) != 0 {
+				return fmt.Errorf(
+					"pruneOldBackups: %d error(s) deleting local files, starting with: %w",
+					len(removeErrors),
+					join(removeErrors...),
+				)
+			}
+			s.logger.Infof(
+				"Pruned %d out of %d local backup(s) as their age exceeded the configured retention period of %d days.",
+				len(matches),
+				len(candidates),
+				s.c.BackupRetentionDays,
+			)
+		} else if len(matches) != 0 && len(matches) == len(candidates) {
+			s.logger.Warnf(
+				"The current configuration would delete all %d local backup copies.",
+				len(matches),
+			)
+			s.logger.Warn("Refusing to do so, please check your configuration.")
+		} else {
+			s.logger.Infof("None of %d local backup(s) were pruned.", len(candidates))
+		}
+	}
+	return nil
+}
+
+// runHooks runs all hooks that have been registered using the
+// given 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, levels ...hookLevel) error {
+	var actionErrors []error
+	for _, level := range levels {
+		for _, hook := range s.hooks {
+			if hook.level != level {
+				continue
+			}
+			if actionErr := hook.action(err, s.start, s.output.String()); actionErr != nil {
+				actionErrors = append(actionErrors, fmt.Errorf("runHooks: error running hook: %w", actionErr))
+			}
+		}
+	}
+	if len(actionErrors) != 0 {
+		return join(actionErrors...)
+	}
+	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)
+	}
+}
+
+// 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
+}
+
+// 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, ", ") + "]")
+}
+
+// buffer takes an io.Writer and returns a wrapped version of the
+// writer that writes to both the original target as well as the returned buffer
+func buffer(w io.Writer) (io.Writer, *bytes.Buffer) {
+	buffering := &bufferingWriter{buf: bytes.Buffer{}, writer: w}
+	return buffering, &buffering.buf
+}
+
+type bufferingWriter struct {
+	buf    bytes.Buffer
+	writer io.Writer
+}
+
+func (b *bufferingWriter) Write(p []byte) (n int, err error) {
+	if n, err := b.buf.Write(p); err != nil {
+		return n, fmt.Errorf("bufferingWriter: error writing to buffer: %w", err)
+	}
+	return b.writer.Write(p)
+}
+
+// hook contains a queued action that can be trigger them when the script
+// reaches a certain point (e.g. unsuccessful backup)
+type hook struct {
+	level  hookLevel
+	action func(err error, start time.Time, logOutput string) error
+}
+
+type hookLevel int
+
+const (
+	hookLevelFailure hookLevel = iota
+	hookLevelCleanup
+)

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 +1,50 @@
+module github.com/offen/docker-volume-backup
+
+go 1.17
+
+require (
+	github.com/docker/docker v20.10.11+incompatible
+	github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df
+	github.com/gofrs/flock v0.8.1
+	github.com/kelseyhightower/envconfig v1.4.0
+	github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d
+	github.com/m90/targz v0.0.0-20210904082215-2e9a4529a615
+	github.com/minio/minio-go/v7 v7.0.16
+	github.com/otiai10/copy v1.7.0
+	github.com/sirupsen/logrus v1.8.1
+	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/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/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/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
+	google.golang.org/genproto v0.0.0-20201110150050-8816d57aaa9a // indirect
+	google.golang.org/grpc v1.33.2 // indirect
+	google.golang.org/protobuf v1.26.0 // indirect
+	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
+	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df // indirect
+	gopkg.in/ini.v1 v1.65.0 // 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 +1,61 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+docker network create test_network
+docker volume create backup_data
+docker volume create app_data
+
+docker run -d \
+  --name minio \
+  --network test_network \
+  --env MINIO_ROOT_USER=test \
+  --env MINIO_ROOT_PASSWORD=test \
+  --env MINIO_ACCESS_KEY=test \
+  --env MINIO_SECRET_KEY=GMusLtUmILge2by+z890kQ \
+  -v backup_data:/data \
+  minio/minio:RELEASE.2020-08-04T23-10-51Z server /data
+
+docker exec minio mkdir -p /data/backup
+
+docker run -d \
+  --name offen \
+  --network test_network \
+  -v app_data:/var/opt/offen/ \
+  offen/offen:latest
+
+sleep 10
+
+docker run --rm \
+  --network test_network \
+  -v app_data:/backup/app_data \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  --env AWS_ACCESS_KEY_ID=test \
+  --env AWS_SECRET_ACCESS_KEY=GMusLtUmILge2by+z890kQ \
+  --env AWS_ENDPOINT=minio:9000 \
+  --env AWS_ENDPOINT_PROTO=http \
+  --env AWS_S3_BUCKET_NAME=backup \
+  --env BACKUP_FILENAME=test.tar.gz \
+  --env "BACKUP_FROM_SNAPSHOT=true" \
+  --entrypoint backup \
+  offen/docker-volume-backup:$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'
+
+echo "[TEST:PASS] Found relevant files in untared backup."
+
+if [ "$(docker ps -q | wc -l)" != "2" ]; then
+  echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
+  docker ps
+  exit 1
+fi
+
+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 +1,47 @@
+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:
+      - backup_data:/data
+
+  backup: &default_backup_service
+    image: offen/docker-volume-backup:${TEST_VERSION}
+    depends_on:
+      - minio
+    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: test.tar.gz
+      BACKUP_LATEST_SYMLINK: test.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
+    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:
+  backup_data:
+  app_data:

test/compose/run.sh

@@ -0,0 +1,58 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec offen ln -s /var/opt/offen/offen.db /var/opt/offen/db.link
+docker-compose exec backup backup
+
+docker run --rm -it \
+  -v compose_backup_data:/data alpine \
+  ash -c 'apk add gnupg && echo 1234secret | gpg -d --pinentry-mode loopback --passphrase-fd 0 --yes /data/backup/test.tar.gz.gpg > /tmp/test.tar.gz && tar -xf /tmp/test.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db'
+
+echo "[TEST:PASS] Found relevant files in untared remote backup."
+
+test -L ./local/test.latest.tar.gz.gpg
+echo 1234secret | gpg -d --yes --passphrase-fd 0 ./local/test.tar.gz.gpg > ./local/decrypted.tar.gz
+tar -xf ./local/decrypted.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db
+rm ./local/decrypted.tar.gz
+test -L /tmp/backup/app_data/db.link
+
+echo "[TEST:PASS] Found relevant files in untared local backup."
+
+if [ "$(docker-compose ps -q | wc -l)" != "3" ]; then
+  echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
+  docker-compose ps
+  exit 1
+fi
+
+echo "[TEST:PASS] All containers running post backup."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+# TODO: find out if we can test actual deletion without having to wait for a day
+BACKUP_RETENTION_DAYS="0" docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+docker run --rm -it \
+  -v compose_backup_data:/data alpine \
+  ash -c '[ $(find /data/backup/ -type f | wc -l) = "1" ]'
+
+echo "[TEST:PASS] Remote backups have not been deleted."
+
+if [ "$(find ./local -type f | wc -l)" != "1" ]; then
+  echo "[TEST:FAIL] Backups should not have been deleted, instead seen:"
+  find ./local -type f
+fi
+
+echo "[TEST:PASS] Local backups have not been deleted."
+
+docker-compose down --volumes

test/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 +1,36 @@
+#!/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 $(docker ps -q -f name=backup) backup
+
+docker run --rm -it \
+  -v test_stack_backup_data:/data alpine \
+  ash -c 'tar -xf /data/backup/test.tar.gz && test -f /backup/pg_data/PG_VERSION'
+
+echo "[TEST:PASS] Found relevant files in untared backup."
+
+if [ "$(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