Docker PostgreSQL Backup

Docker image that periodically dumps a Postgres database, and uploads it to an Amazon S3 bucket.

Required environment variables

• CRON_SCHEDULE: The time schedule part of a crontab file (e.g: 15 3 * * * for every night 03:15)
• DB_HOST: Postgres hostname
• DB_PASS: Postgres password
• DB_USER: Postgres username
• DB_NAME: Name of database
• S3_PATH: Amazon S3 path in the format: s3://bucket-name/some/path
• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_DEFAULT_REGION

Optional environment variables

• S3_STORAGE_CLASS: Specify storage class for the uploaded object, defaults to STANDARD_IA.
• S3_EXTRA_OPTIONS: Specify additional options for S3, e.g. --endpoint= for using custom S3 provider.
• DB_USE_ENV: Inject postgres environment variables from the environment. Ignores DB_HOST, DB_PASS, DB_USER and DB_NAME. Can be used to specify advanced connections, e.g. using mTLS connection. Example of --env-file=.env for container:

      DB_USE_ENV=True
      PGSSLMODE=verify-full
      PGSSLROOTCERT=/path/ca.crt
      PGSSLCERT=<path>/user.crt
      PGSSLKEY=<path>/user.key
      PGHOSTADDR=1.2.3.4
      PGHOST=db.domain.com
      PGUSER=myuser
      PGDATABASE=mydb
  

• MAIL_TO: If MAIL_TO and MAIL_FROM is specified, an e-mail will be sent, using Amazon SES, every time a backup is taken
• MAIL_FROM
• WEBHOOK: If specified, an HTTP request will be sent to this URL
• WEBHOOK_METHOD: By default the webhook's HTTP method is GET, but can be changed using this variable
• WEBHOOK_CURL_OPTIONS: Add additional headers or other option to curl command calling the webhook. E.g. -H 'Content-type: application/json'
• WEBHOOK_DATA: Add a body to the webhook being called, unless changed it implies that POST method is used. E.g. {"text":"Backup completed at %(date)s %(time)s!"}
• KEEP_BACKUP_DAYS: The number of days to keep backups for when pruning old backups. Defaults to 7.
• FILENAME: String that is passed into strftime() and used as the backup dump's filename. Defaults to $DB_NAME_%Y-%m-%d.

Interpolation

Text in WEBHOOK_DATA is interpolated with variabels %(my_var)s

• date: Date in yyyy-mm-dd format
• time: Date in hh:mm:ss format
• duration: Number of seconds take to backup
• filename: Name of the file uploaded to S3
• size: Size of the backup file with suitable suffix, like MB, GB, ...

Example on how to post a Slack message when a backup is complete

1. Configure a webhook as described in the Slack documentation.
2. Set WEBHOOK and WEBHOOK_ accodringly:

   WEBHOOK=https://hooks.slack.com/services/.../.../...
   WEBHOOK_METHOD=POST
   WEBHOOK_CURL_OPTIONS=-H 'Content-type: application/json'
   WEBHOOK_DATA={"text":":white_check_mark: Backup completed at %(date)s %(time)s\nDuration: %(duration)s seconds\nUpload: %(filename)s: %(size)s"}
   

Volumes

• /data/backups - The database is dumped in into this directory

Restoring a backup

This image can also be run as a one off task to restore one of the backups. To do this, we run the container with the command: python -u /backup/restore.py [S3-filename] (S3-filename should only be the name of the file, the directory is set through the S3_PATH env variable).

The following environment variables are required:

• DB_HOST: Postgres hostname
• DB_PASS: Postgres password
• DB_USER: Postgres username
• DB_NAME: Name of database to import into
• S3_PATH: Amazon S3 directory path in the format: s3://bucket-name/some/path
• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_DEFAULT_REGION

Other optional environment variables

• S3_EXTRA_OPTIONS: Specify additional options for S3, e.g. --endpoint= for using custom S3 provider.
• DB_USE_ENV: See Optional environment variables above.

Taking a one off backup

To run a one off backup job, e.g. to test that it works when setting it up for the first time, simply start the container with the docker run command set to python -u /backup/backup.py (as well as all the required environment variables set).

Docker tags

This image uses the alpine version(s) of the official postgres image as base image.

The following docker tags are available for this image, and they are based on the corresponding official postgres alpine image:

• 13, latest
• 12
• 11
• 10