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Original files and derivatives

These are stored in S3, and are backed up within S3 by a process managed by AWS. The backups are then copied to long-term storage by SyncBackPro, which is Windows software running on Promethium managed by Chuck and Ponce (see https://www.2brightsparks.com/syncback/sbpro.html ). (None of this will change when we get rid of Ansible.)

Heroku database backups

We have three backup mechanisms under Heroku:

1. Continuous protection

Heroku offers us a behind-the-scenes Continuous Protection mechanism for database disaster recovery. This doesn’t involve any actual backup files that we can see or download. It does ensures that, in the event of a disaster, we can create a rollback database in under an hour

2. Nightly physical backups

We supplement the above with a regular, 2am, nightly physical database scheduled backup. These are stored by Heroku, and restoring to them is convenient and takes well under a minute. Heroku retains up to 25 of these.

heroku pg:backups:schedules --app scihist-digicoll-production

(Physical backups are binary files that include dead tuples, bloat, indexes and all structural characteristics of the currently running database.)

List backups by running heroku pg:backups.

Restoring from a nightly physical backup

For physical backups retained by Heroku (we retain up to 25) a restore takes about a minute and works like this:

heroku pg:backups:restore --app scihist-digicoll-production

Downloading a physical backup to a local “.dump” file

heroku pg:backups:download a006 will produce a file like:

$ file physical.dump
physical.dump: PostgreSQL custom database dump - v1.14-0

(lightbulb) Note that a physical dump can be converted to a garden-variety “logical” .sql database file:

$ pg_restore -f logical_database_file.sql physical.dump.

$ file logical_database_file.sql
logical_database_file.sql: UTF-8 Unicode text, with very long lines

Restoring from a physical backup stored as a local “.dump” file

If you downloaded a physical backup which is now stored on your local machine, and want to restore from that specific file, you will first need to upload it to s3, create a signed URL for the dump, and finally run:

heroku pg:backups:restore '<SIGNED_URL_IN_S3>' DATABASE_URL # note the (DATABASE_URL is a literal, not a placeholder.)

More details on this process, including how to create a signed s3 URL: https://devcenter.heroku.com/articles/heroku-postgres-import-export#import

3. Preservation (logical) backups to s3

Finally, we maintain a rake task, rake scihist:copy_database_to_s3, which runs on a one-off Heroku dyno, via the scheduler. This uploads a logical (plain vanilla SQL) database to s3, where SyncBackPro then syncs to tape (this process, again, is managed by Chuck and Ponce.)

This workflow serves more for preservation than for disaster recovery: logical .sql files offer portability (they’re UTF8), and are useful in a variety of situations; notably, they can be used to reconstruct the database, even on other machines and other architectures using psql -f db.sql.

Given the size of the database in late 2020, the entire job (with the overhead of starting up the dyno and tearing it down) takes a bit under a minute. However, if our database grows much larger (20GB or more) we will probably have to get rid of these frequent logical backups.

SyncBackPro on Promethium (managed by Chuck and Ponce) finally copies the S3 file to a local network storage mount (/media/SciHist_Digicoll_Backup), and that gets backed up to tape.

Restoring from a logical (.sql) database dump.

In the unlikely event you have to restore from a logical backup, because you can’t use the continuous protection rollback, and all the dumps managed by Heroku are somehow unavailable:

Historical notes

Prior to moving off our Ansible-managed servers, we used backup mechanisms that used to be performed by cron jobs installed by Ansible.Backups and Recovery contains a summary of our pre-Heroku backup infrastructure.

A script on the production server, home/ubuntu/bin/postgres-backup.sh, used to perform the following tasks nightly:

  • pg_dump the production database to /backups/pgsql-backup/.

  • aws s3 sync the contents of that directory to s3://chf-hydra-backup/PGSql.

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