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Nobody wants backup. Everybody wants restore.

Operations matter. I know the Hipster crowd does not like to hear that, cloud or not. But reality has a way of making itself heard, whether you like it or not. just discovered that.

So some sysadmin deleted the wrong folder, which in itself should not be a problem. But in the process of trying to restore things, the following discoveries have been made:

  • LVM snapshots are by default only taken once every 24 hours. YP happened to run one manually about 6 hours prior to the outage
  • Regular backups seem to also only be taken once per 24 hours, though YP has not yet been able to figure out where they are stored. According to JN these don’t appear to be working, producing files only a few bytes in size.
  • SH: It looks like pg_dump may be failing because PostgreSQL 9.2 binaries are being run instead of 9.6 binaries. This happens because omnibus only uses Pg 9.6 if data/PG_VERSION is set to 9.6, but on workers this file does not exist. As a result it defaults to 9.2, failing silently. No SQL dumps were made as a result. Fog gem may have cleaned out older backups.
  • Disk snapshots in Azure are enabled for the NFS server, but not for the DB servers.
  • The synchronisation process removes webhooks once it has synchronised data to staging. Unless we can pull these from a regular backup from the past 24 hours they will be lostThe replication procedure is super fragile, prone to error, relies on a handful of random shell scripts, and is badly documented
  • Our backups to S3 apparently don’t work either: the bucket is empty

If you think your sysadmin is paranoid, let this be your lesson. They are not. Operations do matter, even (especially) in the cloud.

EDIT: Michael Renner asks some interesting questions:

»Some thoughts for GitLab: What is WAL shipping? What is pgbouncer? Why does everyone hate Slony? Why is EC2 so slow?«

Tweet: @Terrorobe

People using Slony on a Postgres 9.6 deserve everything that happens to them. Slony is trigger based replication breakage from the deepest circles of hell, and Postgres has excellent, stable and fast internal replications since several years now. Also, what he says about log shipping: There is no reason at all to lose any write ever on a Postgres, nor to have much downtime at all with proper replication.

Operations do matter. Cloud ain’t gonna change that.

EDIT: Dedicating 1st of February as “Check your Backups Day”

Check your Backups Day
Published inData Centers


  1. Hartmut Holzgraefe

    Even if all items on the list had worked as expected they’d still be facing problems though as none of them allows for point-in-time recovery? Or am I missing something?

  2. Christoph

    They do use streaming replication – they’ve mentioned “max_wal_senders” which you wouldn’t need for trigger-based replication. In fact, the only mention of Slony was as a tool for upgrading PostgreSQL 9.2 to 9.6 – and there were no really good tools to online-upgrade 9.2 (that changed only in 9.4).
    That doesn’t excuse their lack of WAL archiving (no PITR for you) and their lack of backup testing (sheesh, not noticing that your backups are failing…).

  3. Andreas Kostyrka

    Well, from personal experience, slony should probably be called “world record breaking mule”. The experience is now safely over a decade old, but I can still remember playing nursemaid for slony. Fragile and brittle, with a bad temperament.

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