debian-mirror-gitlab/doc/update/restore_after_failure.md

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Restoring from backup after a failed upgrade (FREE SELF)

Upgrades are usually smooth and restoring from backup is a rare occurrence. However, it's important to know how to recover when problems do arise.

Roll back to an earlier version and restore a backup

In some cases after a failed upgrade, the fastest solution is to roll back to the previous version you were using. We recommend this path because the failed upgrade might have made database changes that cannot be readily reverted.

First, roll back the code or package. For source installations this involves checking out the older version (branch or tag). For Omnibus installations this means installing the older .deb or .rpm package. Then, restore from a backup. Follow the instructions in the Backup and Restore documentation.

Potential problems on the next upgrade

When a rollback is necessary it can produce problems on subsequent upgrade attempts. This is because some tables may have been added during the failed upgrade. If these tables are still present after you restore from the older backup it can lead to migration failures on future upgrades.

We drop all tables prior to importing the backup to prevent this problem.

Example error:

== 20151103134857 CreateLfsObjects: migrating =================================
-- create_table(:lfs_objects)
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

PG::DuplicateTable: ERROR:  relation "lfs_objects" already exists

Copy the version from the error. In this case the version number is 20151103134857.

WARNING: Use the following steps only if you are certain you must do them.

1. Pass the version to a database Rake task to manually mark the migration as complete.

   # Source install
   sudo -u git -H bundle exec rake gitlab:db:mark_migration_complete[20151103134857] RAILS_ENV=production
   
   # Omnibus install
   sudo gitlab-rake gitlab:db:mark_migration_complete[20151103134857]
   

2. After the migration is successfully marked, run the Rake db:migrate task again.

3. Repeat this process until all failed migrations are complete.