debian-mirror-gitlab/doc/administration/geo/disaster_recovery/bring_primary_back.md

Bring a demoted primary node back online (PREMIUM ONLY)

After a failover, it is possible to fail back to the demoted primary node to restore your original configuration. This process consists of two steps:

1. Making the old primary node a secondary node.
2. Promoting a secondary node to a primary node.

CAUTION: Caution: If you have any doubts about the consistency of the data on this node, we recommend setting it up from scratch.

Configure the former primary node to be a secondary node

Since the former primary node will be out of sync with the current primary node, the first step is to bring the former primary node up to date. Note, deletion of data stored on disk like repositories and uploads will not be replayed when bringing the former primary node back into sync, which may result in increased disk usage. Alternatively, you can set up a new secondary GitLab instance to avoid this.

To bring the former primary node up to date:

1. SSH into the former primary node that has fallen behind.

2. Make sure all the services are up:

   sudo gitlab-ctl start
   

   NOTE: Note: If you disabled the primary node permanently, you need to undo those steps now. For Debian/Ubuntu you just need to run sudo systemctl enable gitlab-runsvdir. For CentOS 6, you need to install the GitLab instance from scratch and set it up as a secondary node by following Setup instructions. In this case, you don't need to follow the next step.

   NOTE: Note: If you changed the DNS records for this node during disaster recovery procedure you may need to block all the writes to this node during this procedure.

3. Setup database replication. Note that in this case, primary node refers to the current primary node, and secondary node refers to the former primary node.

If you have lost your original primary node, follow the setup instructions to set up a new secondary node.

Promote the secondary node to primary node

When the initial replication is complete and the primary node and secondary node are closely in sync, you can do a planned failover.

Restore the secondary node

If your objective is to have two nodes again, you need to bring your secondary node back online as well by repeating the first step (configure the former primary node to be a secondary node) for the secondary node.