Caution: This runbook is in alpha. For complete, production-ready documentation, see the disaster recovery documentation.

Disaster Recovery (Geo) promotion runbooks

Geo planned failover for a multi-node configuration

Component Configuration
PostgreSQL Omnibus-managed
Geo site Multi-node
Secondaries One

This runbook will guide you through a planned failover of a multi-node Geo site with one secondary. The following 2000 user reference architecture is assumed:

graph TD subgraph main[Geo deployment] subgraph Primary[Primary site, multi-node] Node_1[Rails node 1] Node_2[Rails node 2] Node_3[PostgreSQL node] Node_4[Gitaly node] Node_5[Redis node] Node_6[Monitoring node] end subgraph Secondary[Secondary site, multi-node] Node_7[Rails node 1] Node_8[Rails node 2] Node_9[PostgreSQL node] Node_10[Gitaly node] Node_11[Redis node] Node_12[Monitoring node] end end

The load balancer node and optional NFS server are omitted for clarity.

This guide will result in the following:

  1. An offline primary.
  2. A promoted secondary that is now the new primary.

What is not covered:

  1. Re-adding the old primary as a secondary.
  2. Adding a new secondary.

Preparation

Note: Before following any of those steps, make sure you have root access to the secondary to promote it, since there isn’t provided an automated way to promote a Geo replica and perform a failover.

On the secondary node, navigate to the Admin Area > Geo dashboard to review its status. Replicated objects (shown in green) should be close to 100%, and there should be no failures (shown in red). If a large proportion of objects aren’t yet replicated (shown in gray), consider giving the node more time to complete.

Replication status

If any objects are failing to replicate, this should be investigated before scheduling the maintenance window. After a planned failover, anything that failed to replicate will be lost.

You can use the Geo status API to review failed objects and the reasons for failure. A common cause of replication failures is the data being missing on the primary node - you can resolve these failures by restoring the data from backup, or removing references to the missing data.

The maintenance window won’t end until Geo replication and verification is completely finished. To keep the window as short as possible, you should ensure these processes are close to 100% as possible during active use.

If the secondary node is still replicating data from the primary node, follow these steps to avoid unnecessary data loss:

  1. Until a read-only mode is implemented, updates must be prevented from happening manually to the primary. Note that your secondary node still needs read-only access to the primary node during the maintenance window:

    1. At the scheduled time, using your cloud provider or your node’s firewall, block all HTTP, HTTPS and SSH traffic to/from the primary node, except for your IP and the secondary node’s IP.

      For instance, you can run the following commands on the primary node:

      sudo iptables -A INPUT -p tcp -s <secondary_node_ip> --destination-port 22 -j ACCEPT
      sudo iptables -A INPUT -p tcp -s <your_ip> --destination-port 22 -j ACCEPT
      sudo iptables -A INPUT --destination-port 22 -j REJECT
      
      sudo iptables -A INPUT -p tcp -s <secondary_node_ip> --destination-port 80 -j ACCEPT
      sudo iptables -A INPUT -p tcp -s <your_ip> --destination-port 80 -j ACCEPT
      sudo iptables -A INPUT --tcp-dport 80 -j REJECT
      
      sudo iptables -A INPUT -p tcp -s <secondary_node_ip> --destination-port 443 -j ACCEPT
      sudo iptables -A INPUT -p tcp -s <your_ip> --destination-port 443 -j ACCEPT
      sudo iptables -A INPUT --tcp-dport 443 -j REJECT
      

      From this point, users will be unable to view their data or make changes on the primary node. They will also be unable to log in to the secondary node. However, existing sessions will work for the remainder of the maintenance period, and public data will be accessible throughout.

    2. Verify the primary node is blocked to HTTP traffic by visiting it in browser via another IP. The server should refuse connection.

    3. Verify the primary node is blocked to Git over SSH traffic by attempting to pull an existing Git repository with an SSH remote URL. The server should refuse connection.

    4. On the primary node, disable non-Geo periodic background jobs by navigating to Admin Area > Monitoring > Background Jobs > Cron, clicking Disable All, and then clicking Enable for the geo_sidekiq_cron_config_worker cron job. This job will re-enable several other cron jobs that are essential for planned failover to complete successfully.

  2. Finish replicating and verifying all data:

    Caution: Not all data is automatically replicated. Read more about what is excluded.
    1. If you are manually replicating any data not managed by Geo, trigger the final replication process now.
    2. On the primary node, navigate to Admin Area > Monitoring > Background Jobs > Queues and wait for all queues except those with geo in the name to drop to 0. These queues contain work that has been submitted by your users; failing over before it is completed will cause the work to be lost.
    3. On the primary node, navigate to Admin Area > Geo and wait for the following conditions to be true of the secondary node you are failing over to:
      • All replication meters to each 100% replicated, 0% failures.
      • All verification meters reach 100% verified, 0% failures.
      • Database replication lag is 0ms.
      • The Geo log cursor is up to date (0 events behind).
    4. On the secondary node, navigate to Admin Area > Monitoring > Background Jobs > Queues and wait for all the geo queues to drop to 0 queued and 0 running jobs.
    5. On the secondary node, use these instructions to verify the integrity of CI artifacts, LFS objects, and uploads in file storage.

    At this point, your secondary node will contain an up-to-date copy of everything the primary node has, meaning nothing will be lost when you fail over.

  3. In this final step, you need to permanently disable the primary node.

    Caution: When the primary node goes offline, there may be data saved on the primary node that has not been replicated to the secondary node. This data should be treated as lost if you proceed.
    Tip: If you plan to update the primary domain DNS record, you may wish to lower the TTL now to speed up propagation.

    When performing a failover, we want to avoid a split-brain situation where writes can occur in two different GitLab instances. So to prepare for the failover, you must disable the primary node:

    • If you have SSH access to the primary node, stop and disable GitLab:

      sudo gitlab-ctl stop
      

      Prevent GitLab from starting up again if the server unexpectedly reboots:

      sudo systemctl disable gitlab-runsvdir
      
      Note: (CentOS only) In CentOS 6 or older, there is no easy way to prevent GitLab from being started if the machine reboots isn’t available (see Omnibus GitLab issue #3058). It may be safest to uninstall the GitLab package completely with sudo yum remove gitlab-ee.
      Note: (Ubuntu 14.04 LTS) If you are using an older version of Ubuntu or any other distribution based on the Upstart init system, you can prevent GitLab from starting if the machine reboots as root with initctl stop gitlab-runsvvdir && echo 'manual' > /etc/init/gitlab-runsvdir.override && initctl reload-configuration.
    • If you do not have SSH access to the primary node, take the machine offline and prevent it from rebooting. Since there are many ways you may prefer to accomplish this, we will avoid a single recommendation. You may need to:

      • Reconfigure the load balancers.
      • Change DNS records (for example, point the primary DNS record to the secondary node to stop using the primary node).
      • Stop the virtual servers.
      • Block traffic through a firewall.
      • Revoke object storage permissions from the primary node.
      • Physically disconnect a machine.

Promoting the secondary node

Note: A new secondary should not be added at this time. If you want to add a new secondary, do this after you have completed the entire process of promoting the secondary to the primary.
Caution: If you encounter an ActiveRecord::RecordInvalid: Validation failed: Name has already been taken error during this process, read the troubleshooting advice.

The gitlab-ctl promote-to-primary-node command cannot be used yet in conjunction with multiple servers, as it can only perform changes on a secondary with only a single machine. Instead, you must do this manually.

Warning: In GitLab 13.2 and later versions, promoting a secondary node to a primary while the secondary is paused fails. We are investigating the issue. Do not pause replication before promoting a secondary. If the node is paused, please resume before promoting.
  1. SSH in to the PostgreSQL node in the secondary and trigger PostgreSQL to promote to read-write:

    sudo gitlab-pg-ctl promote
    

    In GitLab 12.8 and earlier, see Message: sudo: gitlab-pg-ctl: command not found.

  2. Edit /etc/gitlab/gitlab.rb on every machine in the secondary to reflect its new status as primary by removing any lines that enabled the geo_secondary_role:

    ## In pre-11.5 documentation, the role was enabled as follows. Remove this line.
    geo_secondary_role['enable'] = true
    
    ## In 11.5+ documentation, the role was enabled as follows. Remove this line.
    roles ['geo_secondary_role']
    

    After making these changes Reconfigure GitLab each machine so the changes take effect.

  3. Promote the secondary to primary. SSH into a single Rails node server and execute:

    sudo gitlab-rake geo:set_secondary_as_primary
    
  4. Verify you can connect to the newly promoted primary using the URL used previously for the secondary.

  5. Success! The secondary has now been promoted to primary.

Next steps

To regain geographic redundancy as quickly as possible, you should add a new secondary node. To do that, you can re-add the old primary as a new secondary and bring it back online.