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Percona Documentation

Failover

In case of the Main site failure or in other cases, you can promote the standby cluster. The promotion effectively allows writing to the cluster. This creates a net effect of pushing Write Ahead Logs (WALs) to the pgBackrest repository. It might create a split-brain situation where two primary instances attempt to write to the same repository. To avoid this, make sure the primary cluster is either deleted or shut down before trying to promote the standby cluster.

Once the primary is down or inactive, promote the standby through changing the corresponding section:

spec:
  standby:
    enabled: false

Now you can start writing to the cluster.

Split brain

There might be a case, where your old primary comes up and starts writing to the repository. To recover from this situation, do the following:

  1. Keep only one primary with the latest data running
  2. Stop the writes on the other one
  3. Take the new full backup from the primary and upload it to the repo

Automate the failover

Automated failover consists of multiple steps and is outside of the Operator’s scope. There are a few steps that you can take to reduce the Recovery Time Objective (RTO). To detect the failover we recommend having the 3rd site to monitor both DR and Main sites. In this case you can be sure that Main really failed and it is not a network split situation.

Another aspect of automation is to switch the traffic for the application from Main to Standby after promotion. It can be done through various Kubernetes configurations and heavily depends on how your networking and application are designed. The following options are quite common:

  1. Global Load Balancer - various clouds and vendors provide their solutions
  2. Multi Cluster Services or MCS - available on most of the public clouds
  3. Federation or other multi-cluster solutions

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Last update: 2024-10-08