It is possible to have several ClusterControl servers to monitor a single cluster. This is useful if you have a multi-datacenter cluster and you may need to have ClusterControl on the remote site to monitor and manage the alive nodes if the connection between them goes down. However, ClusterControl servers must be configured to be working in active-passive mode to avoid race conditions when digesting queries and recovering failed nodes or clusters.
In the active mode, the ClusterControl node act as a primary controller, where it performs automatic recovery and parsing MySQL slow log query for query monitoring. The secondary ClusterControl node however must have the following things configured:
- Cluster/Node auto-recovery must be turned off.
- Query sampling must be disabled (only if Performance_Schema is disabled on the database nodes).
Installing Standby Server
Steps described in this section must be performed on the secondary ClusterControl server.
- Install ClusterControl as explained on the Getting Started page.
- Add the same cluster via ClusterControl → Import. Ensure you choose “Enable Node AutoRecovery: No” and “Enable Cluster AutoRecovery: No” in the dialog box. Click “Add Cluster” to start the import job.
- Once the cluster is imported, disable query sampling by going to ClusterControl → Query Monitor → Top Queries → Toggle Off.
Nothing should be performed on the primary side. The primary ClusterControl server shall perform automatic recovery in case of node or cluster failure.
If you want to make the standby server runs in the active mode, just do as follow (assume the primary ClusterControl is unreachable at the moment):
- Cluster/Node auto-recovery must be turned on. Click on both red power icons in the summary bar until they appear in green color.
- Enable query sampling by going to ClusterControl → Query Monitor → Top Queries → Toggle On.
That’s it. At this point, the standby server has taken over the primary role.
Do not let two or more ClusterControl instances perform automatic recovery to the same cluster at one time.