Unable to add or delete database servers from a cluster

Overview

Internal inconsistencies in the cluster configuration database can sometimes result in the inability to add or delete database servers from a ScaleArc cluster. When trying to add or delete a database server from the cluster on the primary server in a HA pair, ScaleArc will give an error stating that it was unable to update the setting on the secondary server even though the action was done on the primary node in the HA pair.

This article describes how to recover a ScaleArc HA environment experiencing this error.

Environment

  • ScaleArc for MySQL
  • HA configuration
  • MySQL database running as Percona XtraDB Cluster

Solution

Checking the HA Settings will show both servers in a HA pair as secondary servers when there are internal inconsistencies in the cluster configuration database resulting in the inability to add or delete databases from the ScaleArc cluster.

Follow these steps to resolve this problem:

  1. Create a new ScaleArc cluster for the Percona XtraDB Cluster and add the Percona XtraDB Cluster database server nodes.
  2. Configure the new cluster as the HA witness as described in Setting up HA.
  3. Stop and delete the previously configured cluster as described in Managing a Cluster.
  4. On the newly created cluster, configure the Synchronous replication type to match the Percona XtraDB cluster type. 
  5. Enable the Auto-failover feature and perform manual failover tests to validate the new HA configuration.
Tip: It is recommended to always upgrade ScaleArc to the latest GA release available from the Release Portal.

Testing

It should now be possible to add and delete database servers from the recreated cluster.

Manual failover testing should execute as expected without errors.

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