6.2.4 Persisting Settings

The AdminAPI commands you use to work with an InnoDB Cluster, InnoDB ClusterSet, InnoDB ReplicaSet, and the individual member server instances in these deployments modify the configuration of MySQL Server on the instance. Depending on the way MySQL Shell is connected to an instance and the version of MySQL Server installed on the instance, these configuration changes can be persisted to the instance automatically.

By making settings to the instance persistent, you ensure that after the instance restarts, configuration changes are retained. For background information see SET PERSIST. This persistence is essential for reliable usage. For example, if settings are not persistent, an instance added to a cluster does not rejoin the cluster after a restart because configuration changes are lost.

Instances which meet the following requirements support persisting configuration changes automatically:

• The instance is running MySQL version 8.0.11 or later.

• persisted_globals_load is set to ON.

• The instance has not been started with the --no-defaults option.

Instances which do not meet these requirements do not support persisting configuration changes automatically, and when AdminAPI operations result in changes to the instance's settings to be persisted you receive warnings such as:

WARNING: On instance 'localhost:3320' membership change cannot be persisted since MySQL version 5.7.21
does not support the SET PERSIST command (MySQL version >= 8.0.5 required). Please use the
<Dba>.configureLocalInstance command locally to persist the changes.

When AdminAPI commands are issued against the MySQL instance which MySQL Shell is currently running on, in other words, the local instance, MySQL Shell persists configuration changes directly to the instance. On local instances which support persisting configuration changes automatically, configuration changes are persisted to the instance's mysqld-auto.cnf file, and the configuration change does not require any further steps.

You must make the changes locally on local instances that do not support persisting configuration changes automatically. For more information, see Configuring Instances with dba.configureLocalInstance().

When run against a remote instance, in other words, an instance other than the one which MySQL Shell is currently running on, if the instance supports persisting configuration changes automatically, the AdminAPI commands persist configuration changes to the instance's mysql-auto.conf option file.

If a remote instance does not support persisting configuration changes automatically, the AdminAPI commands can not automatically configure the instance's option file. So, the AdminAPI commands can read information from the instance, for example, to display the current configuration. But changes to the configuration cannot be persisted to the instance's option file. In this case, you need to persist the changes locally. For more information, see Configuring Instances with dba.configureLocalInstance().