7.5.4 Configuring Failover Consistency

Group Replication provides the ability to specify the failover guarantees if a primary failover happens in single-primary mode (see Configuring Transaction Consistency Guarantees). You can configure the failover guarantees of an InnoDB Cluster at creation by passing the consistency option While the fencing mechanism is in place, applications effectively do not see time going backward for a short period of time while any backlog is applied. This ensures that applications do not read stale information from the newly elected primary.

The consistency option is only supported if the target MySQL server version is 8.0.14 or later, and instances added to a cluster which has been configured with the consistency option are automatically configured to have group_replication_consistency the same on all cluster members that have support for the option. The variable default value is controlled by Group Replication and is BEFORE_ON_PRIMARY_FAILOVER on MySQL 8.4.0 and higher, EVENTUAL on older versions.

Note

Using the consistency option on a multi-primary InnoDB Cluster has no effect but is allowed because the cluster can later be changed into single-primary mode with the Cluster.switchToSinglePrimaryMode() operation.