7.5.7 InnoDB Cluster and Auto-increment

When you are using an instance as part of an InnoDB Cluster, the auto_increment_increment and auto_increment_offset variables are configured to avoid the possibility of auto increment collisions for multi-primary clusters up to a size of 9 (the maximum supported size of a Group Replication group). The logic used to configure these variables can be summarized as:

• If the group is running in single-primary mode, then set auto_increment_increment to 1 and auto_increment_offset to 2.

• If the group is running in multi-primary mode, then when the cluster has 7 instances or less set auto_increment_increment to 7 and auto_increment_offset to 1 + server_id % 7. If a multi-primary cluster has 8 or more instances set auto_increment_increment to the number of instances and auto_increment_offset to 1 + server_id % the number of instances.