If you have an existing deployment of Group Replication and you want to use it to create a cluster, pass the adoptFromGR option to the dba.createCluster() function. The created InnoDB Cluster matches whether the replication group is running as single-primary or multi-primary.
To adopt an existing Group Replication group, connect to a group member using MySQL Shell. In the following example a single-primary group is adopted. We connect to gr-member-2, a secondary instance, while gr-member-1 is functioning as the group’s primary. Create a cluster using dba.createCluster(), passing in the adoptFromGR option. For example:
mysql-js> var cluster = dba.createCluster(‘prodCluster’, {adoptFromGR: true});
A new InnoDB cluster will be created on instance ‘root@gr-member-2:3306’.
Creating InnoDB cluster ‘prodCluster’ on ‘root@gr-member-2:3306’…
Adding Seed Instance…
Cluster successfully created. Use cluster.addInstance() to add MySQL instances.
At least 3 instances are needed for the cluster to be able to withstand up to
one server failure.
Tip
If the instance has super_read_only=ON then you might need to confirm that AdminAPI can set super_read_only=OFF. See Instance Configuration in Super Read-only Mode for more information.
If you do not specify adoptFromGR: true, and the target server instance belongs to a replication group, MySQL Shell prompts you to confirm whether you want to adopt the replication group. From MySQL Shell 8.0.29, if you specify adoptFromGR: false, the operation is stopped with no prompt if the instance is found to belong to a replication group.
The new cluster matches the mode of the group. If the adopted group was running in single-primary mode then a single-primary cluster is created. If the adopted group was running in multi-primary mode then a multi-primary cluster is created.
Note
It is not possible to define the communication stack used by the cluster in the same command as adoptFromGR, the cluster must initially use the communication stack used by the adopted group. If necessary, you can change the communication stack after the group is adopted using rebootClusterFromCompleteOutage. See Section 7.5.9, “Configuring the Group Replication Communication Stack”.
