Bug #102583 Instance not fully removed after doing cluster.removeInstance with wrong case
Submitted: 12 Feb 15:16 Modified: 16 Feb 14:12
Reporter: Keith Lammers Email Updates:
Status: Verified Impact on me:
None 
Category:Shell AdminAPI InnoDB Cluster / ReplicaSet Severity:S3 (Non-critical)
Version:8.0.23 OS:Microsoft Windows
Assigned to: CPU Architecture:Any

[12 Feb 15:16] Keith Lammers
Description:
If you use a lower-case instance name in cluster.removeInstance, the instance will have group replication stopped, but will not be removed from the cluster metadata.

I worked with Miguel Araujo on this, here are some further details:

verbose: 2021-02-12T09:39:54Z: instance01:3306: DELETE FROM mysql_innodb_cluster_metadata.instances WHERE addresses->'$.mysqlClassic' = 'instance02:3306'
This query doesn't do anything, because this is what's registered in the metadata:
addresses: {"mysqlX": "INSTANCE02:33060", "grLocal": "INSTANCE02:33061", "mysqlClassic": "INSTANCE02:3306"}
But then shell issues this query on that instance: STOP GROUP_REPLICATION, so group_replication stops, and the instance leaves the group, but it's not removed from the metadata and that's why it's shown as (MISSING) in .status()

How to repeat:
* Create a 3 node InnoDB Cluster
* Run dba.removeInstance('instance02'), AdminAPI will state that the instance was successfully removed
* Run cluster.status(), the instance is still listed and shown as offline

* If you do cluster.rescan() and choose yes when prompted to remove the missing instance, it will be removed from the metadata
* If you then add it back with cluster.addInstance(), and then do cluster.removeInstance('INSTANCE02'), it will be removed from the cluster metadata successfully

Suggested fix:
Don't allow the user to run dba.removeInstance with a lower-case instance name.
[16 Feb 14:12] MySQL Verification Team
Hello Keith,

Thank you for the report and feedback.
Verified as described.

regards,
Umesh