Description:
Group Replication IPv6 wildcard address/port binding prevents running multiple mysqld instances and group replication on the same server even when configured with different IPv4 addresses.
How to repeat:
Configure a linux server with two virtual IP addresses. Configure the mysql servers group_replication_local_address with the hostnames or IPs and the group replication port (33061). Start up the mysql instances. Bootstrap and start Group Replication on one of the instances. It will bind to the IPv6 wildcard address (:::33061) only if hostname is used. If an IPv4 address is specified for group_replication_local_address it will bind to the IPv4 address on 33061 and the IPv6 wildcard on 33061. Attempt to start group replication on the other mysqld instance. Group Replication will time out attempting to bind to the IPv6 wildcard address and port 33061 that is already in use by the first mysqld instance running group replication.
2025-11-21T13:07:33.258022-05:00 0 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Unable to announce tcp port 33061. Port already in use?'
2025-11-21T13:07:33.258121-05:00 0 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Error initializing the group communication engine.'
2025-11-21T13:07:33.258353-05:00 0 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Unable to start XCom Network Provider'
2025-11-21T13:07:33.258455-05:00 0 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Error joining the group while waiting for the network layer to become ready.'
2025-11-21T13:07:33.309701-05:00 0 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] The member was unable to join the group. Local port: 33061'
Suggested fix:
Bind to IPv4 or IPv6 based on the configuration of group_replication_local_address.
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