MySQL could not join the Group Replication communication group when START GROUP_REPLICATION was executed.
ER_GROUP_REPLICATION_COMMUNICATION_LAYER_JOIN_ERROR happens when a MySQL node cannot join the Group Replication communication group due to mismatched credentials, unreachable ports, or incompatible plugin settings. Check group_replication_local_address, ensure ports 33061/33062 are open, and verify SSL keys to resolve the issue.
ER_GROUP_REPLICATION_COMMUNICATION_LAYER_JOIN_ERROR
ER_GROUP_REPLICATION_COMMUNICATION_LAYER_JOIN_ERROR is MySQL error 3097 returned when a server fails to join the Group Replication communication group during START GROUP_REPLICATION. The replication plugin aborts before the node establishes group membership, leaving the instance in standalone mode.
The error was introduced in MySQL 5.7.6 and appears in later 5.7, 8.0 and 8.1 releases. Resolving it quickly is vital because a node that cannot join the group cannot participate in distributed transactions or quorum voting.
Most cases trace to network connectivity problems or misconfigured replication variables. The Group Replication plugin needs open UDP/TCP ports, matching view IDs, and compatible SSL keys. Any mismatch forces an immediate join failure.
In cloud or container environments, firewalls or NAT rules often block the group_replication_local_address port, preventing the internal XCom layer from forming a connection with peer nodes.
First validate that group_replication_local_address and group_replication_group_seeds list reachable host:port pairs. All peers must agree on the same port, usually 33061.
Next, confirm operating system firewalls and cloud security groups allow inbound and outbound traffic on the group replication port. Temporarily disable the firewall to test.
If the error appears only on new nodes, check SSL certificates referenced by group_replication_ssl_* variables. Expired or mismatched certificates block the join handshake.
When every node shows the error after a version upgrade, verify that all servers run the same MySQL major and minor version. Mixed versions can prevent view agreement.
Automate configuration with templates to guarantee identical group_replication_* settings across nodes. Store seed lists in DNS SRV records to simplify scaling.
Continuously monitor performance_schema.replication_group_members for STATE = ERROR to alert operators before applications notice an outage.
ER_GROUP_REPLICATION_COMMUNICATION_LAYER_SESSION_ERROR (3098) indicates a connection drop after a join, often due to packet filtering. ER_GROUP_REPLICATION_MEMBER_BLOCKED (3092) signals quorum loss rather than a join issue.
group_replication_local_address or group_replication_group_seeds lists the wrong IP or port, so peers cannot connect.
Operating system or cloud firewalls block UDP/TCP traffic on ports 33061 or 33062 required by XCom.
Certificates defined in group_replication_ssl_mode or related variables are invalid or inconsistent between nodes.
Nodes run different MySQL versions or mismatched plugin metadata versions, preventing view formation.
DNS or /etc/hosts entries do not resolve peer names, causing timeouts during the join handshake.
The member was expelled from the group after failing to apply transactions within the flow control timeout.
The applier channel could not initialize due to missing privileges or corrupted relay logs.
Communication broke after join, often indicating intermittent network drops or MTU issues.
No. The error affects only the joining node. Existing members continue serving reads and writes if they retain quorum.
Yes. Set group_replication_ssl_mode = 'DISABLED' temporarily, but re enable SSL in production for security.
By default XCom listens on 33061 TCP and UDP. You can change it by editing group_replication_local_address on every node.
Galaxy highlights replication related errors in the query editor output and lets teams share the exact diagnostic SQL, speeding collaboration during incidents.
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