Error 3096 occurs when START GROUP_REPLICATION fails because the group communication layer cannot be initialized.
MySQL Error 3096 ER_GROUP_REPLICATION_COMMUNICATION_LAYER_SESSION_ERROR arises when START GROUP_REPLICATION cannot start the group communication layer, usually due to misconfigured addresses, port conflicts, or firewall blocks. Verify group_replication_* settings, open required ports, and restart the plugin to resolve the problem.
ER_GROUP_REPLICATION_COMMUNICATION_LAYER_SESSION_ERROR
Error 3096 signals that the START GROUP_REPLICATION command could not bring the node online because the Group Communication System (GCS) session failed to start.
The issue appears during group replication bootstrap or when adding a new member. Until fixed, the instance remains outside the replication group, risking data divergence and service downtime.
The GCS layer needs free network ports and consistent configuration across all members. Any mismatch prevents the session from initializing and triggers error 3096.
Other frequent causes include firewalls blocking the group_replication_local_address port, incompatible plugin versions, duplicate server_uuid values, or DNS names that cannot be resolved.
Confirm that the group replication plugin is loaded and all group_replication_* variables are identical on every node except the local address.
Open the required ports (default 33061) on host firewalls and network appliances. Ensure no other service is occupying the port.
When the error appears after a server reboot, check that mysqld auto-loads the plugin before START GROUP_REPLICATION runs in init-file scripts.
When onboarding a new node, verify its server_id and server_uuid differ from existing members, and its view_id is reset by running RESET PERSIST before joining.
Use consistent my.cnf templates managed in version control. Automate validation of group_replication_* parameters during CI/CD deployment steps.
Monitor MySQL error logs for early warnings like "XCom TCP connection failed" so you can act before 3096 prevents replication.
Error 3092 (ER_GROUP_REPLICATION_RESTART_GROUP) indicates an attempt to start replication on an already running group. Stop replication first, then restart.
Error 3098 (ER_GROUP_REPLICATION_COMMAND_FAILURE) covers generic failures inside the group replication plugin. Review the accompanying SQL state for root causes.
Port 33061 blocked by firewall or in use by another service, preventing GCS handshake.
Incorrect group_replication_local_address or group_replication_group_seeds, leading to unreachable peers.
Mismatched plugin versions or disabled group replication plugin on startup.
Duplicate server_uuid or server_id values across group members.
DNS or /etc/hosts misconfiguration that stops hostnames resolving to correct IPs.
Occurs when START GROUP_REPLICATION runs on a node already part of an active group.
Signals a generic failure inside the group replication plugin, often due to wrong GCS configuration.
Raised when mandatory group_replication variables are missing or invalid.
No - it is usually a configuration or networking issue that stops the group communication layer from starting.
Error 3096 exists from MySQL 5.7.6 onward, including 8.0.x releases.
No - the node will not join the group, so ignoring the error risks data inconsistency.
Galaxy's AI copilot validates group_replication settings before deployment and highlights port conflicts, reducing the chance of hitting error 3096.
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