MySQL raises error 3093 ER_GROUP_REPLICATION_RUNNING when START GROUP_REPLICATION is executed on a server where the Group Replication plugin is already active.
MySQL error 3093 ER_GROUP_REPLICATION_RUNNING appears when you issue START GROUP_REPLICATION on a node that is already part of an active replication group. Verify @@group_replication_running, stop the plugin if needed, then restart it once to resolve the issue.
ER_GROUP_REPLICATION_RUNNING
MySQL raises error 3093 ER_GROUP_REPLICATION_RUNNING when you issue START GROUP_REPLICATION against a server that already belongs to an active replication group. The command aborts because MySQL prevents double starting the Group Replication plugin.
The error first appeared in MySQL 5.7.6 and continues in 8.x. It signals a logic or orchestration problem, not a low level engine fault. Resolving it is important because duplicate start attempts can hide real membership issues and delay cluster recovery.
Issuing START GROUP_REPLICATION on a node where group_replication_running remains ON always triggers the error. This often happens in automation scripts that retry starts blindly.
Mismatched configuration, such as auto_start_on_reboot combined with a manual start step, also leads to the duplicate start command. Finally, forgetting to run STOP GROUP_REPLICATION after testing keeps the plugin active and causes future start failures.
First verify the current plugin state. If replication is already running, skip the start command. If it should be restarted, stop it cleanly, then start again.
Always inspect performance_schema and error logs to ensure membership is healthy before restarting. Use idempotent scripts that check @@group_replication_running to avoid repeats.
During cluster boot, an Ansible playbook executes START GROUP_REPLICATION twice. Add a guard clause that checks the running status before issuing the command.
After a crash, an administrator mistakenly starts replication on the primary twice. Use STOP GROUP_REPLICATION to reset, then START GROUP_REPLICATION once.
Write orchestration scripts to evaluate SELECT @@group_replication_running. Only run START GROUP_REPLICATION when the variable returns 0.
Enable autostart in my.cnf or handle manual starts, but not both. Document your procedure so on-call staff follow a single method. Galaxy's AI copilot can inject these checks automatically, preventing duplicate starts.
Error 3092 ER_GROUP_REPLICATION_MAX_GROUP_SIZE is raised when group size exceeds the configured maximum. Reduce instances or adjust group_replication_member_expelled_threshold.
Error 3090 ER_GROUP_REPLICATION_COMMUNICATION_FAILURE signals connectivity problems between group members. Check firewall and group_replication_local_address settings.
Running START GROUP_REPLICATION on a node whose group_replication_running is already 1 triggers the error.
Deployment tools that retry commands without state checks cause duplicate start attempts.
Having auto_start_on_reboot=ON while also calling START GROUP_REPLICATION in init scripts duplicates the action.
Forgetting to stop Group Replication after a test keeps it active and causes future starts to fail.
Indicates that nodes cannot communicate over the group replication transport layer.
Occurs when the applier thread fails to initialize during group replication startup.
The server could not be gracefully removed from the replication group.
Raised when attempting an operation that is incompatible with group replication state.
If replication is already active and healthy, you can ignore the error. Otherwise stop and restart to ensure clean state.
No. It only blocks a redundant start command. Existing replication continues unaffected.
Run SELECT @@group_replication_running or query performance_schema.replication_group_members.
Galaxy's SQL snippets and AI copilot can insert idempotent checks automatically, reducing the chance of duplicate START commands.
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