Merge pull request #1264 from openark/mariadb-gtid-io-thread

Skip RestartReplicationQuick() on MariaDB with GTID

go/logic/topology_recovery.go

@@ -1525,7 +1525,23 @@ func emergentlyRestartReplicationOnTopologyInstance(instanceKey *inst.InstanceKe
 		// Just recently attempted on this specific replica
 		return
 	}
+
 	go inst.ExecuteOnTopology(func() {
+		instance, _, err := inst.ReadInstance(instanceKey)
+		if err != nil {
+			return
+		}
+		if instance.UsingMariaDBGTID {
+			// In MariaDB GTID, stopping and starting IO thread actually deletes relay logs.
+			// This is counter productive to our objective.
+			// Specifically, in a situation where the primary is unreachable and where replicas are lagging,
+			// we want to restart IO thread to see if lag is actually caused by locked primary. If this results
+			// with losing relay logs, then we've lost data.
+			// So, unfortunately we avoid this step in MariaDB GTID.
+			// See https://github.com/openark/orchestrator/issues/1260
+			return
+		}
+
 		inst.RestartReplicationQuick(instanceKey)
 		inst.AuditOperation("emergently-restart-replication-topology-instance", instanceKey, string(analysisCode))
 	})