introducing SkipMaxScaleCheck config

go/config/config.go

@@ -82,6 +82,7 @@ type Configuration struct {
 	BufferInstanceWrites                         bool     // Set to 'true' for write-optimization on backend table (compromise: writes can be stale and overwrite non stale data)
 	InstanceFlushIntervalMilliseconds            int      // Max interval between instance write buffer flushes
 	ReadLongRunningQueries                       bool     // Whether orchestrator should read and record current long running executing queries.
+	SkipMaxScaleCheck                            bool     // If you don't ever have MaxScale BinlogServer in your topology (and most people don't), set this to 'true' to save some pointless queries
 	BinlogFileHistoryDays                        int      // When > 0, amount of days for which orchestrator records per-instance binlog files & sizes
 	UnseenInstanceForgetHours                    uint     // Number of hours after which an unseen instance is forgotten
 	SnapshotTopologiesIntervalHours              uint     // Interval in hour between snapshot-topologies invocation. Default: 0 (disabled)
@@ -253,6 +254,7 @@ func newConfiguration() *Configuration {
 		BufferInstanceWrites:                         false,
 		InstanceFlushIntervalMilliseconds:            100,
 		ReadLongRunningQueries:                       true,
+		SkipMaxScaleCheck:                            false,
 		BinlogFileHistoryDays:                        0,
 		UnseenInstanceForgetHours:                    240,
 		SnapshotTopologiesIntervalHours:              0,

go/inst/instance_dao.go

@@ -150,12 +150,10 @@ func unrecoverableError(err error) bool {
 
 // Check if the instance is a MaxScale binlog server (a proxy not a real
 // MySQL server) and also update the resolved hostname
-func (instance *Instance) checkMaxScale(db *sql.DB, latency *stopwatch.NamedStopwatch) (bool, string, error) {
-	var (
-		err              error
-		isMaxScale       bool
-		resolvedHostname string
-	)
+func (instance *Instance) checkMaxScale(db *sql.DB, latency *stopwatch.NamedStopwatch) (isMaxScale bool, resolvedHostname string, err error) {
+	if config.Config.SkipMaxScaleCheck {
+		return isMaxScale, resolvedHostname, err
+	}
 
 	latency.Start("instance")
 	err = sqlutils.QueryRowsMap(db, "show variables like 'maxscale%'", func(m sqlutils.RowMap) error {