max-lag-millis is dynamicly controllable

Author: Shlomi Noach

build.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 #
 #
-RELEASE_VERSION="1.0.1"
+RELEASE_VERSION="1.0.2"
 
 buildpath=/tmp/gh-ost
 target=gh-ost

doc/interactive-commands.md

@@ -18,6 +18,7 @@ Both interfaces may serve at the same time. Both respond to simple text command,
 - `status`: returns a status summary of migration progress and configuration
 replication lag on to determine throttling
 - `chunk-size=<newsize>`: modify the `chunk-size`; applies on next running copy-iteration
+- `max-lag-millis=<max-lag>`: modify the maximum replication lag threshold (milliseconds, minimum value is `1000`, i.e. 1 second)
 - `max-load=<max-load-thresholds>`: modify the `max-load` config; applies on next running copy-iteration
   The `max-load` format must be: `some_status=<numeric-threshold>[,some_status=<numeric-threshold>...]`. For example: `Threads_running=50,threads_connected=1000`, and you would then write/echo `max-load=Threads_running=50,threads_connected=1000` to the socket.
 - `critical-load=<load>`: change critical load setting (exceeding given thresholds causes panic and abort)

go/base/context.go

@@ -148,7 +148,7 @@ func newMigrationContext() *MigrationContext {
 		ChunkSize:                           1000,
 		InspectorConnectionConfig:           mysql.NewConnectionConfig(),
 		ApplierConnectionConfig:             mysql.NewConnectionConfig(),
-		MaxLagMillisecondsThrottleThreshold: 1000,
+		MaxLagMillisecondsThrottleThreshold: 1500,
 		CutOverLockTimeoutSeconds:           3,
 		maxLoad:                             NewLoadMap(),
 		criticalLoad:                        NewLoadMap(),
@@ -298,6 +298,13 @@ func (this *MigrationContext) TimeSincePointOfInterest() time.Duration {
 	return time.Now().Sub(this.pointOfInterestTime)
 }
 
+func (this *MigrationContext) SetMaxLagMillisecondsThrottleThreshold(maxLagMillisecondsThrottleThreshold int64) {
+	if maxLagMillisecondsThrottleThreshold < 1000 {
+		maxLagMillisecondsThrottleThreshold = 1000
+	}
+	atomic.StoreInt64(&this.MaxLagMillisecondsThrottleThreshold, maxLagMillisecondsThrottleThreshold)
+}
+
 func (this *MigrationContext) SetChunkSize(chunkSize int64) {
 	if chunkSize < 100 {
 		chunkSize = 100

go/cmd/gh-ost/main.go

@@ -74,7 +74,7 @@ func main() {
 	cutOverLockTimeoutSeconds := flag.Int64("cut-over-lock-timeout-seconds", 3, "Max number of seconds to hold locks on tables while attempting to cut-over (retry attempted when lock exceeds timeout)")
 	flag.Int64Var(&migrationContext.NiceRatio, "nice-ratio", 0, "force being 'nice', imply sleep time per chunk time. Example values: 0 is aggressive. 3: for every ms spend in a rowcopy chunk, spend 3ms sleeping immediately after")
 
-	flag.Int64Var(&migrationContext.MaxLagMillisecondsThrottleThreshold, "max-lag-millis", 1500, "replication lag at which to throttle operation")
+	maxLagMillis := flag.Int64("max-lag-millis", 1500, "replication lag at which to throttle operation")
 	flag.StringVar(&migrationContext.ReplictionLagQuery, "replication-lag-query", "", "Query that detects replication lag in seconds. Result can be a floating point (by default gh-ost issues SHOW SLAVE STATUS and reads Seconds_behind_master). If you're using pt-heartbeat, query would be something like: SELECT ROUND(UNIX_TIMESTAMP() - MAX(UNIX_TIMESTAMP(ts))) AS delay FROM my_schema.heartbeat")
 	throttleControlReplicas := flag.String("throttle-control-replicas", "", "List of replicas on which to check for lag; comma delimited. Example: myhost1.com:3306,myhost2.com,myhost3.com:3307")
 	flag.StringVar(&migrationContext.ThrottleQuery, "throttle-query", "", "when given, issued (every second) to check if operation should throttle. Expecting to return zero for no-throttle, >0 for throttle. Query is issued on the migrated server. Make sure this query is lightweight")
@@ -171,6 +171,7 @@ func main() {
 		migrationContext.ServeSocketFile = fmt.Sprintf("/tmp/gh-ost.%s.%s.sock", migrationContext.DatabaseName, migrationContext.OriginalTableName)
 	}
 	migrationContext.SetChunkSize(*chunkSize)
+	migrationContext.SetMaxLagMillisecondsThrottleThreshold(*maxLagMillis)
 	migrationContext.SetDefaultNumRetries(*defaultRetries)
 	migrationContext.ApplyCredentials()
 	if err := migrationContext.SetCutOverLockTimeoutSeconds(*cutOverLockTimeoutSeconds); err != nil {

go/logic/migrator.go

@@ -148,16 +148,17 @@ func (this *Migrator) shouldThrottle() (result bool, reason string) {
 		}
 	}
 	// Replication lag throttle
+	maxLagMillisecondsThrottleThreshold := atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold)
 	lag := atomic.LoadInt64(&this.migrationContext.CurrentLag)
-	if time.Duration(lag) > time.Duration(this.migrationContext.MaxLagMillisecondsThrottleThreshold)*time.Millisecond {
+	if time.Duration(lag) > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
 		return true, fmt.Sprintf("lag=%fs", time.Duration(lag).Seconds())
 	}
 	if (this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica) && (atomic.LoadInt64(&this.allEventsUpToLockProcessedInjectedFlag) == 0) {
 		replicationLag, err := mysql.GetMaxReplicationLag(this.migrationContext.InspectorConnectionConfig, this.migrationContext.ThrottleControlReplicaKeys, this.migrationContext.ReplictionLagQuery)
 		if err != nil {
 			return true, err.Error()
 		}
-		if replicationLag > time.Duration(this.migrationContext.MaxLagMillisecondsThrottleThreshold)*time.Millisecond {
+		if replicationLag > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
 			return true, fmt.Sprintf("replica-lag=%fs", replicationLag.Seconds())
 		}
 	}
@@ -792,6 +793,7 @@ status                               # Print a status message
 chunk-size=<newsize>                 # Set a new chunk-size
 nice-ratio=<ratio>                   # Set a new nice-ratio, integer (0 is agrressive)
 critical-load=<load>                 # Set a new set of max-load thresholds
+max-lag-millis=<max-lag>             # Set a new replication lag threshold
 max-load=<load>                      # Set a new set of max-load thresholds
 throttle-query=<query>               # Set a new throttle-query
 throttle-control-replicas=<replicas> #
@@ -814,6 +816,16 @@ help                                 # This message
 				this.printStatus(ForcePrintStatusAndHint, writer)
 			}
 		}
+	case "max-lag-millis":
+		{
+			if maxLagMillis, err := strconv.Atoi(arg); err != nil {
+				fmt.Fprintf(writer, "%s\n", err.Error())
+				return log.Errore(err)
+			} else {
+				this.migrationContext.SetMaxLagMillisecondsThrottleThreshold(int64(maxLagMillis))
+				this.printStatus(ForcePrintStatusAndHint, writer)
+			}
+		}
 	case "nice-ratio":
 		{
 			if niceRatio, err := strconv.Atoi(arg); err != nil {
@@ -974,7 +986,7 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 	))
 	maxLoad := this.migrationContext.GetMaxLoad()
 	criticalLoad := this.migrationContext.GetCriticalLoad()
-	fmt.Fprintln(w, fmt.Sprintf("# chunk-size: %+v; max lag: %+vms; max-load: %s; critical-load: %s; nice-ratio: %d",
+	fmt.Fprintln(w, fmt.Sprintf("# chunk-size: %+v; max-lag-millis: %+vms; max-load: %s; critical-load: %s; nice-ratio: %d",
 		atomic.LoadInt64(&this.migrationContext.ChunkSize),
 		atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold),
 		maxLoad.String(),