Merge branch 'master' into master

doc/interactive-commands.md

@@ -38,6 +38,10 @@ Both interfaces may serve at the same time. Both respond to simple text command,
 - `unpostpone`: at a time where `gh-ost` is postponing the [cut-over](cut-over.md) phase, instruct `gh-ost` to stop postponing and proceed immediately to cut-over.
 - `panic`: immediately panic and abort operation
 
+### Querying for data
+
+For commands that accept an argumetn as value, pass `?` (question mark) to _get_ current value rather than _set_ a new one.
+
 ### Examples
 
 While migration is running:
@@ -63,6 +67,11 @@ $ echo "chunk-size=250" | nc -U /tmp/gh-ost.test.sample_data_0.sock
 # Serving on TCP port: 10001
 ```
 
+```shell
+$ echo "chunk-size=?" | nc -U /tmp/gh-ost.test.sample_data_0.sock
+250
+```
+
 ```shell
 $ echo throttle | nc -U /tmp/gh-ost.test.sample_data_0.sock
 

go/base/context.go

@@ -561,7 +561,11 @@ func (this *MigrationContext) GetControlReplicasLagResult() mysql.ReplicationLag
 func (this *MigrationContext) SetControlReplicasLagResult(lagResult *mysql.ReplicationLagResult) {
 	this.throttleMutex.Lock()
 	defer this.throttleMutex.Unlock()
-	this.controlReplicasLagResult = *lagResult
+	if lagResult == nil {
+		this.controlReplicasLagResult = *mysql.NewNoReplicationLagResult()
+	} else {
+		this.controlReplicasLagResult = *lagResult
+	}
 }
 
 func (this *MigrationContext) GetThrottleControlReplicaKeys() *mysql.InstanceKeyMap {

go/logic/migrator.go

@@ -761,6 +761,12 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 			throttleQuery,
 		))
 	}
+	if throttleControlReplicaKeys := this.migrationContext.GetThrottleControlReplicaKeys(); throttleControlReplicaKeys.Len() > 0 {
+		fmt.Fprintln(w, fmt.Sprintf("# throttle-control-replicas count: %+v",
+			throttleControlReplicaKeys.Len(),
+		))
+	}
+
 	if this.migrationContext.PostponeCutOverFlagFile != "" {
 		setIndicator := ""
 		if base.FileExists(this.migrationContext.PostponeCutOverFlagFile) {
@@ -940,7 +946,9 @@ func (this *Migrator) initiateThrottler() error {
 
 	go this.throttler.initiateThrottlerCollection(this.firstThrottlingCollected)
 	log.Infof("Waiting for first throttle metrics to be collected")
-	<-this.firstThrottlingCollected
+	<-this.firstThrottlingCollected // replication lag
+	<-this.firstThrottlingCollected // other metrics
+	log.Infof("First throttle metrics collected")
 	go this.throttler.initiateThrottlerChecks()
 
 	return nil

go/logic/server.go

@@ -126,7 +126,7 @@ func (this *Server) applyServerCommand(command string, writer *bufio.Writer) (pr
 	if len(tokens) > 1 {
 		arg = strings.TrimSpace(tokens[1])
 	}
-
+	argIsQuestion := (arg == "?")
 	throttleHint := "# Note: you may only throttle for as long as your binary logs are not purged\n"
 
 	if err := this.hooksExecutor.onInteractiveCommand(command); err != nil {
@@ -152,6 +152,7 @@ no-throttle                          # End forced throttling (other throttling m
 unpostpone                           # Bail out a cut-over postpone; proceed to cut-over
 panic                                # panic and quit without cleanup
 help                                 # This message
+- use '?' (question mark) as argument to get info rather than set. e.g. "max-load=?" will just print out current max-load.
 `)
 		}
 	case "sup":
@@ -160,6 +161,10 @@ help                                 # This message
 		return ForcePrintStatusAndHintRule, nil
 	case "chunk-size":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", atomic.LoadInt64(&this.migrationContext.ChunkSize))
+				return NoPrintStatusRule, nil
+			}
 			if chunkSize, err := strconv.Atoi(arg); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -169,6 +174,10 @@ help                                 # This message
 		}
 	case "max-lag-millis":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold))
+				return NoPrintStatusRule, nil
+			}
 			if maxLagMillis, err := strconv.Atoi(arg); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -182,6 +191,10 @@ help                                 # This message
 		}
 	case "nice-ratio":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", this.migrationContext.GetNiceRatio())
+				return NoPrintStatusRule, nil
+			}
 			if niceRatio, err := strconv.ParseFloat(arg, 64); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -191,6 +204,11 @@ help                                 # This message
 		}
 	case "max-load":
 		{
+			if argIsQuestion {
+				maxLoad := this.migrationContext.GetMaxLoad()
+				fmt.Fprintf(writer, "%s\n", maxLoad.String())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadMaxLoad(arg); err != nil {
 				return NoPrintStatusRule, err
 			}
@@ -198,6 +216,11 @@ help                                 # This message
 		}
 	case "critical-load":
 		{
+			if argIsQuestion {
+				criticalLoad := this.migrationContext.GetCriticalLoad()
+				fmt.Fprintf(writer, "%s\n", criticalLoad.String())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadCriticalLoad(arg); err != nil {
 				return NoPrintStatusRule, err
 			}
@@ -205,12 +228,20 @@ help                                 # This message
 		}
 	case "throttle-query":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", this.migrationContext.GetThrottleQuery())
+				return NoPrintStatusRule, nil
+			}
 			this.migrationContext.SetThrottleQuery(arg)
 			fmt.Fprintf(writer, throttleHint)
 			return ForcePrintStatusAndHintRule, nil
 		}
 	case "throttle-control-replicas":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%s\n", this.migrationContext.GetThrottleControlReplicaKeys().ToCommaDelimitedList())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadThrottleControlReplicaKeys(arg); err != nil {
 				return NoPrintStatusRule, err
 			}

go/logic/throttler.go

@@ -85,32 +85,37 @@ func (this *Throttler) parseChangelogHeartbeat(heartbeatValue string) (err error
 }
 
 // collectReplicationLag reads the latest changelog heartbeat value
-func (this *Throttler) collectReplicationLag() {
+func (this *Throttler) collectReplicationLag(firstThrottlingCollected chan<- bool) {
+	collectFunc := func() error {
+		if atomic.LoadInt64(&this.migrationContext.CleanupImminentFlag) > 0 {
+			return nil
+		}
+
+		if this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica {
+			// when running on replica, the heartbeat injection is also done on the replica.
+			// This means we will always get a good heartbeat value.
+			// When runnign on replica, we should instead check the `SHOW SLAVE STATUS` output.
+			if lag, err := mysql.GetReplicationLag(this.inspector.connectionConfig); err != nil {
+				return log.Errore(err)
+			} else {
+				atomic.StoreInt64(&this.migrationContext.CurrentLag, int64(lag))
+			}
+		} else {
+			if heartbeatValue, err := this.inspector.readChangelogState("heartbeat"); err != nil {
+				return log.Errore(err)
+			} else {
+				this.parseChangelogHeartbeat(heartbeatValue)
+			}
+		}
+		return nil
+	}
+
+	collectFunc()
+	firstThrottlingCollected <- true
+
 	ticker := time.Tick(time.Duration(this.migrationContext.HeartbeatIntervalMilliseconds) * time.Millisecond)
 	for range ticker {
-		go func() error {
+		go collectFunc()
-			if atomic.LoadInt64(&this.migrationContext.CleanupImminentFlag) > 0 {
-				return nil
-			}
-
-			if this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica {
-				// when running on replica, the heartbeat injection is also done on the replica.
-				// This means we will always get a good heartbeat value.
-				// When runnign on replica, we should instead check the `SHOW SLAVE STATUS` output.
-				if lag, err := mysql.GetReplicationLag(this.inspector.connectionConfig); err != nil {
-					return log.Errore(err)
-				} else {
-					atomic.StoreInt64(&this.migrationContext.CurrentLag, int64(lag))
-				}
-			} else {
-				if heartbeatValue, err := this.inspector.readChangelogState("heartbeat"); err != nil {
-					return log.Errore(err)
-				} else {
-					this.parseChangelogHeartbeat(heartbeatValue)
-				}
-			}
-			return nil
-		}()
 	}
 }
 
@@ -171,9 +176,7 @@ func (this *Throttler) collectControlReplicasLag() {
 			// No need to read lag
 			return
 		}
-		if result := readControlReplicasLag(); result != nil {
+		this.migrationContext.SetControlReplicasLagResult(readControlReplicasLag())
-			this.migrationContext.SetControlReplicasLagResult(result)
-		}
 	}
 	aggressiveTicker := time.Tick(100 * time.Millisecond)
 	relaxedFactor := 10
@@ -285,13 +288,14 @@ func (this *Throttler) collectGeneralThrottleMetrics() error {
 // that may affect throttling. There are several components, all running independently,
 // that collect such metrics.
 func (this *Throttler) initiateThrottlerCollection(firstThrottlingCollected chan<- bool) {
-	go this.collectReplicationLag()
+	go this.collectReplicationLag(firstThrottlingCollected)
 	go this.collectControlReplicasLag()
 
 	go func() {
-		throttlerMetricsTick := time.Tick(1 * time.Second)
 		this.collectGeneralThrottleMetrics()
 		firstThrottlingCollected <- true
+
+		throttlerMetricsTick := time.Tick(1 * time.Second)
 		for range throttlerMetricsTick {
 			this.collectGeneralThrottleMetrics()
 		}

go/mysql/utils.go

@@ -22,6 +22,14 @@ type ReplicationLagResult struct {
 	Err error
 }
 
+func NewNoReplicationLagResult() *ReplicationLagResult {
+	return &ReplicationLagResult{Lag: 0, Err: nil}
+}
+
+func (this *ReplicationLagResult) HasLag() bool {
+	return this.Lag > 0
+}
+
 // GetReplicationLag returns replication lag for a given connection config; either by explicit query
 // or via SHOW SLAVE STATUS
 func GetReplicationLag(connectionConfig *ConnectionConfig) (replicationLag time.Duration, err error) {
@@ -32,9 +40,11 @@ func GetReplicationLag(connectionConfig *ConnectionConfig) (replicationLag time.
 	}
 
 	err = sqlutils.QueryRowsMap(db, `show slave status`, func(m sqlutils.RowMap) error {
+		slaveIORunning := m.GetString("Slave_IO_Running")
+		slaveSQLRunning := m.GetString("Slave_SQL_Running")
 		secondsBehindMaster := m.GetNullInt64("Seconds_Behind_Master")
 		if !secondsBehindMaster.Valid {
-			return fmt.Errorf("replication not running")
+			return fmt.Errorf("replication not running; Slave_IO_Running=%+v, Slave_SQL_Running=%+v", slaveIORunning, slaveSQLRunning)
 		}
 		replicationLag = time.Duration(secondsBehindMaster.Int64) * time.Second
 		return nil

localtests/test.sh

@@ -88,7 +88,7 @@ test_single() {
     --throttle-query='select timestampdiff(second, min(last_update), now()) < 5 from _gh_ost_test_ghc' \
     --serve-socket-file=/tmp/gh-ost.test.sock \
     --initially-drop-socket-file \
-    --postpone-cut-over-flag-file="" \
+    --postpone-cut-over-flag-file=/tmp/gh-ost.test.postpone.flag \
     --test-on-replica \
     --default-retries=1 \
     --verbose \