Ejemplo n.º 1
0
// findDestinationMasters finds for each destination shard the current master.
func (scw *SplitCloneWorker) findDestinationMasters(ctx context.Context) error {
	scw.setState(WorkerStateFindTargets)

	// Make sure we find a master for each destination shard and log it.
	scw.wr.Logger().Infof("Finding a MASTER tablet for each destination shard...")
	for _, si := range scw.destinationShards {
		waitCtx, waitCancel := context.WithTimeout(ctx, *waitForHealthyTabletsTimeout)
		defer waitCancel()
		if err := discovery.WaitForTablets(waitCtx, scw.healthCheck,
			scw.cell, si.Keyspace(), si.ShardName(), []topodatapb.TabletType{topodatapb.TabletType_MASTER}); err != nil {
			return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v (in cell: %v): %v", si.Keyspace(), si.ShardName(), scw.cell, err)
		}
		masters := discovery.GetCurrentMaster(
			scw.healthCheck.GetTabletStatsFromTarget(si.Keyspace(), si.ShardName(), topodatapb.TabletType_MASTER))
		if len(masters) == 0 {
			return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v (in cell: %v) in HealthCheck: empty TabletStats list", si.Keyspace(), si.ShardName(), scw.cell)
		}
		master := masters[0]

		// Get the MySQL database name of the tablet.
		keyspaceAndShard := topoproto.KeyspaceShardString(si.Keyspace(), si.ShardName())
		scw.destinationDbNames[keyspaceAndShard] = topoproto.TabletDbName(master.Tablet)

		// TODO(mberlin): Verify on the destination master that the
		// _vt.blp_checkpoint table has the latest schema.

		scw.wr.Logger().Infof("Using tablet %v as destination master for %v/%v", topoproto.TabletAliasString(master.Tablet.Alias), si.Keyspace(), si.ShardName())
	}
	scw.wr.Logger().Infof("NOTE: The used master of a destination shard might change over the course of the copy e.g. due to a reparent. The HealthCheck module will track and log master changes and any error message will always refer the actually used master address.")

	return nil
}
Ejemplo n.º 2
0
func waitForHealthyRdonlyTablets(ctx context.Context, wr *wrangler.Wrangler, healthCheck discovery.HealthCheck, cell, keyspace, shard string, minHealthyRdonlyTablets int, timeout time.Duration) ([]*discovery.TabletStats, error) {
	busywaitCtx, busywaitCancel := context.WithTimeout(ctx, timeout)
	defer busywaitCancel()

	start := time.Now()
	deadlineForLog, _ := busywaitCtx.Deadline()
	wr.Logger().Infof("Waiting for enough healthy RDONLY tablets to become available in (%v,%v/%v). required: %v Waiting up to %.1f seconds.",
		cell, keyspace, shard, minHealthyRdonlyTablets, deadlineForLog.Sub(time.Now()).Seconds())

	// Wait for at least one RDONLY tablet initially before checking the list.
	if err := discovery.WaitForTablets(busywaitCtx, healthCheck, cell, keyspace, shard, []topodatapb.TabletType{topodatapb.TabletType_RDONLY}); err != nil {
		return nil, fmt.Errorf("error waiting for RDONLY tablets for (%v,%v/%v): %v", cell, keyspace, shard, err)
	}

	var healthyTablets []*discovery.TabletStats
	for {
		select {
		case <-busywaitCtx.Done():
			return nil, fmt.Errorf("not enough healthy RDONLY tablets to choose from in (%v,%v/%v), have %v healthy ones, need at least %v Context error: %v",
				cell, keyspace, shard, len(healthyTablets), minHealthyRdonlyTablets, busywaitCtx.Err())
		default:
		}

		healthyTablets = discovery.RemoveUnhealthyTablets(
			healthCheck.GetTabletStatsFromTarget(keyspace, shard, topodatapb.TabletType_RDONLY))
		if len(healthyTablets) >= minHealthyRdonlyTablets {
			break
		}

		deadlineForLog, _ := busywaitCtx.Deadline()
		wr.Logger().Infof("Waiting for enough healthy RDONLY tablets to become available (%v,%v/%v). available: %v required: %v Waiting up to %.1f more seconds.",
			cell, keyspace, shard, len(healthyTablets), minHealthyRdonlyTablets, deadlineForLog.Sub(time.Now()).Seconds())
		// Block for 1 second because 2 seconds is the -health_check_interval flag value in integration tests.
		timer := time.NewTimer(1 * time.Second)
		select {
		case <-busywaitCtx.Done():
			timer.Stop()
		case <-timer.C:
		}
	}
	wr.Logger().Infof("At least %v healthy RDONLY tablets are available in (%v,%v/%v) (required: %v). Took %.1f seconds to find this out.",
		len(healthyTablets), cell, keyspace, shard, minHealthyRdonlyTablets, time.Now().Sub(start).Seconds())
	return healthyTablets, nil
}
Ejemplo n.º 3
0
// Iteration is a single iteration for the player: get the current status,
// try to play, and plays until interrupted, or until an error occurs.
func (bpc *BinlogPlayerController) Iteration() (err error) {
	defer func() {
		if x := recover(); x != nil {
			log.Errorf("%v: caught panic: %v\n%s", bpc, x, tb.Stack(4))
			err = fmt.Errorf("panic: %v", x)
		}
	}()

	// Check if the context is still good.
	select {
	case <-bpc.ctx.Done():
		if bpc.ctx.Err() == context.Canceled {
			// We were stopped. Break out of Loop().
			return nil
		}
		return fmt.Errorf("giving up since the context is done: %v", bpc.ctx.Err())
	default:
	}

	// Apply any special settings necessary for playback of binlogs.
	// We do it on every iteration to be sure, in case MySQL was restarted.
	if err := bpc.mysqld.EnableBinlogPlayback(); err != nil {
		// We failed to apply the required settings, so we shouldn't keep going.
		return err
	}

	// create the db connection, connect it
	vtClient := bpc.vtClientFactory()
	if err := vtClient.Connect(); err != nil {
		return fmt.Errorf("can't connect to database: %v", err)
	}
	defer vtClient.Close()

	// Read the start position
	startPosition, flags, err := binlogplayer.ReadStartPosition(vtClient, bpc.sourceShard.Uid)
	if err != nil {
		return fmt.Errorf("can't read startPosition: %v", err)
	}

	// if we shouldn't start, we just error out and try again later
	if strings.Index(flags, binlogplayer.BlpFlagDontStart) != -1 {
		return fmt.Errorf("not starting because flag '%v' is set", binlogplayer.BlpFlagDontStart)
	}

	// wait for the tablet set (usefull for the first run at least, fast for next runs)
	if err := discovery.WaitForTablets(bpc.ctx, bpc.healthCheck, bpc.cell, bpc.sourceShard.Keyspace, bpc.sourceShard.Shard, []topodatapb.TabletType{topodatapb.TabletType_REPLICA}); err != nil {
		return fmt.Errorf("error waiting for tablets for %v %v %v: %v", bpc.cell, bpc.sourceShard.String(), topodatapb.TabletType_REPLICA, err)
	}

	// Find the server list from the health check
	addrs := discovery.RemoveUnhealthyTablets(
		bpc.healthCheck.GetTabletStatsFromTarget(bpc.sourceShard.Keyspace, bpc.sourceShard.Shard, topodatapb.TabletType_REPLICA))
	if len(addrs) == 0 {
		return fmt.Errorf("can't find any healthy source tablet for %v %v %v", bpc.cell, bpc.sourceShard.String(), topodatapb.TabletType_REPLICA)
	}
	newServerIndex := rand.Intn(len(addrs))
	tablet := addrs[newServerIndex].Tablet

	// save our current server
	bpc.playerMutex.Lock()
	bpc.sourceTablet = tablet.Alias
	bpc.lastError = nil
	bpc.playerMutex.Unlock()

	// check which kind of replication we're doing, tables or keyrange
	if len(bpc.sourceShard.Tables) > 0 {
		// tables, first resolve wildcards
		tables, err := mysqlctl.ResolveTables(bpc.mysqld, bpc.dbName, bpc.sourceShard.Tables)
		if err != nil {
			return fmt.Errorf("failed to resolve table names: %v", err)
		}

		// tables, just get them
		player, err := binlogplayer.NewBinlogPlayerTables(vtClient, tablet, tables, bpc.sourceShard.Uid, startPosition, bpc.stopPosition, bpc.binlogPlayerStats)
		if err != nil {
			return fmt.Errorf("NewBinlogPlayerTables failed: %v", err)
		}
		return player.ApplyBinlogEvents(bpc.ctx)
	}
	// the data we have to replicate is the intersection of the
	// source keyrange and our keyrange
	overlap, err := key.KeyRangesOverlap(bpc.sourceShard.KeyRange, bpc.keyRange)
	if err != nil {
		return fmt.Errorf("Source shard %v doesn't overlap destination shard %v", bpc.sourceShard.KeyRange, bpc.keyRange)
	}

	player, err := binlogplayer.NewBinlogPlayerKeyRange(vtClient, tablet, overlap, bpc.sourceShard.Uid, startPosition, bpc.stopPosition, bpc.binlogPlayerStats)
	if err != nil {
		return fmt.Errorf("NewBinlogPlayerKeyRange failed: %v", err)
	}
	return player.ApplyBinlogEvents(bpc.ctx)
}
Ejemplo n.º 4
0
// findTargets phase:
// - find one rdonly in the source shard
// - mark it as 'worker' pointing back to us
// - get the aliases of all the targets
func (vscw *VerticalSplitCloneWorker) findTargets(ctx context.Context) error {
	vscw.setState(WorkerStateFindTargets)

	// find an appropriate tablet in the source shard
	var err error
	vscw.sourceAlias, err = FindWorkerTablet(ctx, vscw.wr, vscw.cleaner, nil /* healthCheck */, vscw.cell, vscw.sourceKeyspace, "0", vscw.minHealthyRdonlyTablets)
	if err != nil {
		return fmt.Errorf("FindWorkerTablet() failed for %v/%v/0: %v", vscw.cell, vscw.sourceKeyspace, err)
	}
	vscw.wr.Logger().Infof("Using tablet %v as the source", topoproto.TabletAliasString(vscw.sourceAlias))

	// get the tablet info for it
	shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
	ti, err := vscw.wr.TopoServer().GetTablet(shortCtx, vscw.sourceAlias)
	cancel()
	if err != nil {
		return fmt.Errorf("cannot read tablet %v: %v", topoproto.TabletAliasString(vscw.sourceAlias), err)
	}
	vscw.sourceTablet = ti.Tablet

	// stop replication on it
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	err = vscw.wr.TabletManagerClient().StopSlave(shortCtx, vscw.sourceTablet)
	cancel()
	if err != nil {
		return fmt.Errorf("cannot stop replication on tablet %v", topoproto.TabletAliasString(vscw.sourceAlias))
	}

	wrangler.RecordStartSlaveAction(vscw.cleaner, vscw.sourceTablet)

	// Initialize healthcheck and add destination shards to it.
	vscw.healthCheck = discovery.NewHealthCheck(*remoteActionsTimeout, *healthcheckRetryDelay, *healthCheckTimeout)
	watcher := discovery.NewShardReplicationWatcher(vscw.wr.TopoServer(), vscw.healthCheck,
		vscw.cell, vscw.destinationKeyspace, vscw.destinationShard,
		*healthCheckTopologyRefresh, discovery.DefaultTopoReadConcurrency)
	vscw.destinationShardWatchers = append(vscw.destinationShardWatchers, watcher)

	// Make sure we find a master for each destination shard and log it.
	vscw.wr.Logger().Infof("Finding a MASTER tablet for each destination shard...")
	waitCtx, waitCancel := context.WithTimeout(ctx, 10*time.Second)
	defer waitCancel()
	if err := discovery.WaitForTablets(waitCtx, vscw.healthCheck,
		vscw.cell, vscw.destinationKeyspace, vscw.destinationShard, []topodatapb.TabletType{topodatapb.TabletType_MASTER}); err != nil {
		return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v: %v", vscw.destinationKeyspace, vscw.destinationShard, err)
	}
	masters := discovery.GetCurrentMaster(
		vscw.healthCheck.GetTabletStatsFromTarget(vscw.destinationKeyspace, vscw.destinationShard, topodatapb.TabletType_MASTER))
	if len(masters) == 0 {
		return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v in HealthCheck: empty TabletStats list", vscw.destinationKeyspace, vscw.destinationShard)
	}
	master := masters[0]

	// Get the MySQL database name of the tablet.
	keyspaceAndShard := topoproto.KeyspaceShardString(vscw.destinationKeyspace, vscw.destinationShard)
	vscw.destinationDbNames[keyspaceAndShard] = topoproto.TabletDbName(master.Tablet)

	// TODO(mberlin): Verify on the destination master that the
	// _vt.blp_checkpoint table has the latest schema.

	vscw.wr.Logger().Infof("Using tablet %v as destination master for %v/%v", topoproto.TabletAliasString(master.Tablet.Alias), vscw.destinationKeyspace, vscw.destinationShard)
	vscw.wr.Logger().Infof("NOTE: The used master of a destination shard might change over the course of the copy e.g. due to a reparent. The HealthCheck module will track and log master changes and any error message will always refer the actually used master address.")

	return nil
}
Ejemplo n.º 5
0
func (wr *Wrangler) waitForDrainInCell(ctx context.Context, cell, keyspace, shard string, servedType topodatapb.TabletType,
	retryDelay, healthCheckTopologyRefresh, healthcheckRetryDelay, healthCheckTimeout time.Duration) error {
	hc := discovery.NewHealthCheck(healthCheckTimeout /* connectTimeout */, healthcheckRetryDelay, healthCheckTimeout)
	defer hc.Close()
	watcher := discovery.NewShardReplicationWatcher(wr.TopoServer(), hc, cell, keyspace, shard, healthCheckTopologyRefresh, discovery.DefaultTopoReadConcurrency)
	defer watcher.Stop()

	if err := discovery.WaitForTablets(ctx, hc, cell, keyspace, shard, []topodatapb.TabletType{servedType}); err != nil {
		return fmt.Errorf("%v: error waiting for initial %v tablets for %v/%v: %v", cell, servedType, keyspace, shard, err)
	}

	wr.Logger().Infof("%v: Waiting for %.1f seconds to make sure that the discovery module retrieves healthcheck information from all tablets.",
		cell, healthCheckTimeout.Seconds())
	// Wait at least for -vtctl_healthcheck_timeout to elapse to make sure that we
	// see all healthy tablets. Otherwise, we might miss some tablets.
	// It's safe to wait not longer for this because we would only miss slow
	// tablets and vtgate would not serve from such tablets anyway.
	time.Sleep(healthCheckTimeout)

	// Now check the QPS rate of all tablets until the timeout expires.
	startTime := time.Now()
	for {
		// map key: tablet uid
		drainedHealthyTablets := make(map[uint32]*discovery.TabletStats)
		notDrainedHealtyTablets := make(map[uint32]*discovery.TabletStats)

		healthyTablets := discovery.RemoveUnhealthyTablets(
			hc.GetTabletStatsFromTarget(keyspace, shard, servedType))
		for _, ts := range healthyTablets {
			if ts.Stats.Qps == 0.0 {
				drainedHealthyTablets[ts.Tablet.Alias.Uid] = ts
			} else {
				notDrainedHealtyTablets[ts.Tablet.Alias.Uid] = ts
			}
		}

		if len(drainedHealthyTablets) == len(healthyTablets) {
			wr.Logger().Infof("%v: All %d healthy tablets were drained after %.1f seconds (not counting %.1f seconds for the initial wait).",
				cell, len(healthyTablets), time.Now().Sub(startTime).Seconds(), healthCheckTimeout.Seconds())
			break
		}

		// Continue waiting, sleep in between.
		deadlineString := ""
		if d, ok := ctx.Deadline(); ok {
			deadlineString = fmt.Sprintf(" up to %.1f more seconds", d.Sub(time.Now()).Seconds())
		}
		wr.Logger().Infof("%v: Waiting%v for all healthy tablets to be drained (%d/%d done).",
			cell, deadlineString, len(drainedHealthyTablets), len(healthyTablets))

		timer := time.NewTimer(retryDelay)
		select {
		case <-ctx.Done():
			timer.Stop()

			var l []string
			for _, ts := range notDrainedHealtyTablets {
				l = append(l, formatTabletStats(ts))
			}
			return fmt.Errorf("%v: WaitForDrain failed for %v tablets in %v/%v. Only %d/%d tablets were drained. err: %v List of tablets which were not drained: %v",
				cell, servedType, keyspace, shard, len(drainedHealthyTablets), len(healthyTablets), ctx.Err(), strings.Join(l, ";"))
		case <-timer.C:
		}
	}

	return nil
}
Ejemplo n.º 6
0
// findTargets phase:
// - find one rdonly in the source shard
// - mark it as 'worker' pointing back to us
// - get the aliases of all the targets
func (scw *LegacySplitCloneWorker) findTargets(ctx context.Context) error {
	scw.setState(WorkerStateFindTargets)
	var err error

	// find an appropriate tablet in the source shards
	scw.sourceAliases = make([]*topodatapb.TabletAlias, len(scw.sourceShards))
	for i, si := range scw.sourceShards {
		scw.sourceAliases[i], err = FindWorkerTablet(ctx, scw.wr, scw.cleaner, scw.healthCheck, scw.cell, si.Keyspace(), si.ShardName(), scw.minHealthyRdonlyTablets)
		if err != nil {
			return fmt.Errorf("FindWorkerTablet() failed for %v/%v/%v: %v", scw.cell, si.Keyspace(), si.ShardName(), err)
		}
		scw.wr.Logger().Infof("Using tablet %v as source for %v/%v", topoproto.TabletAliasString(scw.sourceAliases[i]), si.Keyspace(), si.ShardName())
	}

	// get the tablet info for them, and stop their replication
	scw.sourceTablets = make([]*topodatapb.Tablet, len(scw.sourceAliases))
	for i, alias := range scw.sourceAliases {
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		ti, err := scw.wr.TopoServer().GetTablet(shortCtx, alias)
		cancel()
		if err != nil {
			return fmt.Errorf("cannot read tablet %v: %v", topoproto.TabletAliasString(alias), err)
		}
		scw.sourceTablets[i] = ti.Tablet

		shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
		err = scw.wr.TabletManagerClient().StopSlave(shortCtx, scw.sourceTablets[i])
		cancel()
		if err != nil {
			return fmt.Errorf("cannot stop replication on tablet %v", topoproto.TabletAliasString(alias))
		}

		wrangler.RecordStartSlaveAction(scw.cleaner, scw.sourceTablets[i])
	}

	// Initialize healthcheck and add destination shards to it.
	scw.healthCheck = discovery.NewHealthCheck(*remoteActionsTimeout, *healthcheckRetryDelay, *healthCheckTimeout)
	for _, si := range scw.destinationShards {
		watcher := discovery.NewShardReplicationWatcher(scw.wr.TopoServer(), scw.healthCheck,
			scw.cell, si.Keyspace(), si.ShardName(),
			*healthCheckTopologyRefresh, discovery.DefaultTopoReadConcurrency)
		scw.destinationShardWatchers = append(scw.destinationShardWatchers, watcher)
	}

	// Make sure we find a master for each destination shard and log it.
	scw.wr.Logger().Infof("Finding a MASTER tablet for each destination shard...")
	for _, si := range scw.destinationShards {
		waitCtx, waitCancel := context.WithTimeout(ctx, 10*time.Second)
		defer waitCancel()
		if err := discovery.WaitForTablets(waitCtx, scw.healthCheck,
			scw.cell, si.Keyspace(), si.ShardName(), []topodatapb.TabletType{topodatapb.TabletType_MASTER}); err != nil {
			return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v: %v", si.Keyspace(), si.ShardName(), err)
		}
		masters := discovery.GetCurrentMaster(
			scw.healthCheck.GetTabletStatsFromTarget(si.Keyspace(), si.ShardName(), topodatapb.TabletType_MASTER))
		if len(masters) == 0 {
			return fmt.Errorf("cannot find MASTER tablet for destination shard for %v/%v in HealthCheck: empty TabletStats list", si.Keyspace(), si.ShardName())
		}
		master := masters[0]

		// Get the MySQL database name of the tablet.
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		ti, err := scw.wr.TopoServer().GetTablet(shortCtx, master.Tablet.Alias)
		cancel()
		if err != nil {
			return fmt.Errorf("cannot get the TabletInfo for destination master (%v) to find out its db name: %v", topoproto.TabletAliasString(master.Tablet.Alias), err)
		}
		keyspaceAndShard := topoproto.KeyspaceShardString(si.Keyspace(), si.ShardName())
		scw.destinationDbNames[keyspaceAndShard] = ti.DbName()

		// TODO(mberlin): Verify on the destination master that the
		// _vt.blp_checkpoint table has the latest schema.

		scw.wr.Logger().Infof("Using tablet %v as destination master for %v/%v", topoproto.TabletAliasString(master.Tablet.Alias), si.Keyspace(), si.ShardName())
	}
	scw.wr.Logger().Infof("NOTE: The used master of a destination shard might change over the course of the copy e.g. due to a reparent. The HealthCheck module will track and log master changes and any error message will always refer the actually used master address.")

	// Set up the throttler for each destination shard.
	for _, si := range scw.destinationShards {
		keyspaceAndShard := topoproto.KeyspaceShardString(si.Keyspace(), si.ShardName())
		t, err := throttler.NewThrottler(
			keyspaceAndShard, "transactions", scw.destinationWriterCount, scw.maxTPS, throttler.ReplicationLagModuleDisabled)
		if err != nil {
			return fmt.Errorf("cannot instantiate throttler: %v", err)
		}
		scw.destinationThrottlers[keyspaceAndShard] = t
	}

	return nil
}
Ejemplo n.º 7
0
// TestRealtimeStatsWithQueryService uses fakeTablets and the fakeQueryService to
// copy the environment needed for the HealthCheck object.
func TestRealtimeStatsWithQueryService(t *testing.T) {
	// Set up testing keyspace with 2 tablets within 2 cells.
	keyspace := "ks"
	shard := "-80"
	tabletType := topodatapb.TabletType_REPLICA.String()
	ctx := context.Background()
	db := fakesqldb.Register()
	ts := zktestserver.New(t, []string{"cell1", "cell2"})
	wr := wrangler.New(logutil.NewConsoleLogger(), ts, tmclient.NewTabletManagerClient())

	if err := ts.CreateKeyspace(context.Background(), keyspace, &topodatapb.Keyspace{
		ShardingColumnName: "keyspace_id",
		ShardingColumnType: topodatapb.KeyspaceIdType_UINT64,
	}); err != nil {
		t.Fatalf("CreateKeyspace failed: %v", err)
	}

	t1 := testlib.NewFakeTablet(t, wr, "cell1", 0, topodatapb.TabletType_REPLICA, db,
		testlib.TabletKeyspaceShard(t, keyspace, shard))
	t2 := testlib.NewFakeTablet(t, wr, "cell2", 1, topodatapb.TabletType_REPLICA, db,
		testlib.TabletKeyspaceShard(t, keyspace, shard))
	for _, ft := range []*(testlib.FakeTablet){t1, t2} {
		ft.StartActionLoop(t, wr)
		defer ft.StopActionLoop(t)
	}

	target := querypb.Target{
		Keyspace:   keyspace,
		Shard:      shard,
		TabletType: topodatapb.TabletType_REPLICA,
	}
	fqs1 := fakes.NewStreamHealthQueryService(target)
	fqs2 := fakes.NewStreamHealthQueryService(target)
	grpcqueryservice.Register(t1.RPCServer, fqs1)
	grpcqueryservice.Register(t2.RPCServer, fqs2)

	fqs1.AddDefaultHealthResponse()

	realtimeStats, err := newRealtimeStats(ts)
	if err != nil {
		t.Fatalf("newRealtimeStats error: %v", err)
	}

	if err := discovery.WaitForTablets(ctx, realtimeStats.healthCheck, "cell1", keyspace, shard, []topodatapb.TabletType{topodatapb.TabletType_REPLICA}); err != nil {
		t.Fatalf("waitForTablets failed: %v", err)
	}

	// Test 1: tablet1's stats should be updated with the one received by the HealthCheck object.
	result := realtimeStats.tabletStatuses("cell1", keyspace, shard, tabletType)
	got := result["0"].Stats
	want := &querypb.RealtimeStats{
		SecondsBehindMaster: 1,
	}
	if !proto.Equal(got, want) {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// Test 2: tablet1's stats should be updated with the new one received by the HealthCheck object.
	fqs1.AddHealthResponseWithQPS(2.0)
	want2 := &querypb.RealtimeStats{
		SecondsBehindMaster: 1,
		Qps:                 2.0,
	}
	if err := checkStats(realtimeStats, "0", "cell1", keyspace, shard, tabletType, want2); err != nil {
		t.Errorf("%v", err)
	}

	// Test 3: tablet2's stats should be updated with the one received by the HealthCheck object,
	// leaving tablet1's stats unchanged.
	fqs2.AddHealthResponseWithQPS(3.0)
	want3 := &querypb.RealtimeStats{
		SecondsBehindMaster: 1,
		Qps:                 3.0,
	}
	if err := checkStats(realtimeStats, "1", "cell2", keyspace, shard, tabletType, want3); err != nil {
		t.Errorf("%v", err)
	}

	if err := checkStats(realtimeStats, "0", "cell1", keyspace, shard, tabletType, want2); err != nil {
		t.Errorf("%v", err)
	}
}