Heartbeat writer can always generate on-demand leased heartbeats, even if not at all configured

go/timer/rate_limiter.go

@@ -77,6 +77,14 @@ func (r *RateLimiter) DoEmpty() {
 	_ = r.Do(nil)
 }
 
+// AllowOne allows the next Do() call to run, even if the rate limiter would otherwise skip it.
+func (r *RateLimiter) AllowOne() {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	r.lastDoValue = r.tickerValue.Load() - 1
+}
+
 // Diff returns the logical clock diff between the ticker and the last Do() call.
 func (r *RateLimiter) Diff() int64 {
 	r.mu.Lock()
@@ -87,7 +95,9 @@ func (r *RateLimiter) Diff() int64 {
 
 // Stop terminates rate limiter's operation and will not allow any more Do() executions.
 func (r *RateLimiter) Stop() {
-	r.cancel()
+	if r.cancel != nil {
+		r.cancel()
+	}
 
 	r.mu.Lock()
 	defer r.mu.Unlock()

go/timer/rate_limiter_test.go

@@ -54,6 +54,23 @@ func TestRateLimiterShort(t *testing.T) {
 	assert.Less(t, val, 10)
 }
 
+func TestRateLimiterAllowOne(t *testing.T) {
+	r := NewRateLimiter(time.Millisecond * 250)
+	require.NotNil(t, r)
+	defer r.Stop()
+	val := 0
+	incr := func() error { val++; return nil }
+	times := 10
+	for range times {
+		time.Sleep(time.Millisecond * 100)
+		r.AllowOne()
+		err := r.Do(incr)
+		assert.NoError(t, err)
+	}
+	// we expect exactly 10 successful entries.
+	assert.Equal(t, times, val)
+}
+
 func TestRateLimiterStop(t *testing.T) {
 	r := NewRateLimiter(time.Millisecond * 10)
 	require.NotNil(t, r)
@@ -91,3 +108,8 @@ func TestRateLimiterDiff(t *testing.T) {
 	r.DoEmpty()
 	assert.LessOrEqual(t, r.Diff(), int64(1))
 }
+
+func TestRateLimiterUninitialized(t *testing.T) {
+	r := &RateLimiter{}
+	r.Stop()
+}

go/vt/vttablet/tabletserver/repltracker/repltracker.go

@@ -52,8 +52,7 @@ var (
 
 // ReplTracker tracks replication lag.
 type ReplTracker struct {
-	mode           string
-	forceHeartbeat bool
+	mode string
 
 	mu        sync.Mutex
 	isPrimary bool
@@ -66,11 +65,10 @@ type ReplTracker struct {
 // NewReplTracker creates a new ReplTracker.
 func NewReplTracker(env tabletenv.Env, alias *topodatapb.TabletAlias) *ReplTracker {
 	return &ReplTracker{
-		mode:           env.Config().ReplicationTracker.Mode,
-		forceHeartbeat: env.Config().ReplicationTracker.HeartbeatOnDemand > 0,
-		hw:             newHeartbeatWriter(env, alias),
-		hr:             newHeartbeatReader(env),
-		poller:         &poller{},
+		mode:   env.Config().ReplicationTracker.Mode,
+		hw:     newHeartbeatWriter(env, alias),
+		hr:     newHeartbeatReader(env),
+		poller: &poller{},
 	}
 }
 
@@ -97,9 +95,7 @@ func (rt *ReplTracker) MakePrimary() {
 		rt.hr.Close()
 		rt.hw.Open()
 	}
-	if rt.forceHeartbeat {
-		rt.hw.Open()
-	}
+	rt.hw.Open()
 }
 
 // MakeNonPrimary must be called if the tablet type becomes non-PRIMARY.
@@ -117,9 +113,7 @@ func (rt *ReplTracker) MakeNonPrimary() {
 		// Run the status once to pre-initialize values.
 		rt.poller.Status()
 	}
-	if rt.forceHeartbeat {
-		rt.hw.Close()
-	}
+	rt.hw.Close()
 }
 
 // Close closes ReplTracker.
@@ -147,5 +141,9 @@ func (rt *ReplTracker) Status() (time.Duration, error) {
 // EnableHeartbeat enables or disables writes of heartbeat. This functionality
 // is only used by tests.
 func (rt *ReplTracker) EnableHeartbeat(enable bool) {
-	rt.hw.enableWrites(enable)
+	if enable {
+		rt.hw.enableWrites()
+	} else {
+		rt.hw.disableWrites()
+	}
 }

go/vt/vttablet/tabletserver/repltracker/repltracker_test.go

@@ -50,49 +50,91 @@ func TestReplTracker(t *testing.T) {
 	target := &querypb.Target{}
 	mysqld := mysqlctl.NewFakeMysqlDaemon(nil)
 
-	rt := NewReplTracker(env, alias)
-	rt.InitDBConfig(target, mysqld)
-	assert.Equal(t, tabletenv.Heartbeat, rt.mode)
-	assert.True(t, rt.hw.enabled)
-	assert.True(t, rt.hr.enabled)
-
-	rt.MakePrimary()
-	assert.True(t, rt.hw.isOpen)
-	assert.False(t, rt.hr.isOpen)
-	assert.True(t, rt.isPrimary)
-
-	lag, err := rt.Status()
-	assert.NoError(t, err)
-	assert.Equal(t, time.Duration(0), lag)
-
-	rt.MakeNonPrimary()
-	assert.False(t, rt.hw.isOpen)
-	assert.True(t, rt.hr.isOpen)
-	assert.False(t, rt.isPrimary)
-
-	rt.hr.lastKnownLag = 1 * time.Second
-	lag, err = rt.Status()
-	assert.NoError(t, err)
-	assert.Equal(t, 1*time.Second, lag)
-
-	rt.Close()
-	assert.False(t, rt.hw.isOpen)
-	assert.False(t, rt.hr.isOpen)
-
-	cfg.ReplicationTracker.Mode = tabletenv.Polling
-	rt = NewReplTracker(env, alias)
-	rt.InitDBConfig(target, mysqld)
-	assert.Equal(t, tabletenv.Polling, rt.mode)
-	assert.Equal(t, mysqld, rt.poller.mysqld)
-	assert.False(t, rt.hw.enabled)
-	assert.False(t, rt.hr.enabled)
-
-	rt.MakeNonPrimary()
-	assert.False(t, rt.hw.isOpen)
-	assert.False(t, rt.hr.isOpen)
-	assert.False(t, rt.isPrimary)
-
-	mysqld.ReplicationStatusError = errors.New("err")
-	_, err = rt.Status()
-	assert.Equal(t, "err", err.Error())
+	t.Run("always-on heartbeat", func(t *testing.T) {
+		rt := NewReplTracker(env, alias)
+		rt.InitDBConfig(target, mysqld)
+		assert.Equal(t, tabletenv.Heartbeat, rt.mode)
+		assert.Equal(t, HeartbeatConfigTypeAlways, rt.hw.configType)
+		assert.Zero(t, rt.hw.onDemandDuration)
+		assert.Zero(t, rt.hw.onDemandDuration)
+		assert.True(t, rt.hr.enabled)
+
+		rt.MakePrimary()
+		assert.True(t, rt.hw.isOpen)
+		assert.False(t, rt.hr.isOpen)
+		assert.True(t, rt.isPrimary)
+
+		lag, err := rt.Status()
+		assert.NoError(t, err)
+		assert.Equal(t, time.Duration(0), lag)
+
+		rt.MakeNonPrimary()
+		assert.False(t, rt.hw.isOpen)
+		assert.True(t, rt.hr.isOpen)
+		assert.False(t, rt.isPrimary)
+
+		rt.hr.lastKnownLag = 1 * time.Second
+		lag, err = rt.Status()
+		assert.NoError(t, err)
+		assert.Equal(t, 1*time.Second, lag)
+
+		rt.Close()
+		assert.False(t, rt.hw.isOpen)
+		assert.False(t, rt.hr.isOpen)
+	})
+	t.Run("disabled heartbeat", func(t *testing.T) {
+		cfg.ReplicationTracker.Mode = tabletenv.Polling
+		rt := NewReplTracker(env, alias)
+		rt.InitDBConfig(target, mysqld)
+		assert.Equal(t, tabletenv.Polling, rt.mode)
+		assert.Equal(t, mysqld, rt.poller.mysqld)
+		assert.Equal(t, HeartbeatConfigTypeNone, rt.hw.configType)
+		assert.Equal(t, defaultOnDemandDuration, rt.hw.onDemandDuration)
+		assert.NotZero(t, rt.hw.onDemandDuration)
+		assert.False(t, rt.hr.enabled)
+
+		rt.MakeNonPrimary()
+		assert.False(t, rt.hw.isOpen)
+		assert.False(t, rt.hr.isOpen)
+		assert.False(t, rt.isPrimary)
+
+		mysqld.ReplicationStatusError = errors.New("err")
+		_, err := rt.Status()
+		assert.Equal(t, "err", err.Error())
+	})
+	t.Run("on-demand heartbeat", func(t *testing.T) {
+		cfg.ReplicationTracker.Mode = tabletenv.Heartbeat
+		cfg.ReplicationTracker.HeartbeatOnDemand = time.Second
+
+		rt := NewReplTracker(env, alias)
+		rt.InitDBConfig(target, mysqld)
+		assert.Equal(t, tabletenv.Heartbeat, rt.mode)
+		assert.Equal(t, HeartbeatConfigTypeOnDemand, rt.hw.configType)
+		assert.Equal(t, time.Second, rt.hw.onDemandDuration)
+		assert.NotZero(t, rt.hw.onDemandDuration)
+		assert.True(t, rt.hr.enabled)
+
+		rt.MakePrimary()
+		assert.True(t, rt.hw.isOpen)
+		assert.False(t, rt.hr.isOpen)
+		assert.True(t, rt.isPrimary)
+
+		lag, err := rt.Status()
+		assert.NoError(t, err)
+		assert.Equal(t, time.Duration(0), lag)
+
+		rt.MakeNonPrimary()
+		assert.False(t, rt.hw.isOpen)
+		assert.True(t, rt.hr.isOpen)
+		assert.False(t, rt.isPrimary)
+
+		rt.hr.lastKnownLag = 1 * time.Second
+		lag, err = rt.Status()
+		assert.NoError(t, err)
+		assert.Equal(t, 1*time.Second, lag)
+
+		rt.Close()
+		assert.False(t, rt.hw.isOpen)
+		assert.False(t, rt.hr.isOpen)
+	})
 }