Scales coordinate sends to hit a fixed aggregate rate across the cluster.

command/agent/agent.go

@@ -566,7 +566,9 @@ func (a *Agent) ResumeSync() {
 // to the server. Closing the agent's shutdownChannel will cause this to exit.
 func (a *Agent) sendCoordinate() {
 	for {
-		intv := aeScale(a.config.SyncCoordinateInterval, len(a.LANMembers()))
+		rate := a.config.SyncCoordinateRateTarget
+		min := a.config.SyncCoordinateIntervalMin
+		intv := rateScaledInterval(rate, min, len(a.LANMembers()))
 		intv = intv + randomStagger(intv)
 
 		select {

command/agent/config.go

@@ -375,12 +375,17 @@ type Config struct {
 	// DisableCoordinates controls features related to network coordinates.
 	DisableCoordinates bool `mapstructure:"disable_coordinates" json:"-"`
 
-	// SyncCoordinateInterval controls the interval for sending network
-	// coordinates to the server. Defaults to every 20s, but scales up as
-	// the number of nodes increases in the network, to prevent servers from
-	// being overwhelmed. If you update this, you may need to adjust the
-	// tuning of CoordinateUpdatePeriod and CoordinateUpdateMaxBatchSize.
-	SyncCoordinateInterval time.Duration `mapstructure:"-" json:"-"`
+	// SyncCoordinateRateTarget controls the rate for sending network
+	// coordinates to the server, in updates per second. This is the max rate
+	// that the server supports, so we scale our interval based on the size
+	// of the cluster to try to achieve this in aggregate at the server.
+	SyncCoordinateRateTarget float64 `mapstructure:"-" json:"-"`
+
+	// SyncCoordinateIntervalMin sets the minimum interval that coordinates
+	// will be sent to the server. We scale the interval based on the cluster
+	// size, but below a certain interval it doesn't make sense send them any
+	// faster.
+	SyncCoordinateIntervalMin time.Duration `mapstructure:"-" json:"-"`
 
 	// Checks holds the provided check definitions
 	Checks []*CheckDefinition `mapstructure:"-" json:"-"`
@@ -477,7 +482,14 @@ func DefaultConfig() *Config {
 		CheckUpdateInterval:       5 * time.Minute,
 		AEInterval:                time.Minute,
 		DisableCoordinates:        false,
-		SyncCoordinateInterval: 20 * time.Second,
+
+		// SyncCoordinateRateTarget is set based on the rate that we want
+		// the server to handle as an aggregate across the entire cluster.
+		// If you update this, you'll need to adjust CoordinateUpdate* in
+		// the server-side config accordingly.
+		SyncCoordinateRateTarget:  100.0, // updates / second
+		SyncCoordinateIntervalMin: 5 * time.Second,
+
 		ACLTTL:                    30 * time.Second,
 		ACLDownPolicy:             "extend-cache",
 		ACLDefaultPolicy:          "allow",

command/agent/local_test.go

@@ -806,9 +806,10 @@ func TestAgent_nestedPauseResume(t *testing.T) {
 
 func TestAgent_sendCoordinate(t *testing.T) {
 	conf := nextConfig()
-	conf.SyncCoordinateInterval = 10 * time.Millisecond
+	conf.SyncCoordinateRateTarget = 10.0 // updates/sec
+	conf.SyncCoordinateIntervalMin = 1 * time.Millisecond
 	conf.ConsulConfig.CoordinateUpdatePeriod = 100 * time.Millisecond
-	conf.ConsulConfig.CoordinateUpdateBatchSize = 15
+	conf.ConsulConfig.CoordinateUpdateBatchSize = 10
 	conf.ConsulConfig.CoordinateUpdateMaxBatches = 1
 	dir, agent := makeAgent(t, conf)
 	defer os.RemoveAll(dir)

command/agent/util.go

@@ -39,6 +39,17 @@ func aeScale(interval time.Duration, n int) time.Duration {
 	return time.Duration(multiplier) * interval
 }
 
+// rateScaledInterval is used to choose an interval to perform an action in order
+// to target an aggregate number of actions per second across the whole cluster.
+func rateScaledInterval(rate float64, min time.Duration, n int) time.Duration {
+	interval := time.Duration(float64(time.Second) * float64(n) / rate)
+	if interval < min {
+		return min
+	}
+
+	return interval
+}
+
 // Returns a random stagger interval between 0 and the duration
 func randomStagger(intv time.Duration) time.Duration {
 	return time.Duration(uint64(rand.Int63()) % uint64(intv))

command/agent/util_test.go

@@ -24,6 +24,29 @@ func TestAEScale(t *testing.T) {
 	}
 }
 
+func TestRateScaledInterval(t *testing.T) {
+	min := 1*time.Second
+	rate := 200.0
+	if v := rateScaledInterval(rate, min, 0); v != min {
+		t.Fatalf("Bad: %v", v)
+	}
+	if v := rateScaledInterval(rate, min, 100); v != min {
+		t.Fatalf("Bad: %v", v)
+	}
+	if v := rateScaledInterval(rate, min, 200); v != 1*time.Second {
+		t.Fatalf("Bad: %v", v)
+	}
+	if v := rateScaledInterval(rate, min, 1000); v != 5*time.Second {
+		t.Fatalf("Bad: %v", v)
+	}
+	if v := rateScaledInterval(rate, min, 5000); v != 25*time.Second {
+		t.Fatalf("Bad: %v", v)
+	}
+	if v := rateScaledInterval(rate, min, 10000); v != 50*time.Second {
+		t.Fatalf("Bad: %v", v)
+	}
+}
+
 func TestRandomStagger(t *testing.T) {
 	intv := time.Minute
 	for i := 0; i < 10; i++ {

consul/config.go

@@ -276,13 +276,11 @@ func DefaultConfig() *Config {
 		SessionTTLMin:           10 * time.Second,
 		DisableCoordinates:      false,
 
-		// SyncCoordinateInterval defaults to 20 seconds, and scales up
-		// as the number of nodes in the cluster goes up. For 100k nodes,
-		// it will move up to 201 seconds, which gives an update rate of
-		// just under 500 per second coming in from the clients. With this
-		// tuning we will be doing 1 transaction per second at this load.
+		// These are tuned to provide a total throughput of 128 updates
+		// per second. If you update these, you should update the client-
+		// side SyncCoordinateRateTarget parameter accordingly.
 		CoordinateUpdatePeriod:       5 * time.Second,
-		CoordinateUpdateBatchSize:    512,
+		CoordinateUpdateBatchSize:    128,
 		CoordinateUpdateMaxBatches:   5,
 	}
 

consul/coordinate_endpoint.go

@@ -60,7 +60,7 @@ func (c *Coordinate) batchApplyUpdates() error {
 	limit := c.srv.config.CoordinateUpdateBatchSize * c.srv.config.CoordinateUpdateMaxBatches
 	size := len(pending)
 	if size > limit {
-		c.srv.logger.Printf("[ERR] consul.coordinate: Discarded %d coordinate updates; increase SyncCoordinateInterval", size - limit)
+		c.srv.logger.Printf("[WARN] consul.coordinate: Discarded %d coordinate updates", size - limit)
 		size = limit
 	}