Allow tuning of heartbeat ttls

command/agent/agent.go

@@ -192,12 +192,14 @@ func convertServerConfig(agentConfig *Config, logOutput io.Writer) (*nomad.Confi
 		conf.DeploymentGCThreshold = dur
 	}
 
-	if heartbeatGrace := agentConfig.Server.HeartbeatGrace; heartbeatGrace != "" {
-		dur, err := time.ParseDuration(heartbeatGrace)
-		if err != nil {
-			return nil, err
-		}
-		conf.HeartbeatGrace = dur
+	if heartbeatGrace := agentConfig.Server.HeartbeatGrace; heartbeatGrace != 0 {
+		conf.HeartbeatGrace = heartbeatGrace
+	}
+	if min := agentConfig.Server.MinHeartbeatTTL; min != 0 {
+		conf.MinHeartbeatTTL = min
+	}
+	if maxHPS := agentConfig.Server.MaxHeartbeatsPerSecond; maxHPS != 0 {
+		conf.MaxHeartbeatsPerSecond = maxHPS
 	}
 
 	if *agentConfig.Consul.AutoAdvertise && agentConfig.Consul.ServerServiceName == "" {

command/agent/agent_test.go

@@ -233,22 +233,22 @@ func TestAgent_ServerConfig(t *testing.T) {
 		t.Fatalf("expect 10s, got: %s", threshold)
 	}
 
-	conf.Server.HeartbeatGrace = "42g"
-	if err := conf.normalizeAddrs(); err != nil {
-		t.Fatalf("error normalizing config: %v", err)
-	}
+	conf.Server.HeartbeatGrace = 37 * time.Second
 	out, err = a.serverConfig()
-	if err == nil || !strings.Contains(err.Error(), "unknown unit") {
-		t.Fatalf("expected unknown unit error, got: %#v", err)
+	if threshold := out.HeartbeatGrace; threshold != time.Second*37 {
+		t.Fatalf("expect 37s, got: %s", threshold)
 	}
 
-	conf.Server.HeartbeatGrace = "37s"
-	if err := conf.normalizeAddrs(); err != nil {
-		t.Fatalf("error normalizing config: %v", err)
+	conf.Server.MinHeartbeatTTL = 37 * time.Second
+	out, err = a.serverConfig()
+	if min := out.MinHeartbeatTTL; min != time.Second*37 {
+		t.Fatalf("expect 37s, got: %s", min)
 	}
+
+	conf.Server.MaxHeartbeatsPerSecond = 11.0
 	out, err = a.serverConfig()
-	if threshold := out.HeartbeatGrace; threshold != time.Second*37 {
-		t.Fatalf("expect 37s, got: %s", threshold)
+	if max := out.MaxHeartbeatsPerSecond; max != 11.0 {
+		t.Fatalf("expect 11, got: %s", max)
 	}
 
 	// Defaults to the global bind addr

command/agent/config-test-fixtures/basic.hcl

@@ -73,6 +73,8 @@ server {
 	eval_gc_threshold = "12h"
 	deployment_gc_threshold = "12h"
 	heartbeat_grace   = "30s"
+	min_heartbeat_ttl = "33s"
+	max_heartbeats_per_second = 11.0
 	retry_join = [ "1.1.1.1", "2.2.2.2" ]
 	start_join = [ "1.1.1.1", "2.2.2.2" ]
 	retry_max = 3

command/agent/config.go

@@ -277,7 +277,16 @@ type ServerConfig struct {
 
 	// HeartbeatGrace is the grace period beyond the TTL to account for network,
 	// processing delays and clock skew before marking a node as "down".
-	HeartbeatGrace string `mapstructure:"heartbeat_grace"`
+	HeartbeatGrace time.Duration `mapstructure:"heartbeat_grace"`
+
+	// MinHeartbeatTTL is the minimum time between heartbeats. This is used as
+	// a floor to prevent excessive updates.
+	MinHeartbeatTTL time.Duration `mapstructure:"min_heartbeat_ttl"`
+
+	// MaxHeartbeatsPerSecond is the maximum target rate of heartbeats
+	// being processed per second. This allows the TTL to be increased
+	// to meet the target rate.
+	MaxHeartbeatsPerSecond float64 `mapstructure:"max_heartbeats_per_second"`
 
 	// StartJoin is a list of addresses to attempt to join when the
 	// agent starts. If Serf is unable to communicate with any of these
@@ -924,9 +933,15 @@ func (a *ServerConfig) Merge(b *ServerConfig) *ServerConfig {
 	if b.DeploymentGCThreshold != "" {
 		result.DeploymentGCThreshold = b.DeploymentGCThreshold
 	}
-	if b.HeartbeatGrace != "" {
+	if b.HeartbeatGrace != 0 {
 		result.HeartbeatGrace = b.HeartbeatGrace
 	}
+	if b.MinHeartbeatTTL != 0 {
+		result.MinHeartbeatTTL = b.MinHeartbeatTTL
+	}
+	if b.MaxHeartbeatsPerSecond != 0.0 {
+		result.MaxHeartbeatsPerSecond = b.MaxHeartbeatsPerSecond
+	}
 	if b.RetryMaxAttempts != 0 {
 		result.RetryMaxAttempts = b.RetryMaxAttempts
 	}

command/agent/config_parse.go

@@ -506,6 +506,8 @@ func parseServer(result **ServerConfig, list *ast.ObjectList) error {
 		"job_gc_threshold",
 		"deployment_gc_threshold",
 		"heartbeat_grace",
+		"min_heartbeat_ttl",
+		"max_heartbeats_per_second",
 		"start_join",
 		"retry_join",
 		"retry_max",
@@ -523,7 +525,15 @@ func parseServer(result **ServerConfig, list *ast.ObjectList) error {
 	}
 
 	var config ServerConfig
-	if err := mapstructure.WeakDecode(m, &config); err != nil {
+	dec, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
+		WeaklyTypedInput: true,
+		Result:           &config,
+	})
+	if err != nil {
+		return err
+	}
+	if err := dec.Decode(m); err != nil {
 		return err
 	}
 

command/agent/config_parse_test.go

@@ -82,23 +82,25 @@ func TestConfig_Parse(t *testing.T) {
 					NoHostUUID:            helper.BoolToPtr(false),
 				},
 				Server: &ServerConfig{
-					Enabled:               true,
-					BootstrapExpect:       5,
-					DataDir:               "/tmp/data",
-					ProtocolVersion:       3,
-					NumSchedulers:         2,
-					EnabledSchedulers:     []string{"test"},
-					NodeGCThreshold:       "12h",
-					EvalGCThreshold:       "12h",
-					JobGCThreshold:        "12h",
-					DeploymentGCThreshold: "12h",
-					HeartbeatGrace:        "30s",
-					RetryJoin:             []string{"1.1.1.1", "2.2.2.2"},
-					StartJoin:             []string{"1.1.1.1", "2.2.2.2"},
-					RetryInterval:         "15s",
-					RejoinAfterLeave:      true,
-					RetryMaxAttempts:      3,
-					EncryptKey:            "abc",
+					Enabled:                true,
+					BootstrapExpect:        5,
+					DataDir:                "/tmp/data",
+					ProtocolVersion:        3,
+					NumSchedulers:          2,
+					EnabledSchedulers:      []string{"test"},
+					NodeGCThreshold:        "12h",
+					EvalGCThreshold:        "12h",
+					JobGCThreshold:         "12h",
+					DeploymentGCThreshold:  "12h",
+					HeartbeatGrace:         30 * time.Second,
+					MinHeartbeatTTL:        33 * time.Second,
+					MaxHeartbeatsPerSecond: 11.0,
+					RetryJoin:              []string{"1.1.1.1", "2.2.2.2"},
+					StartJoin:              []string{"1.1.1.1", "2.2.2.2"},
+					RetryInterval:          "15s",
+					RejoinAfterLeave:       true,
+					RetryMaxAttempts:       3,
+					EncryptKey:             "abc",
 				},
 				Telemetry: &Telemetry{
 					StatsiteAddr:             "127.0.0.1:1234",

command/agent/config_test.go

@@ -90,13 +90,15 @@ func TestConfig_Merge(t *testing.T) {
 			},
 		},
 		Server: &ServerConfig{
-			Enabled:         false,
-			BootstrapExpect: 1,
-			DataDir:         "/tmp/data1",
-			ProtocolVersion: 1,
-			NumSchedulers:   1,
-			NodeGCThreshold: "1h",
-			HeartbeatGrace:  "30s",
+			Enabled:                false,
+			BootstrapExpect:        1,
+			DataDir:                "/tmp/data1",
+			ProtocolVersion:        1,
+			NumSchedulers:          1,
+			NodeGCThreshold:        "1h",
+			HeartbeatGrace:         30 * time.Second,
+			MinHeartbeatTTL:        30 * time.Second,
+			MaxHeartbeatsPerSecond: 30.0,
 		},
 		Ports: &Ports{
 			HTTP: 4646,
@@ -220,19 +222,21 @@ func TestConfig_Merge(t *testing.T) {
 			GCInodeUsageThreshold: 86,
 		},
 		Server: &ServerConfig{
-			Enabled:           true,
-			BootstrapExpect:   2,
-			DataDir:           "/tmp/data2",
-			ProtocolVersion:   2,
-			NumSchedulers:     2,
-			EnabledSchedulers: []string{structs.JobTypeBatch},
-			NodeGCThreshold:   "12h",
-			HeartbeatGrace:    "2m",
-			RejoinAfterLeave:  true,
-			StartJoin:         []string{"1.1.1.1"},
-			RetryJoin:         []string{"1.1.1.1"},
-			RetryInterval:     "10s",
-			retryInterval:     time.Second * 10,
+			Enabled:                true,
+			BootstrapExpect:        2,
+			DataDir:                "/tmp/data2",
+			ProtocolVersion:        2,
+			NumSchedulers:          2,
+			EnabledSchedulers:      []string{structs.JobTypeBatch},
+			NodeGCThreshold:        "12h",
+			HeartbeatGrace:         2 * time.Minute,
+			MinHeartbeatTTL:        2 * time.Minute,
+			MaxHeartbeatsPerSecond: 200.0,
+			RejoinAfterLeave:       true,
+			StartJoin:              []string{"1.1.1.1"},
+			RetryJoin:              []string{"1.1.1.1"},
+			RetryInterval:          "10s",
+			retryInterval:          time.Second * 10,
 		},
 		Ports: &Ports{
 			HTTP: 20000,

website/source/docs/agent/configuration/server.html.md

@@ -80,6 +80,23 @@ server {
   deployment must be in the terminal state before it is eligible for garbage
   collection. This is specified using a label suffix like "30s" or "1h".
 
+- `heartbeat_grace` `(string: "10s")` - Specifies the additional time given as a
+  grace period beyond the heartbeat TTL of nodes to account for network and
+  processing delays as well as clock skew. This is specified using a label
+  suffix like "30s" or "1h".
+
+- `min_heartbeat_ttl` `(string: "10s")` - Specifies the minimum time between
+  node heartbeats. This is used as a floor to prevent excessive updates. This is
+  specified using a label suffix like "30s" or "1h". Lowering the minimum TTL is
+  a tradeoff as it lowers failure detection time of nodes at the tradeoff of
+  false positives and increased load on the leader.
+
+- `max_heartbeats_per_second` `(float: 50.0)` - Specifies the maximum target
+  rate of heartbeats being processed per second. This allows the TTL to be
+  increased to meet the target rate. Increasing the maximum heartbeats per
+  second is a tradeoff as it lowers failure detection time of nodes at the
+  tradeoff of false positives and increased load on the leader.
+
 - `num_schedulers` `(int: [num-cores])` - Specifies the number of parallel
   scheduler threads to run. This can be as many as one per core, or `0` to
   disallow this server from making any scheduling decisions. This defaults to