Use consul/lib's RateScaledInterval

nomad/heartbeat.go

@@ -4,6 +4,7 @@ import (
 	"time"
 
 	"github.com/armon/go-metrics"
+	"github.com/hashicorp/consul/lib"
 	"github.com/hashicorp/nomad/nomad/structs"
 )
 
@@ -49,8 +50,7 @@ func (s *Server) resetHeartbeatTimer(id string) (time.Duration, error) {
 
 	// Compute the target TTL value
 	n := len(s.heartbeatTimers)
-	ttl := rateScaledInterval(s.config.MaxHeartbeatsPerSecond,
-		s.config.MinHeartbeatTTL, n)
+	ttl := lib.RateScaledInterval(s.config.MaxHeartbeatsPerSecond, s.config.MinHeartbeatTTL, n)
 	ttl += randomStagger(ttl)
 
 	// Reset the TTL

nomad/util.go

@@ -122,16 +122,6 @@ func maxUint64(a, b uint64) uint64 {
 	return b
 }
 
-// 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
-}
-
 // seedRandom seeds the global random variable using a cryptographically random
 // seed. It returns an error if determing the random seed fails.
 func seedRandom() error {

nomad/util_test.go

@@ -98,26 +98,3 @@ func TestMaxUint64(t *testing.T) {
 		t.Fatalf("bad")
 	}
 }
-
-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)
-	}
-}

vendor/github.com/hashicorp/consul/lib/cluster.go

@@ -0,0 +1,56 @@
+package lib
+
+import (
+	"math/rand"
+	"time"
+)
+
+// DurationMinusBuffer returns a duration, minus a buffer and jitter
+// subtracted from the duration.  This function is used primarily for
+// servicing Consul TTL Checks in advance of the TTL.
+func DurationMinusBuffer(intv time.Duration, buffer time.Duration, jitter int64) time.Duration {
+	d := intv - buffer
+	if jitter == 0 {
+		d -= RandomStagger(d)
+	} else {
+		d -= RandomStagger(time.Duration(int64(d) / jitter))
+	}
+	return d
+}
+
+// DurationMinusBufferDomain returns the domain of valid durations from a
+// call to DurationMinusBuffer.  This function is used to check user
+// specified input values to DurationMinusBuffer.
+func DurationMinusBufferDomain(intv time.Duration, buffer time.Duration, jitter int64) (min time.Duration, max time.Duration) {
+	max = intv - buffer
+	if jitter == 0 {
+		min = max
+	} else {
+		min = max - time.Duration(int64(max)/jitter)
+	}
+	return min, max
+}
+
+// Returns a random stagger interval between 0 and the duration
+func RandomStagger(intv time.Duration) time.Duration {
+	if intv == 0 {
+		return 0
+	}
+	return time.Duration(uint64(rand.Int63()) % uint64(intv))
+}
+
+// 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 {
+	const minRate = 1 / 86400 // 1/(1 * time.Day)
+	if rate <= minRate {
+		return min
+	}
+	interval := time.Duration(float64(time.Second) * float64(n) / rate)
+	if interval < min {
+		return min
+	}
+
+	return interval
+}

vendor/github.com/hashicorp/consul/lib/math.go

@@ -0,0 +1,22 @@
+package lib
+
+func AbsInt(a int) int {
+	if a > 0 {
+		return a
+	}
+	return a * -1
+}
+
+func MaxInt(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func MinInt(a, b int) int {
+	if a > b {
+		return b
+	}
+	return a
+}

vendor/github.com/hashicorp/consul/lib/rand.go

@@ -0,0 +1,34 @@
+package lib
+
+import (
+	crand "crypto/rand"
+	"math"
+	"math/big"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+var (
+	once sync.Once
+
+	// SeededSecurely is set to true if a cryptographically secure seed
+	// was used to initialize rand.  When false, the start time is used
+	// as a seed.
+	SeededSecurely bool
+)
+
+// SeedMathRand provides weak, but guaranteed seeding, which is better than
+// running with Go's default seed of 1.  A call to SeedMathRand() is expected
+// to be called via init(), but never a second time.
+func SeedMathRand() {
+	once.Do(func() {
+		n, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
+		if err != nil {
+			rand.Seed(time.Now().UTC().UnixNano())
+			return
+		}
+		rand.Seed(n.Int64())
+		SeededSecurely = true
+	})
+}

vendor/github.com/hashicorp/consul/lib/string.go

@@ -0,0 +1,11 @@
+package lib
+
+// StrContains checks if a list contains a string
+func StrContains(l []string, s string) bool {
+	for _, v := range l {
+		if v == s {
+			return true
+		}
+	}
+	return false
+}