Refactor collection_jitter and flush_jitter

use a common function between collection_jitter and flush_jitter. which
creates the same behavior between the two options.

going forward, both jitters will be random sleeps that get re-evaluated
at runtime for every interval (previously only collection_jitter did
this)

also fixes behavior so that both jitters will exit in the event of a
process exit.

closes #1296

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ### Release Notes
 
+- `flush_jitter` behavior has been changed. The random jitter will now be
+evaluated at every flush interval, rather than once at startup. This makes it
+consistent with the behavior of `collection_jitter`.
+
 - All AWS plugins now utilize a standard mechanism for evaluating credentials.
 This allows all AWS plugins to support environment variables, shared credential
 files & profiles, and role assumptions. See the specific plugin README for
@@ -31,6 +35,7 @@ time before a new metric is included by the plugin.
 - [#1278](https://github.com/influxdata/telegraf/pull/1278): RabbitMQ input: made url parameter optional by using DefaultURL (http://localhost:15672) if not specified
 - [#1197](https://github.com/influxdata/telegraf/pull/1197): Limit AWS GetMetricStatistics requests to 10 per second.
 - [#1278](https://github.com/influxdata/telegraf/pull/1278) & [#1288](https://github.com/influxdata/telegraf/pull/1288) & [#1295](https://github.com/influxdata/telegraf/pull/1295): RabbitMQ/Apache/InfluxDB inputs: made url(s) parameter optional by using reasonable input defaults if not specified
+- [#1296](https://github.com/influxdata/telegraf/issues/1296): Refactor of flush_jitter argument.
 
 ### Bugfixes
 

agent/agent.go

@@ -1,17 +1,15 @@
 package agent
 
 import (
-	cryptorand "crypto/rand"
 	"fmt"
 	"log"
-	"math/big"
-	"math/rand"
 	"os"
 	"runtime"
 	"sync"
 	"time"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/internal/config"
 	"github.com/influxdata/telegraf/internal/models"
 )
@@ -115,27 +113,16 @@ func (a *Agent) gatherer(
 	ticker := time.NewTicker(interval)
 	defer ticker.Stop()
 
-	jitter := a.Config.Agent.CollectionJitter.Duration.Nanoseconds()
-
 	for {
 		var outerr error
-		start := time.Now()
 
 		acc := NewAccumulator(input.Config, metricC)
 		acc.SetDebug(a.Config.Agent.Debug)
 		acc.setDefaultTags(a.Config.Tags)
 
-		if jitter != 0 {
-			nanoSleep := rand.Int63n(jitter)
-			d, err := time.ParseDuration(fmt.Sprintf("%dns", nanoSleep))
-			if err != nil {
-				log.Printf("Jittering collection interval failed for plugin %s",
-					input.Name)
-			} else {
-				time.Sleep(d)
-			}
-		}
+		internal.RandomSleep(a.Config.Agent.CollectionJitter.Duration, shutdown)
 
+		start := time.Now()
 		gatherWithTimeout(shutdown, input, acc, interval)
 		elapsed := time.Since(start)
 
@@ -274,6 +261,7 @@ func (a *Agent) flusher(shutdown chan struct{}, metricC chan telegraf.Metric) er
 			a.flush()
 			return nil
 		case <-ticker.C:
+			internal.RandomSleep(a.Config.Agent.FlushJitter.Duration, shutdown)
 			a.flush()
 		case m := <-metricC:
 			for _, o := range a.Config.Outputs {
@@ -283,35 +271,10 @@ func (a *Agent) flusher(shutdown chan struct{}, metricC chan telegraf.Metric) er
 	}
 }
 
-// jitterInterval applies the the interval jitter to the flush interval using
-// crypto/rand number generator
-func jitterInterval(ininterval, injitter time.Duration) time.Duration {
-	var jitter int64
-	outinterval := ininterval
-	if injitter.Nanoseconds() != 0 {
-		maxjitter := big.NewInt(injitter.Nanoseconds())
-		if j, err := cryptorand.Int(cryptorand.Reader, maxjitter); err == nil {
-			jitter = j.Int64()
-		}
-		outinterval = time.Duration(jitter + ininterval.Nanoseconds())
-	}
-
-	if outinterval.Nanoseconds() < time.Duration(500*time.Millisecond).Nanoseconds() {
-		log.Printf("Flush interval %s too low, setting to 500ms\n", outinterval)
-		outinterval = time.Duration(500 * time.Millisecond)
-	}
-
-	return outinterval
-}
-
 // Run runs the agent daemon, gathering every Interval
 func (a *Agent) Run(shutdown chan struct{}) error {
 	var wg sync.WaitGroup
 
-	a.Config.Agent.FlushInterval.Duration = jitterInterval(
-		a.Config.Agent.FlushInterval.Duration,
-		a.Config.Agent.FlushJitter.Duration)
-
 	log.Printf("Agent Config: Interval:%s, Debug:%#v, Quiet:%#v, Hostname:%#v, "+
 		"Flush Interval:%s \n",
 		a.Config.Agent.Interval.Duration, a.Config.Agent.Debug, a.Config.Agent.Quiet,

agent/agent_test.go

@@ -2,7 +2,6 @@ package agent
 
 import (
 	"testing"
-	"time"
 
 	"github.com/influxdata/telegraf/internal/config"
 
@@ -110,75 +109,3 @@ func TestAgent_LoadOutput(t *testing.T) {
 	a, _ = NewAgent(c)
 	assert.Equal(t, 3, len(a.Config.Outputs))
 }
-
-func TestAgent_ZeroJitter(t *testing.T) {
-	flushinterval := jitterInterval(time.Duration(10*time.Second),
-		time.Duration(0*time.Second))
-
-	actual := flushinterval.Nanoseconds()
-	exp := time.Duration(10 * time.Second).Nanoseconds()
-
-	if actual != exp {
-		t.Errorf("Actual %v, expected %v", actual, exp)
-	}
-}
-
-func TestAgent_ZeroInterval(t *testing.T) {
-	min := time.Duration(500 * time.Millisecond).Nanoseconds()
-	max := time.Duration(5 * time.Second).Nanoseconds()
-
-	for i := 0; i < 1000; i++ {
-		flushinterval := jitterInterval(time.Duration(0*time.Second),
-			time.Duration(5*time.Second))
-		actual := flushinterval.Nanoseconds()
-
-		if actual > max {
-			t.Errorf("Didn't expect interval %d to be > %d", actual, max)
-			break
-		}
-		if actual < min {
-			t.Errorf("Didn't expect interval %d to be < %d", actual, min)
-			break
-		}
-	}
-}
-
-func TestAgent_ZeroBoth(t *testing.T) {
-	flushinterval := jitterInterval(time.Duration(0*time.Second),
-		time.Duration(0*time.Second))
-
-	actual := flushinterval
-	exp := time.Duration(500 * time.Millisecond)
-
-	if actual != exp {
-		t.Errorf("Actual %v, expected %v", actual, exp)
-	}
-}
-
-func TestAgent_JitterMax(t *testing.T) {
-	max := time.Duration(32 * time.Second).Nanoseconds()
-
-	for i := 0; i < 1000; i++ {
-		flushinterval := jitterInterval(time.Duration(30*time.Second),
-			time.Duration(2*time.Second))
-		actual := flushinterval.Nanoseconds()
-		if actual > max {
-			t.Errorf("Didn't expect interval %d to be > %d", actual, max)
-			break
-		}
-	}
-}
-
-func TestAgent_JitterMin(t *testing.T) {
-	min := time.Duration(30 * time.Second).Nanoseconds()
-
-	for i := 0; i < 1000; i++ {
-		flushinterval := jitterInterval(time.Duration(30*time.Second),
-			time.Duration(2*time.Second))
-		actual := flushinterval.Nanoseconds()
-		if actual < min {
-			t.Errorf("Didn't expect interval %d to be < %d", actual, min)
-			break
-		}
-	}
-}

internal/config/config.go

@@ -58,7 +58,6 @@ func NewConfig() *Config {
 			Interval:      internal.Duration{Duration: 10 * time.Second},
 			RoundInterval: true,
 			FlushInterval: internal.Duration{Duration: 10 * time.Second},
-			FlushJitter:   internal.Duration{Duration: 5 * time.Second},
 		},
 
 		Tags:          make(map[string]string),

internal/internal.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"math/big"
 	"os"
 	"os/exec"
 	"strconv"
@@ -228,3 +229,27 @@ func CompileFilter(filters []string) (glob.Glob, error) {
 	}
 	return out, err
 }
+
+// RandomSleep will sleep for a random amount of time up to max.
+// If the shutdown channel is closed, it will return before it has finished
+// sleeping.
+func RandomSleep(max time.Duration, shutdown chan struct{}) {
+	if max == 0 {
+		return
+	}
+	maxSleep := big.NewInt(max.Nanoseconds())
+
+	var sleepns int64
+	if j, err := rand.Int(rand.Reader, maxSleep); err == nil {
+		sleepns = j.Int64()
+	}
+
+	t := time.NewTimer(time.Nanosecond * time.Duration(sleepns))
+	select {
+	case <-t.C:
+		return
+	case <-shutdown:
+		t.Stop()
+		return
+	}
+}

internal/internal_test.go

@@ -137,3 +137,28 @@ func TestCompileFilter(t *testing.T) {
 	assert.True(t, f.Match("mem"))
 	assert.True(t, f.Match("network"))
 }
+
+func TestRandomSleep(t *testing.T) {
+	// test that zero max returns immediately
+	s := time.Now()
+	RandomSleep(time.Duration(0), make(chan struct{}))
+	elapsed := time.Since(s)
+	assert.True(t, elapsed < time.Millisecond)
+
+	// test that max sleep is respected
+	s = time.Now()
+	RandomSleep(time.Millisecond*50, make(chan struct{}))
+	elapsed = time.Since(s)
+	assert.True(t, elapsed < time.Millisecond*50)
+
+	// test that shutdown is respected
+	s = time.Now()
+	shutdown := make(chan struct{})
+	go func() {
+		time.Sleep(time.Millisecond * 100)
+		close(shutdown)
+	}()
+	RandomSleep(time.Second, shutdown)
+	elapsed = time.Since(s)
+	assert.True(t, elapsed < time.Millisecond*150)
+}