Revert "Refactor throttle timer"

common/repeat_timer_test.go

@@ -43,7 +43,7 @@ func TestRepeat(test *testing.T) {
 	short := time.Duration(20) * time.Millisecond
 	// delay waits for cnt durations, an a little extra
 	delay := func(cnt int) time.Duration {
-		return time.Duration(cnt)*dur + time.Duration(5)*time.Millisecond
+		return time.Duration(cnt)*dur + time.Millisecond
 	}
 	t := NewRepeatTimer("bar", dur)
 

common/throttle_timer.go

@@ -1,6 +1,7 @@
 package common
 
 import (
+	"sync"
 	"time"
 )
 
@@ -11,117 +12,64 @@ If a long continuous burst of .Set() calls happens, ThrottleTimer fires
 at most once every "dur".
 */
 type ThrottleTimer struct {
-	Name   string
-	Ch     <-chan struct{}
-	input  chan command
-	output chan<- struct{}
-	dur    time.Duration
+	Name string
+	Ch   chan struct{}
+	quit chan struct{}
+	dur  time.Duration
 
+	mtx   sync.Mutex
 	timer *time.Timer
 	isSet bool
 }
 
-type command int32
-
-const (
-	Set command = iota
-	Unset
-	Quit
-)
-
-// NewThrottleTimer creates a new ThrottleTimer.
 func NewThrottleTimer(name string, dur time.Duration) *ThrottleTimer {
-	c := make(chan struct{})
-	var t = &ThrottleTimer{
-		Name:   name,
-		Ch:     c,
-		dur:    dur,
-		input:  make(chan command),
-		output: c,
-		timer:  time.NewTimer(dur),
-	}
+	var ch = make(chan struct{})
+	var quit = make(chan struct{})
+	var t = &ThrottleTimer{Name: name, Ch: ch, dur: dur, quit: quit}
+	t.mtx.Lock()
+	t.timer = time.AfterFunc(dur, t.fireRoutine)
+	t.mtx.Unlock()
 	t.timer.Stop()
-	go t.run()
 	return t
 }
 
-func (t *ThrottleTimer) run() {
-	for {
-		select {
-		case cmd := <-t.input:
-			// stop goroutine if the input says so
-			// don't close channels, as closed channels mess up select reads
-			if t.processInput(cmd) {
-				return
-			}
-		case <-t.timer.C:
-			t.trySend()
-		}
-	}
-}
-
-// trySend performs non-blocking send on t.Ch
-func (t *ThrottleTimer) trySend() {
+func (t *ThrottleTimer) fireRoutine() {
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
 	select {
-	case t.output <- struct{}{}:
+	case t.Ch <- struct{}{}:
 		t.isSet = false
+	case <-t.quit:
+		// do nothing
 	default:
-		// if we just want to drop, replace this with t.isSet = false
 		t.timer.Reset(t.dur)
 	}
 }
 
-// all modifications of the internal state of ThrottleTimer
-// happen in this method. It is only called from the run goroutine
-// so we avoid any race conditions
-func (t *ThrottleTimer) processInput(cmd command) (shutdown bool) {
-	switch cmd {
-	case Set:
-		if !t.isSet {
-			t.isSet = true
-			t.timer.Reset(t.dur)
-		}
-	case Quit:
-		shutdown = true
-		fallthrough
-	case Unset:
-		if t.isSet {
-			t.isSet = false
-			t.timer.Stop()
-		}
-	default:
-		panic("unknown command!")
-	}
-	return shutdown
-}
-
 func (t *ThrottleTimer) Set() {
-	t.input <- Set
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
+	if !t.isSet {
+		t.isSet = true
+		t.timer.Reset(t.dur)
+	}
 }
 
 func (t *ThrottleTimer) Unset() {
-	t.input <- Unset
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
+	t.isSet = false
+	t.timer.Stop()
 }
 
-// Stop prevents the ThrottleTimer from firing. It always returns true. Stop does not
-// close the channel, to prevent a read from the channel succeeding
-// incorrectly.
-//
-// To prevent a timer created with NewThrottleTimer from firing after a call to
-// Stop, check the return value and drain the channel.
-//
-// For example, assuming the program has not received from t.C already:
-//
-// 	if !t.Stop() {
-// 		<-t.C
-// 	}
-//
-// For ease of stopping services before starting them, we ignore Stop on nil
-// ThrottleTimers.
+// For ease of .Stop()'ing services before .Start()'ing them,
+// we ignore .Stop()'s on nil ThrottleTimers
 func (t *ThrottleTimer) Stop() bool {
 	if t == nil {
 		return false
 	}
-	t.input <- Quit
-	return true
+	close(t.quit)
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
+	return t.timer.Stop()
 }

common/throttle_timer_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 type thCounter struct {
-	input <-chan struct{}
+	input chan struct{}
 	mtx   sync.Mutex
 	count int
 }
@@ -31,9 +31,6 @@ func (c *thCounter) Count() int {
 // Read should run in a go-routine and
 // updates count by one every time a packet comes in
 func (c *thCounter) Read() {
-	// note, since this channel never closes, this will never end
-	// if thCounter was used in anything beyond trivial test cases.
-	// it would have to be smarter.
 	for range c.input {
 		c.Increment()
 	}
@@ -44,7 +41,6 @@ func TestThrottle(test *testing.T) {
 
 	ms := 50
 	delay := time.Duration(ms) * time.Millisecond
-	shortwait := time.Duration(ms/2) * time.Millisecond
 	longwait := time.Duration(2) * delay
 	t := NewThrottleTimer("foo", delay)
 
@@ -69,21 +65,6 @@ func TestThrottle(test *testing.T) {
 	time.Sleep(longwait)
 	assert.Equal(2, c.Count())
 
-	// keep cancelling before it is ready
-	for i := 0; i < 10; i++ {
-		t.Set()
-		time.Sleep(shortwait)
-		t.Unset()
-	}
-	time.Sleep(longwait)
-	assert.Equal(2, c.Count())
-
-	// a few unsets do nothing...
-	for i := 0; i < 5; i++ {
-		t.Unset()
-	}
-	assert.Equal(2, c.Count())
-
 	// send 12, over 2 delay sections, adds 3
 	short := time.Duration(ms/5) * time.Millisecond
 	for i := 0; i < 13; i++ {
@@ -93,6 +74,5 @@ func TestThrottle(test *testing.T) {
 	time.Sleep(longwait)
 	assert.Equal(5, c.Count())
 
-	stopped := t.Stop()
-	assert.True(stopped)
+	close(t.Ch)
 }