From 02e53af36e6c978af692887ed449b74026d76fec Mon Sep 17 00:00:00 2001
From: John Shahid <jvshahid@gmail.com>
Date: Fri, 18 May 2018 15:58:52 -0400
Subject: [PATCH] don't fire twice  when multiple tickers are registered with
 the clock

---
 fakeclock/fake_ticker_test.go | 34 ++++++++++++++++++++++++++++++++++
 fakeclock/fake_timer.go       |  9 ++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/fakeclock/fake_ticker_test.go b/fakeclock/fake_ticker_test.go
index f7ed5a8..874a441 100644
--- a/fakeclock/fake_ticker_test.go
+++ b/fakeclock/fake_ticker_test.go
@@ -1,6 +1,7 @@
 package fakeclock_test
 
 import (
+	"sync/atomic"
 	"time"
 
 	"code.cloudfoundry.org/clock/fakeclock"
@@ -43,6 +44,39 @@ var _ = Describe("FakeTicker", func() {
 		Eventually(timeChan).Should(Receive(Equal(initialTime.Add(30 * time.Second))))
 	})
 
+	It("when there are multiple tickers", func() {
+		const period = 1 * time.Second
+
+		ticker1 := fakeClock.NewTicker(period)
+		ticker2 := fakeClock.NewTicker(period)
+
+		// Eventually(ticker.C()).Should(Recieve) make it hard to detect this error
+		// due to the polling nature of Eventually. We usually end up missing the
+		// second event and it gets dropped on the floor. Use counters instead to
+		// make sure we don't miss the second erroneous event
+		count1 := uint32(0)
+		count2 := uint32(0)
+
+		go func() {
+			for {
+				select {
+				case <-ticker1.C():
+					atomic.AddUint32(&count1, 1)
+				case <-ticker2.C():
+					atomic.AddUint32(&count2, 1)
+				}
+			}
+		}()
+
+		fakeClock.Increment(period)
+
+		Eventually(func() uint32 { return atomic.LoadUint32(&count1) }).Should(BeEquivalentTo(1))
+		Eventually(func() uint32 { return atomic.LoadUint32(&count2) }).Should(BeEquivalentTo(1))
+
+		Consistently(func() uint32 { return atomic.LoadUint32(&count1) }).Should(BeEquivalentTo(1))
+		Consistently(func() uint32 { return atomic.LoadUint32(&count2) }).Should(BeEquivalentTo(1))
+	})
+
 	It("should not fire until a period has passed", func() {
 		const period = 1 * time.Second
 
diff --git a/fakeclock/fake_timer.go b/fakeclock/fake_timer.go
index b412d02..8c6cc0c 100644
--- a/fakeclock/fake_timer.go
+++ b/fakeclock/fake_timer.go
@@ -31,16 +31,19 @@ func (ft *fakeTimer) C() <-chan time.Time {
 	return ft.channel
 }
 
-func (ft *fakeTimer) Reset(d time.Duration) bool {
+func (ft *fakeTimer) reset(d time.Duration) bool {
 	currentTime := ft.clock.Now()
 
 	ft.mutex.Lock()
 	active := !ft.completionTime.IsZero()
 	ft.completionTime = currentTime.Add(d)
 	ft.mutex.Unlock()
+	return active
+}
 
+func (ft *fakeTimer) Reset(d time.Duration) bool {
+	active := ft.reset(d)
 	ft.clock.addTimeWatcher(ft)
-
 	return active
 }
 
@@ -79,6 +82,6 @@ func (ft *fakeTimer) timeUpdated(now time.Time) {
 	}
 
 	if ft.repeatable() {
-		ft.Reset(ft.duration)
+		ft.reset(ft.duration)
 	}
 }