cache: make Stop() synchronous and races in tests

worker goroutine running concurrently with tests would cause data race errors
when running tests with -race enabled.

cache.go

@@ -16,6 +16,7 @@ type Cache struct {
 	bucketMask  uint32
 	deletables  chan *Item
 	promotables chan *Item
+	donec       chan struct{}
 }
 
 // Create a new cache with the specified configuration
@@ -26,15 +27,13 @@ func New(config *Configuration) *Cache {
 		Configuration: config,
 		bucketMask:    uint32(config.buckets) - 1,
 		buckets:       make([]*bucket, config.buckets),
-		deletables:    make(chan *Item, config.deleteBuffer),
-		promotables:   make(chan *Item, config.promoteBuffer),
 	}
 	for i := 0; i < int(config.buckets); i++ {
 		c.buckets[i] = &bucket{
 			lookup: make(map[string]*Item),
 		}
 	}
-	go c.worker()
+	c.restart()
 	return c
 }
 
@@ -119,6 +118,14 @@ func (c *Cache) Clear() {
 // is called are likely to panic
 func (c *Cache) Stop() {
 	close(c.promotables)
+	<-c.donec
+}
+
+func (c *Cache) restart() {
+	c.deletables = make(chan *Item, c.deleteBuffer)
+	c.promotables = make(chan *Item, c.promoteBuffer)
+	c.donec = make(chan struct{})
+	go c.worker()
 }
 
 func (c *Cache) deleteItem(bucket *bucket, item *Item) {
@@ -146,6 +153,8 @@ func (c *Cache) promote(item *Item) {
 }
 
 func (c *Cache) worker() {
+	defer close(c.donec)
+
 	for {
 		select {
 		case item, ok := <-c.promotables:

cache_test.go

@@ -41,7 +41,7 @@ func (_ CacheTests) GCsTheOldestItems() {
 	}
 	//let the items get promoted (and added to our list)
 	time.Sleep(time.Millisecond * 10)
-	cache.gc()
+	gcCache(cache)
 	Expect(cache.Get("9")).To.Equal(nil)
 	Expect(cache.Get("10").Value()).To.Equal(10)
 }
@@ -54,7 +54,7 @@ func (_ CacheTests) PromotedItemsDontGetPruned() {
 	time.Sleep(time.Millisecond * 10) //run the worker once to init the list
 	cache.Get("9")
 	time.Sleep(time.Millisecond * 10)
-	cache.gc()
+	gcCache(cache)
 	Expect(cache.Get("9").Value()).To.Equal(9)
 	Expect(cache.Get("10")).To.Equal(nil)
 	Expect(cache.Get("11").Value()).To.Equal(11)
@@ -67,11 +67,11 @@ func (_ CacheTests) TrackerDoesNotCleanupHeldInstance() {
 	}
 	item := cache.TrackingGet("0")
 	time.Sleep(time.Millisecond * 10)
-	cache.gc()
+	gcCache(cache)
 	Expect(cache.Get("0").Value()).To.Equal(0)
 	Expect(cache.Get("1")).To.Equal(nil)
 	item.Release()
-	cache.gc()
+	gcCache(cache)
 	Expect(cache.Get("0")).To.Equal(nil)
 }
 
@@ -104,19 +104,19 @@ func (_ CacheTests) SetUpdatesSizeOnDelta() {
 	cache.Set("a", &SizedItem{0, 2}, time.Minute)
 	cache.Set("b", &SizedItem{0, 3}, time.Minute)
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(5))
+	checkSize(cache, 5)
 	cache.Set("b", &SizedItem{0, 3}, time.Minute)
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(5))
+	checkSize(cache, 5)
 	cache.Set("b", &SizedItem{0, 4}, time.Minute)
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(6))
+	checkSize(cache, 6)
 	cache.Set("b", &SizedItem{0, 2}, time.Minute)
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(4))
+	checkSize(cache, 4)
 	cache.Delete("b")
 	time.Sleep(time.Millisecond * 100)
-	Expect(cache.size).To.Equal(int64(2))
+	checkSize(cache, 2)
 }
 
 func (_ CacheTests) ReplaceDoesNotchangeSizeIfNotSet() {
@@ -126,7 +126,7 @@ func (_ CacheTests) ReplaceDoesNotchangeSizeIfNotSet() {
 	cache.Set("3", &SizedItem{1, 2}, time.Minute)
 	cache.Replace("4", &SizedItem{1, 2})
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(6))
+	checkSize(cache, 6)
 }
 
 func (_ CacheTests) ReplaceChangesSize() {
@@ -136,15 +136,15 @@ func (_ CacheTests) ReplaceChangesSize() {
 
 	cache.Replace("2", &SizedItem{1, 2})
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(4))
+	checkSize(cache, 4)
 
 	cache.Replace("2", &SizedItem{1, 1})
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(3))
+	checkSize(cache, 3)
 
 	cache.Replace("2", &SizedItem{1, 3})
 	time.Sleep(time.Millisecond * 5)
-	Expect(cache.size).To.Equal(int64(5))
+	checkSize(cache, 5)
 }
 
 type SizedItem struct {
@@ -155,3 +155,15 @@ type SizedItem struct {
 func (s *SizedItem) Size() int64 {
 	return s.s
 }
+
+func checkSize(cache *Cache, sz int64) {
+	cache.Stop()
+	Expect(cache.size).To.Equal(sz)
+	cache.restart()
+}
+
+func gcCache(cache *Cache) {
+	cache.Stop()
+	cache.gc()
+	cache.restart()
+}