Merge branch 'upstream-mirror' into sync-updates

# Conflicts:
#	layeredcache_test.go

Makefile

@@ -1,5 +1,5 @@
 t:
-	go test ./...
+	go test ./... -race -count=1
 
 f:
 	go fmt ./...

cache.go

@@ -141,6 +141,9 @@ func (c *Cache) Replace(key string, value interface{}) bool {
 // Attempts to get the value from the cache and calles fetch on a miss (missing
 // or stale item). If fetch returns an error, no value is cached and the error
 // is returned back to the caller.
+// Note that Fetch merely calls the public Get and Set functions. If you want
+// a different Fetch behavior, such as thundering herd protection or returning
+// expired items, implement it in your application.
 func (c *Cache) Fetch(key string, duration time.Duration, fetch func() (interface{}, error)) (*Item, error) {
 	item := c.Get(key)
 	if item != nil && !item.Expired() {
@@ -373,7 +376,13 @@ func (c *Cache) doPromote(item *Item) bool {
 func (c *Cache) gc() int {
 	dropped := 0
 	element := c.list.Back()
-	for i := 0; i < c.itemsToPrune; i++ {
+
+	itemsToPrune := int64(c.itemsToPrune)
+	if min := c.size - c.maxSize; min > itemsToPrune {
+		itemsToPrune = min
+	}
+
+	for i := int64(0); i < itemsToPrune; i++ {
 		if element == nil {
 			return dropped
 		}

cache_test.go

@@ -18,6 +18,7 @@ func Test_Cache(t *testing.T) {
 
 func (_ CacheTests) DeletesAValue() {
 	cache := New(Configure())
+	defer cache.Stop()
 	Expect(cache.ItemCount()).To.Equal(0)
 
 	cache.Set("spice", "flow", time.Minute)
@@ -32,6 +33,7 @@ func (_ CacheTests) DeletesAValue() {
 
 func (_ CacheTests) DeletesAPrefix() {
 	cache := New(Configure())
+	defer cache.Stop()
 	Expect(cache.ItemCount()).To.Equal(0)
 
 	cache.Set("aaa", "1", time.Minute)
@@ -55,6 +57,7 @@ func (_ CacheTests) DeletesAPrefix() {
 
 func (_ CacheTests) DeletesAFunc() {
 	cache := New(Configure())
+	defer cache.Stop()
 	Expect(cache.ItemCount()).To.Equal(0)
 
 	cache.Set("a", 1, time.Minute)

go.mod

@@ -3,6 +3,6 @@ module github.com/karlseguin/ccache/v2
 go 1.13
 
 require (
-	github.com/karlseguin/expect v1.0.2-0.20190806010014-778a5f0c6003
+	github.com/karlseguin/expect v1.0.7
 	github.com/wsxiaoys/terminal v0.0.0-20160513160801-0940f3fc43a0
 )

go.sum

@@ -2,5 +2,7 @@ github.com/karlseguin/expect v1.0.1 h1:z4wy4npwwHSWKjGWH85WNJO42VQhovxTCZDSzhjo8
 github.com/karlseguin/expect v1.0.1/go.mod h1:zNBxMY8P21owkeogJELCLeHIt+voOSduHYTFUbwRAV8=
 github.com/karlseguin/expect v1.0.2-0.20190806010014-778a5f0c6003 h1:vJ0Snvo+SLMY72r5J4sEfkuE7AFbixEP2qRbEcum/wA=
 github.com/karlseguin/expect v1.0.2-0.20190806010014-778a5f0c6003/go.mod h1:zNBxMY8P21owkeogJELCLeHIt+voOSduHYTFUbwRAV8=
+github.com/karlseguin/expect v1.0.7 h1:OF4mqjblc450v8nKARBS5Q0AweBNR0A+O3VjjpxwBrg=
+github.com/karlseguin/expect v1.0.7/go.mod h1:lXdI8iGiQhmzpnnmU/EGA60vqKs8NbRNFnhhrJGoD5g=
 github.com/wsxiaoys/terminal v0.0.0-20160513160801-0940f3fc43a0 h1:3UeQBvD0TFrlVjOeLOBz+CPAI8dnbqNSVwUwRrkp7vQ=
 github.com/wsxiaoys/terminal v0.0.0-20160513160801-0940f3fc43a0/go.mod h1:IXCdmsXIht47RaVFLEdVnh1t+pgYtTAhQGj73kz+2DM=

layeredcache.go

@@ -131,6 +131,9 @@ func (c *LayeredCache) Replace(primary, secondary string, value interface{}) boo
 // Attempts to get the value from the cache and calles fetch on a miss.
 // If fetch returns an error, no value is cached and the error is returned back
 // to the caller.
+// Note that Fetch merely calls the public Get and Set functions. If you want
+// a different Fetch behavior, such as thundering herd protection or returning
+// expired items, implement it in your application.
 func (c *LayeredCache) Fetch(primary, secondary string, duration time.Duration, fetch func() (interface{}, error)) (*Item, error) {
 	item := c.Get(primary, secondary)
 	if item != nil {
@@ -297,7 +300,13 @@ func (c *LayeredCache) doPromote(item *Item) bool {
 func (c *LayeredCache) gc() int {
 	element := c.list.Back()
 	dropped := 0
-	for i := 0; i < c.itemsToPrune; i++ {
+	itemsToPrune := int64(c.itemsToPrune)
+
+	if min := c.size - c.maxSize; min > itemsToPrune {
+		itemsToPrune = min
+	}
+
+	for i := int64(0); i < itemsToPrune; i++ {
 		if element == nil {
 			return dropped
 		}

layeredcache_test.go

@@ -235,6 +235,8 @@ func (_ LayeredCacheTests) ResizeOnTheFly() {
 	for i := 0; i < 5; i++ {
 		cache.Set(strconv.Itoa(i), "a", i, time.Minute)
 	}
+	cache.SyncUpdates()
+
 	cache.SetMaxSize(3)
 	cache.SyncUpdates()
 	Expect(cache.GetDropped()).To.Equal(2)

readme.md

@@ -86,6 +86,8 @@ item, err := cache.Fetch("user:4", time.Minute * 10, func() (interface{}, error)
 })
 ```
 
+`Fetch` doesn't do anything fancy: it merely uses the public `Get` and `Set` functions. If you want more advanced behavior, such as using a singleflight to protect against thundering herd, support a callback that accepts the key, or returning expired items, you should implement that in your application. 
+
 ### Delete
 `Delete` expects the key to delete. It's ok to call `Delete` on a non-existent key: