Using a fixed set of locks, then we don't need to free unused locks

anymore.
See kubernetes/kubernetes/pull/66442 for discussions.

hack/.golint_failures

@@ -357,7 +357,6 @@ pkg/util/initsystem
 pkg/util/ipconfig
 pkg/util/iptables
 pkg/util/iptables/testing
-pkg/util/keymutex
 pkg/util/labels
 pkg/util/mount
 pkg/util/netsh/testing

pkg/util/keymutex/BUILD

@@ -8,7 +8,10 @@ load(
 
 go_library(
     name = "go_default_library",
-    srcs = ["keymutex.go"],
+    srcs = [
+        "hashed.go",
+        "keymutex.go",
+    ],
     importpath = "k8s.io/kubernetes/pkg/util/keymutex",
     deps = ["//vendor/github.com/golang/glog:go_default_library"],
 )

pkg/util/keymutex/hashed.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package keymutex
+
+import (
+	"hash/fnv"
+	"runtime"
+	"sync"
+
+	"github.com/golang/glog"
+)
+
+// NewHashed returns a new instance of KeyMutex which hashes arbitrary keys to
+// a fixed set of locks. `n` specifies number of locks, if n <= 0, we use
+// number of cpus.
+// Note that because it uses fixed set of locks, different keys may share same
+// lock, so it's possible to wait on same lock.
+func NewHashed(n int) KeyMutex {
+	if n <= 0 {
+		n = runtime.NumCPU()
+	}
+	return &hashedKeyMutex{
+		mutexes: make([]sync.Mutex, n),
+	}
+}
+
+type hashedKeyMutex struct {
+	mutexes []sync.Mutex
+}
+
+// Acquires a lock associated with the specified ID.
+func (km *hashedKeyMutex) LockKey(id string) {
+	glog.V(5).Infof("hashedKeyMutex.LockKey(...) called for id %q\r\n", id)
+	km.mutexes[km.hash(id)%len(km.mutexes)].Lock()
+	glog.V(5).Infof("hashedKeyMutex.LockKey(...) for id %q completed.\r\n", id)
+}
+
+// Releases the lock associated with the specified ID.
+func (km *hashedKeyMutex) UnlockKey(id string) error {
+	glog.V(5).Infof("hashedKeyMutex.UnlockKey(...) called for id %q\r\n", id)
+	km.mutexes[km.hash(id)%len(km.mutexes)].Unlock()
+	glog.V(5).Infof("hashedKeyMutex.UnlockKey(...) for id %q completed.\r\n", id)
+	return nil
+}
+
+func (km *hashedKeyMutex) hash(id string) int {
+	h := fnv.New32a()
+	h.Write([]byte(id))
+	return int(h.Sum32())
+}

pkg/util/keymutex/keymutex.go

@@ -16,13 +16,6 @@ limitations under the License.
 
 package keymutex
 
-import (
-	"fmt"
-	"sync"
-
-	"github.com/golang/glog"
-)
-
 // KeyMutex is a thread-safe interface for acquiring locks on arbitrary strings.
 type KeyMutex interface {
 	// Acquires a lock associated with the specified ID, creates the lock if one doesn't already exist.
@@ -32,52 +25,3 @@ type KeyMutex interface {
 	// Returns an error if the specified ID doesn't exist.
 	UnlockKey(id string) error
 }
-
-// Returns a new instance of a key mutex.
-func NewKeyMutex() KeyMutex {
-	return &keyMutex{
-		mutexMap: make(map[string]*sync.Mutex),
-	}
-}
-
-type keyMutex struct {
-	sync.RWMutex
-	mutexMap map[string]*sync.Mutex
-}
-
-// Acquires a lock associated with the specified ID (creates the lock if one doesn't already exist).
-func (km *keyMutex) LockKey(id string) {
-	glog.V(5).Infof("LockKey(...) called for id %q\r\n", id)
-	mutex := km.getOrCreateLock(id)
-	mutex.Lock()
-	glog.V(5).Infof("LockKey(...) for id %q completed.\r\n", id)
-}
-
-// Releases the lock associated with the specified ID.
-// Returns an error if the specified ID doesn't exist.
-func (km *keyMutex) UnlockKey(id string) error {
-	glog.V(5).Infof("UnlockKey(...) called for id %q\r\n", id)
-	km.RLock()
-	defer km.RUnlock()
-	mutex, exists := km.mutexMap[id]
-	if !exists {
-		return fmt.Errorf("id %q not found", id)
-	}
-	glog.V(5).Infof("UnlockKey(...) for id. Mutex found, trying to unlock it. %q\r\n", id)
-
-	mutex.Unlock()
-	glog.V(5).Infof("UnlockKey(...) for id %q completed.\r\n", id)
-	return nil
-}
-
-// Returns lock associated with the specified ID, or creates the lock if one doesn't already exist.
-func (km *keyMutex) getOrCreateLock(id string) *sync.Mutex {
-	km.Lock()
-	defer km.Unlock()
-
-	if _, exists := km.mutexMap[id]; !exists {
-		km.mutexMap[id] = &sync.Mutex{}
-	}
-
-	return km.mutexMap[id]
-}

pkg/util/keymutex/keymutex_test.go

@@ -25,9 +25,18 @@ const (
 	callbackTimeout = 1 * time.Second
 )
 
+func newKeyMutexes() []KeyMutex {
+	return []KeyMutex{
+		NewHashed(0),
+		NewHashed(1),
+		NewHashed(2),
+		NewHashed(4),
+	}
+}
+
 func Test_SingleLock_NoUnlock(t *testing.T) {
+	for _, km := range newKeyMutexes() {
 		// Arrange
-	km := NewKeyMutex()
 		key := "fakeid"
 		callbackCh := make(chan interface{})
 
@@ -36,11 +45,12 @@ func Test_SingleLock_NoUnlock(t *testing.T) {
 
 		// Assert
 		verifyCallbackHappens(t, callbackCh)
+	}
 }
 
 func Test_SingleLock_SingleUnlock(t *testing.T) {
+	for _, km := range newKeyMutexes() {
 		// Arrange
-	km := NewKeyMutex()
 		key := "fakeid"
 		callbackCh := make(chan interface{})
 
@@ -48,11 +58,12 @@ func Test_SingleLock_SingleUnlock(t *testing.T) {
 		go lockAndCallback(km, key, callbackCh)
 		verifyCallbackHappens(t, callbackCh)
 		km.UnlockKey(key)
+	}
 }
 
 func Test_DoubleLock_DoubleUnlock(t *testing.T) {
+	for _, km := range newKeyMutexes() {
 		// Arrange
-	km := NewKeyMutex()
 		key := "fakeid"
 		callbackCh1stLock := make(chan interface{})
 		callbackCh2ndLock := make(chan interface{})
@@ -65,6 +76,7 @@ func Test_DoubleLock_DoubleUnlock(t *testing.T) {
 		km.UnlockKey(key)
 		verifyCallbackHappens(t, callbackCh2ndLock)
 		km.UnlockKey(key)
+	}
 }
 
 func lockAndCallback(km KeyMutex, id string, callbackCh chan<- interface{}) {

pkg/volume/azure_dd/attacher.go

@@ -53,7 +53,7 @@ var _ volume.Attacher = &azureDiskAttacher{}
 var _ volume.Detacher = &azureDiskDetacher{}
 
 // acquire lock to get an lun number
-var getLunMutex = keymutex.NewKeyMutex()
+var getLunMutex = keymutex.NewHashed(0)
 
 // Attach attaches a volume.Spec to an Azure VM referenced by NodeName, returning the disk's LUN
 func (a *azureDiskAttacher) Attach(spec *volume.Spec, nodeName types.NodeName) (string, error) {

pkg/volume/cinder/cinder.go

@@ -87,7 +87,7 @@ func getPath(uid types.UID, volName string, host volume.VolumeHost) string {
 
 func (plugin *cinderPlugin) Init(host volume.VolumeHost) error {
 	plugin.host = host
-	plugin.volumeLocks = keymutex.NewKeyMutex()
+	plugin.volumeLocks = keymutex.NewHashed(0)
 	return nil
 }
 

pkg/volume/iscsi/iscsi.go

@@ -55,7 +55,7 @@ const (
 
 func (plugin *iscsiPlugin) Init(host volume.VolumeHost) error {
 	plugin.host = host
-	plugin.targetLocks = keymutex.NewKeyMutex()
+	plugin.targetLocks = keymutex.NewHashed(0)
 	return nil
 }
 

pkg/volume/local/local.go

@@ -59,7 +59,7 @@ const (
 
 func (plugin *localVolumePlugin) Init(host volume.VolumeHost) error {
 	plugin.host = host
-	plugin.volumeLocks = keymutex.NewKeyMutex()
+	plugin.volumeLocks = keymutex.NewHashed(0)
 	plugin.recorder = host.GetEventRecorder()
 	return nil
 }

pkg/volume/scaleio/sio_plugin.go

@@ -50,7 +50,7 @@ var _ volume.VolumePlugin = &sioPlugin{}
 
 func (p *sioPlugin) Init(host volume.VolumeHost) error {
 	p.host = host
-	p.volumeMtx = keymutex.NewKeyMutex()
+	p.volumeMtx = keymutex.NewHashed(0)
 	return nil
 }
 

pkg/volume/vsphere_volume/attacher.go

@@ -41,7 +41,7 @@ var _ volume.Attacher = &vsphereVMDKAttacher{}
 var _ volume.AttachableVolumePlugin = &vsphereVolumePlugin{}
 
 // Singleton key mutex for keeping attach operations for the same host atomic
-var attachdetachMutex = keymutex.NewKeyMutex()
+var attachdetachMutex = keymutex.NewHashed(0)
 
 func (plugin *vsphereVolumePlugin) NewAttacher() (volume.Attacher, error) {
 	vsphereCloud, err := getCloudProvider(plugin.host.GetCloudProvider())