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ClusterCacheTracker: non-blocking per-cluster locking
Co-authored-by: Florian Gutmann <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| /* | ||
| Copyright 2021 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. | ||
| */ | ||
|
|
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| package remote | ||
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| import "sync" | ||
|
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||
| // keyedMutex is a mutex locking on the key provided to the Lock function. | ||
| // Only one caller can hold the lock for a specific key at a time. | ||
| // A second Lock call if the lock is already held for a key returns false. | ||
| type keyedMutex struct { | ||
| locksMtx sync.Mutex | ||
| locks map[interface{}]*sync.Mutex | ||
| } | ||
|
|
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| // newKeyedMutex creates a new keyed mutex ready for use. | ||
| func newKeyedMutex() *keyedMutex { | ||
| return &keyedMutex{ | ||
| locks: make(map[interface{}]*sync.Mutex), | ||
| } | ||
| } | ||
|
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| // unlock unlocks a currently locked key. | ||
| type unlock func() | ||
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| // TryLock locks the passed in key if it's not already locked. | ||
| // Returns the unlock function to release the lock on the key. | ||
| // A second Lock call if the lock is already held for a key returns false. | ||
| // In the ClusterCacheTracker case the key is the ObjectKey for a cluster. | ||
| func (k *keyedMutex) TryLock(key interface{}) (unlock, bool) { | ||
| // Get the lock if it doesn't exist already. | ||
| // If it does exist, return false. | ||
| l, ok := func() (*sync.Mutex, bool) { | ||
| k.locksMtx.Lock() | ||
| defer k.locksMtx.Unlock() | ||
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| l, ok := k.locks[key] | ||
| if !ok { | ||
| // Lock doesn't exist yet, create one and return it. | ||
| l = &sync.Mutex{} | ||
| k.locks[key] = l | ||
| return l, true | ||
| } | ||
|
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| // Lock already exists, return false. | ||
| return nil, false | ||
| }() | ||
|
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| // Return false if another go routine already holds the lock for this key (e.g. Cluster). | ||
| if !ok { | ||
| return nil, false | ||
| } | ||
|
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| // Lock for the current key (e.g. Cluster). | ||
| l.Lock() | ||
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| // Unlock the key (e.g. Cluster) and remove it from the lock map. | ||
| return func() { | ||
| k.locksMtx.Lock() | ||
| defer k.locksMtx.Unlock() | ||
|
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| l.Unlock() | ||
| delete(k.locks, key) | ||
| }, true | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| /* | ||
| Copyright 2021 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. | ||
| */ | ||
|
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||
| package remote | ||
|
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| import ( | ||
| "testing" | ||
|
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| . "github.com/onsi/gomega" | ||
| metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" | ||
| "sigs.k8s.io/controller-runtime/pkg/client" | ||
| ) | ||
|
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| func TestKeyedMutex(t *testing.T) { | ||
| t.Run("Lock a Cluster and ensures the second Lock on the same Cluster returns false", func(t *testing.T) { | ||
| t.Parallel() | ||
| g := NewWithT(t) | ||
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| cluster1 := client.ObjectKey{Namespace: metav1.NamespaceDefault, Name: "Cluster1"} | ||
| km := newKeyedMutex() | ||
|
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| // Try to lock cluster1. | ||
| // Should work as nobody currently holds the lock for cluster1. | ||
| unlock, ok := km.TryLock(cluster1) | ||
| g.Expect(ok).To(BeTrue()) | ||
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| // Try to lock cluster1 again. | ||
| // Shouldn't work as cluster1 is already locked. | ||
| _, ok = km.TryLock(cluster1) | ||
| g.Expect(ok).To(BeFalse()) | ||
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| // Unlock cluster1. | ||
| unlock() | ||
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| // Ensure that the lock was cleaned up from the internal map. | ||
| g.Expect(km.locks).To(HaveLen(0)) | ||
| }) | ||
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| t.Run("Can lock different Clusters in parallel but each one only once", func(t *testing.T) { | ||
| g := NewWithT(t) | ||
| km := newKeyedMutex() | ||
| clusters := []client.ObjectKey{ | ||
| {Namespace: metav1.NamespaceDefault, Name: "Cluster1"}, | ||
| {Namespace: metav1.NamespaceDefault, Name: "Cluster2"}, | ||
| {Namespace: metav1.NamespaceDefault, Name: "Cluster3"}, | ||
| {Namespace: metav1.NamespaceDefault, Name: "Cluster4"}, | ||
| } | ||
|
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| // Run this twice to ensure Clusters can be locked again | ||
| // after they have been unlocked. | ||
| for i := 0; i < 2; i++ { | ||
| unlocks := make([]unlock, 0, len(clusters)) | ||
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| // Lock all Clusters (should work). | ||
| for _, key := range clusters { | ||
| unlock, ok := km.TryLock(key) | ||
| g.Expect(ok).To(BeTrue()) | ||
| unlocks = append(unlocks, unlock) | ||
| } | ||
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| // Ensure Clusters can't be locked again. | ||
| for _, key := range clusters { | ||
| _, ok := km.TryLock(key) | ||
| g.Expect(ok).To(BeFalse()) | ||
| } | ||
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| // Unlock all Clusters. | ||
| for _, unlock := range unlocks { | ||
| unlock() | ||
| } | ||
| } | ||
|
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| // Ensure that the lock was cleaned up from the internal map. | ||
| g.Expect(km.locks).To(HaveLen(0)) | ||
| }) | ||
| } |
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