published by bot

(https://github.com/kubernetes/contrib/tree/master/mungegithub)

copied from https://github.com/kubernetes/kubernetes.git, branch master,
last commit is 71ba8a90f0a4f3a307cffeb8f8566d13277cb135

tools/cache/mutation_detector.go

@@ -0,0 +1,135 @@
+/*
+Copyright 2016 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 cache
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"strconv"
+	"sync"
+	"time"
+
+	"k8s.io/client-go/pkg/api"
+	"k8s.io/client-go/pkg/runtime"
+	"k8s.io/client-go/pkg/util/diff"
+)
+
+var mutationDetectionEnabled = false
+
+func init() {
+	mutationDetectionEnabled, _ = strconv.ParseBool(os.Getenv("KUBE_CACHE_MUTATION_DETECTOR"))
+}
+
+type CacheMutationDetector interface {
+	AddObject(obj interface{})
+	Run(stopCh <-chan struct{})
+}
+
+func NewCacheMutationDetector(name string) CacheMutationDetector {
+	if !mutationDetectionEnabled {
+		return dummyMutationDetector{}
+	}
+	return &defaultCacheMutationDetector{name: name, period: 1 * time.Second}
+}
+
+type dummyMutationDetector struct{}
+
+func (dummyMutationDetector) Run(stopCh <-chan struct{}) {
+}
+func (dummyMutationDetector) AddObject(obj interface{}) {
+}
+
+// defaultCacheMutationDetector gives a way to detect if a cached object has been mutated
+// It has a list of cached objects and their copies.  I haven't thought of a way
+// to see WHO is mutating it, just that it's getting mutated.
+type defaultCacheMutationDetector struct {
+	name   string
+	period time.Duration
+
+	lock       sync.Mutex
+	cachedObjs []cacheObj
+
+	// failureFunc is injectable for unit testing.  If you don't have it, the process will panic.
+	// This panic is intentional, since turning on this detection indicates you want a strong
+	// failure signal.  This failure is effectively a p0 bug and you can't trust process results
+	// after a mutation anyway.
+	failureFunc func(message string)
+}
+
+// cacheObj holds the actual object and a copy
+type cacheObj struct {
+	cached interface{}
+	copied interface{}
+}
+
+func (d *defaultCacheMutationDetector) Run(stopCh <-chan struct{}) {
+	// we DON'T want protection from panics.  If we're running this code, we want to die
+	go func() {
+		for {
+			d.CompareObjects()
+
+			select {
+			case <-stopCh:
+				return
+			case <-time.After(d.period):
+			}
+		}
+	}()
+}
+
+// AddObject makes a deep copy of the object for later comparison.  It only works on runtime.Object
+// but that covers the vast majority of our cached objects
+func (d *defaultCacheMutationDetector) AddObject(obj interface{}) {
+	if _, ok := obj.(DeletedFinalStateUnknown); ok {
+		return
+	}
+	if _, ok := obj.(runtime.Object); !ok {
+		return
+	}
+
+	copiedObj, err := api.Scheme.Copy(obj.(runtime.Object))
+	if err != nil {
+		return
+	}
+
+	d.lock.Lock()
+	defer d.lock.Unlock()
+	d.cachedObjs = append(d.cachedObjs, cacheObj{cached: obj, copied: copiedObj})
+}
+
+func (d *defaultCacheMutationDetector) CompareObjects() {
+	d.lock.Lock()
+	defer d.lock.Unlock()
+
+	altered := false
+	for i, obj := range d.cachedObjs {
+		if !reflect.DeepEqual(obj.cached, obj.copied) {
+			fmt.Printf("CACHE %s[%d] ALTERED!\n%v\n", d.name, i, diff.ObjectDiff(obj.cached, obj.copied))
+			altered = true
+		}
+	}
+
+	if altered {
+		msg := fmt.Sprintf("cache %s modified", d.name)
+		if d.failureFunc != nil {
+			d.failureFunc(msg)
+			return
+		}
+		panic(msg)
+	}
+}