[scheduler] interface for configuration factory, configurator.

plugin/pkg/scheduler/util/backoff_utils.go

@@ -0,0 +1,135 @@
+/*
+Copyright 2017 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 util
+
+import (
+	"fmt"
+	"github.com/golang/glog"
+	ktypes "k8s.io/apimachinery/pkg/types"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type clock interface {
+	Now() time.Time
+}
+
+type realClock struct{}
+
+func (realClock) Now() time.Time {
+	return time.Now()
+}
+
+// backoffEntry is single threaded.  in particular, it only allows a single action to be waiting on backoff at a time.
+// It is expected that all users will only use the public TryWait(...) method
+// It is also not safe to copy this object.
+type backoffEntry struct {
+	backoff     time.Duration
+	lastUpdate  time.Time
+	reqInFlight int32
+}
+
+// tryLock attempts to acquire a lock via atomic compare and swap.
+// returns true if the lock was acquired, false otherwise
+func (b *backoffEntry) tryLock() bool {
+	return atomic.CompareAndSwapInt32(&b.reqInFlight, 0, 1)
+}
+
+// unlock returns the lock.  panics if the lock isn't held
+func (b *backoffEntry) unlock() {
+	if !atomic.CompareAndSwapInt32(&b.reqInFlight, 1, 0) {
+		panic(fmt.Sprintf("unexpected state on unlocking: %+v", b))
+	}
+}
+
+// TryWait tries to acquire the backoff lock, maxDuration is the maximum allowed period to wait for.
+func (b *backoffEntry) TryWait(maxDuration time.Duration) bool {
+	if !b.tryLock() {
+		return false
+	}
+	defer b.unlock()
+	b.wait(maxDuration)
+	return true
+}
+
+func (entry *backoffEntry) getBackoff(maxDuration time.Duration) time.Duration {
+	duration := entry.backoff
+	newDuration := time.Duration(duration) * 2
+	if newDuration > maxDuration {
+		newDuration = maxDuration
+	}
+	entry.backoff = newDuration
+	glog.V(4).Infof("Backing off %s for pod %+v", duration.String(), entry)
+	return duration
+}
+
+func (entry *backoffEntry) wait(maxDuration time.Duration) {
+	time.Sleep(entry.getBackoff(maxDuration))
+}
+
+type PodBackoff struct {
+	perPodBackoff   map[ktypes.NamespacedName]*backoffEntry
+	lock            sync.Mutex
+	clock           clock
+	defaultDuration time.Duration
+	maxDuration     time.Duration
+}
+
+func (p *PodBackoff) MaxDuration() time.Duration {
+	return p.maxDuration
+}
+
+func CreateDefaultPodBackoff() *PodBackoff {
+	return CreatePodBackoff(1*time.Second, 60*time.Second)
+}
+
+func CreatePodBackoff(defaultDuration, maxDuration time.Duration) *PodBackoff {
+	return CreatePodBackoffWithClock(defaultDuration, maxDuration, realClock{})
+}
+
+func CreatePodBackoffWithClock(defaultDuration, maxDuration time.Duration, clock clock) *PodBackoff {
+	return &PodBackoff{
+		perPodBackoff:   map[ktypes.NamespacedName]*backoffEntry{},
+		clock:           clock,
+		defaultDuration: defaultDuration,
+		maxDuration:     maxDuration,
+	}
+}
+
+func (p *PodBackoff) GetEntry(podID ktypes.NamespacedName) *backoffEntry {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	entry, ok := p.perPodBackoff[podID]
+	if !ok {
+		entry = &backoffEntry{backoff: p.defaultDuration}
+		p.perPodBackoff[podID] = entry
+	}
+	entry.lastUpdate = p.clock.Now()
+	return entry
+}
+
+func (p *PodBackoff) Gc() {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	now := p.clock.Now()
+	for podID, entry := range p.perPodBackoff {
+		if now.Sub(entry.lastUpdate) > p.maxDuration {
+			delete(p.perPodBackoff, podID)
+		}
+	}
+}