Merge pull request #483 from brendandburns/health

Add a caching minion registry.

pkg/registry/caching_minion_registry.go

@@ -0,0 +1,122 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+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 registry
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type Clock interface {
+	Now() time.Time
+}
+
+type SystemClock struct{}
+
+func (SystemClock) Now() time.Time {
+	return time.Now()
+}
+
+type CachingMinionRegistry struct {
+	delegate   MinionRegistry
+	ttl        time.Duration
+	minions    []string
+	lastUpdate int64
+	lock       sync.RWMutex
+	clock      Clock
+}
+
+func NewCachingMinionRegistry(delegate MinionRegistry, ttl time.Duration) (MinionRegistry, error) {
+	list, err := delegate.List()
+	if err != nil {
+		return nil, err
+	}
+	return &CachingMinionRegistry{
+		delegate:   delegate,
+		ttl:        ttl,
+		minions:    list,
+		lastUpdate: time.Now().Unix(),
+		clock:      SystemClock{},
+	}, nil
+}
+
+func (c *CachingMinionRegistry) List() ([]string, error) {
+	if c.expired() {
+		err := c.refresh(false)
+		if err != nil {
+			return c.minions, err
+		}
+	}
+	return c.minions, nil
+}
+
+func (c *CachingMinionRegistry) Insert(minion string) error {
+	err := c.delegate.Insert(minion)
+	if err != nil {
+		return err
+	}
+	return c.refresh(true)
+}
+
+func (c *CachingMinionRegistry) Delete(minion string) error {
+	err := c.delegate.Delete(minion)
+	if err != nil {
+		return err
+	}
+	return c.refresh(true)
+}
+
+func (c *CachingMinionRegistry) Contains(minion string) (bool, error) {
+	if c.expired() {
+		err := c.refresh(false)
+		if err != nil {
+			return false, err
+		}
+	}
+
+	// block updates in the middle of a contains.
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	for _, name := range c.minions {
+		if name == minion {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// refresh updates the current store.  It double checks expired under lock with the assumption
+// of optimistic concurrency with the other functions.
+func (c *CachingMinionRegistry) refresh(force bool) error {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	if force || c.expired() {
+		var err error
+		c.minions, err = c.delegate.List()
+		time := c.clock.Now()
+		atomic.SwapInt64(&c.lastUpdate, time.Unix())
+		return err
+	}
+	return nil
+}
+
+func (c *CachingMinionRegistry) expired() bool {
+	var unix int64
+	atomic.SwapInt64(&unix, c.lastUpdate)
+	return c.clock.Now().Sub(time.Unix(c.lastUpdate, 0)) > c.ttl
+}

pkg/registry/caching_minion_registry_test.go

@@ -0,0 +1,116 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+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 registry
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+type fakeClock struct {
+	now time.Time
+}
+
+func (f *fakeClock) Now() time.Time {
+	return f.now
+}
+
+func TestCachingHit(t *testing.T) {
+	fakeClock := fakeClock{
+		now: time.Unix(0, 0),
+	}
+	fakeRegistry := MakeMockMinionRegistry([]string{"m1", "m2"})
+	expected := []string{"m1", "m2", "m3"}
+	cache := CachingMinionRegistry{
+		delegate:   fakeRegistry,
+		ttl:        1 * time.Second,
+		clock:      &fakeClock,
+		lastUpdate: fakeClock.Now().Unix(),
+		minions:    expected,
+	}
+	list, err := cache.List()
+	expectNoError(t, err)
+	if !reflect.DeepEqual(list, expected) {
+		t.Errorf("expected: %v, got %v", expected, list)
+	}
+}
+
+func TestCachingMiss(t *testing.T) {
+	fakeClock := fakeClock{
+		now: time.Unix(0, 0),
+	}
+	fakeRegistry := MakeMockMinionRegistry([]string{"m1", "m2"})
+	expected := []string{"m1", "m2", "m3"}
+	cache := CachingMinionRegistry{
+		delegate:   fakeRegistry,
+		ttl:        1 * time.Second,
+		clock:      &fakeClock,
+		lastUpdate: fakeClock.Now().Unix(),
+		minions:    expected,
+	}
+	fakeClock.now = time.Unix(3, 0)
+	list, err := cache.List()
+	expectNoError(t, err)
+	if !reflect.DeepEqual(list, fakeRegistry.minions) {
+		t.Errorf("expected: %v, got %v", fakeRegistry.minions, list)
+	}
+}
+
+func TestCachingInsert(t *testing.T) {
+	fakeClock := fakeClock{
+		now: time.Unix(0, 0),
+	}
+	fakeRegistry := MakeMockMinionRegistry([]string{"m1", "m2"})
+	expected := []string{"m1", "m2", "m3"}
+	cache := CachingMinionRegistry{
+		delegate:   fakeRegistry,
+		ttl:        1 * time.Second,
+		clock:      &fakeClock,
+		lastUpdate: fakeClock.Now().Unix(),
+		minions:    expected,
+	}
+	err := cache.Insert("foo")
+	expectNoError(t, err)
+	list, err := cache.List()
+	expectNoError(t, err)
+	if !reflect.DeepEqual(list, fakeRegistry.minions) {
+		t.Errorf("expected: %v, got %v", fakeRegistry.minions, list)
+	}
+}
+
+func TestCachingDelete(t *testing.T) {
+	fakeClock := fakeClock{
+		now: time.Unix(0, 0),
+	}
+	fakeRegistry := MakeMockMinionRegistry([]string{"m1", "m2"})
+	expected := []string{"m1", "m2", "m3"}
+	cache := CachingMinionRegistry{
+		delegate:   fakeRegistry,
+		ttl:        1 * time.Second,
+		clock:      &fakeClock,
+		lastUpdate: fakeClock.Now().Unix(),
+		minions:    expected,
+	}
+	err := cache.Delete("m2")
+	expectNoError(t, err)
+	list, err := cache.List()
+	expectNoError(t, err)
+	if !reflect.DeepEqual(list, fakeRegistry.minions) {
+		t.Errorf("expected: %v, got %v", fakeRegistry.minions, list)
+	}
+}