genericize ip cache

pkg/master/ip_cache.go

@@ -17,7 +17,6 @@ limitations under the License.
 package master
 
 import (
-	"sync"
 	"time"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider"
@@ -26,19 +25,6 @@ import (
 	"github.com/golang/glog"
 )
 
-type ipCacheEntry struct {
-	ip         string
-	lastUpdate time.Time
-}
-
-type ipCache struct {
-	clock         util.Clock
-	cloudProvider cloudprovider.Interface
-	cache         map[string]ipCacheEntry
-	lock          sync.Mutex
-	ttl           time.Duration
-}
-
 // NewIPCache makes a new ip caching layer, which will get IP addresses from cp,
 // and use clock for deciding when to re-get an IP address.
 // Thread-safe.
@@ -47,30 +33,24 @@ type ipCache struct {
 // that could be produced from a template and a type via `go generate`.
 func NewIPCache(cp cloudprovider.Interface, clock util.Clock, ttl time.Duration) *ipCache {
 	return &ipCache{
-		clock:         clock,
-		cloudProvider: cp,
-		cache:         map[string]ipCacheEntry{},
-		ttl:           ttl,
+		cache: util.NewTimeCache(
+			clock,
+			ttl,
+			func(host string) util.T {
+				return getInstanceIPFromCloud(cp, host)
+			},
+		),
 	}
 }
 
+type ipCache struct {
+	cache util.TimeCache
+}
+
 // GetInstanceIP returns the IP address of host, from the cache
 // if possible, otherwise it asks the cloud provider.
 func (c *ipCache) GetInstanceIP(host string) string {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	data, ok := c.cache[host]
-	now := c.clock.Now()
-
-	if !ok || now.Sub(data.lastUpdate) > c.ttl {
-		ip := getInstanceIPFromCloud(c.cloudProvider, host)
-		data = ipCacheEntry{
-			ip:         ip,
-			lastUpdate: now,
-		}
-		c.cache[host] = data
-	}
-	return data.ip
+	return c.cache.Get(host).(string)
 }
 
 func getInstanceIPFromCloud(cloud cloudprovider.Interface, host string) string {

pkg/util/time_cache.go

@@ -0,0 +1,75 @@
+/*
+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 util
+
+import (
+	"sync"
+	"time"
+)
+
+// T stands in for any type in TimeCache
+// Should make it easy to use this as a template for an autogenerator
+// if we ever start doing that.
+type T interface{}
+
+type TimeCache interface {
+	// Get will fetch an item from the cache if
+	// it is present and recent enough.
+	Get(key string) T
+}
+
+type timeCacheEntry struct {
+	item       T
+	lastUpdate time.Time
+}
+
+type timeCache struct {
+	clock    Clock
+	fillFunc func(string) T
+	cache    map[string]timeCacheEntry
+	lock     sync.Mutex
+	ttl      time.Duration
+}
+
+// NewTimeCache returns a cache which calls fill to fill its entries, and
+// forgets entries after ttl has passed.
+func NewTimeCache(clock Clock, ttl time.Duration, fill func(key string) T) TimeCache {
+	return &timeCache{
+		clock:    clock,
+		fillFunc: fill,
+		cache:    map[string]timeCacheEntry{},
+		ttl:      ttl,
+	}
+}
+
+// Get returns the value of key from the cache, if it is present
+// and recent enough; otherwise, it blocks while it gets the value.
+func (c *timeCache) Get(key string) T {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	data, ok := c.cache[key]
+	now := c.clock.Now()
+
+	if !ok || now.Sub(data.lastUpdate) > c.ttl {
+		data = timeCacheEntry{
+			item:       c.fillFunc(key),
+			lastUpdate: now,
+		}
+		c.cache[key] = data
+	}
+	return data.item
+}

pkg/util/time_cache_test.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2015 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 util
+
+import (
+	"testing"
+	"time"
+)
+
+func TestCacheExpire(t *testing.T) {
+	calls := map[string]int{}
+	ff := func(key string) T { calls[key]++; return key }
+	clock := &FakeClock{time.Now()}
+
+	c := NewTimeCache(clock, 60*time.Second, ff)
+
+	c.Get("foo")
+	c.Get("bar")
+	// This call should hit the cache, so we expect no additional calls
+	c.Get("foo")
+	// Advance the clock, this call should miss the cache, so expect one more call.
+	clock.Time = clock.Time.Add(61 * time.Second)
+	c.Get("foo")
+	c.Get("bar")
+
+	if e, a := 2, calls["foo"]; e != a {
+		t.Errorf("Wrong number of calls for foo: wanted %v, got %v", e, a)
+	}
+	if e, a := 2, calls["bar"]; e != a {
+		t.Errorf("Wrong number of calls for bar: wanted %v, got %v", e, a)
+	}
+}
+
+func TestCacheNotExpire(t *testing.T) {
+	calls := map[string]int{}
+	ff := func(key string) T { calls[key]++; return key }
+	clock := &FakeClock{time.Now()}
+
+	c := NewTimeCache(clock, 60*time.Second, ff)
+
+	c.Get("foo")
+	// This call should hit the cache, so we expect no additional calls to the cloud
+	clock.Time = clock.Time.Add(60 * time.Second)
+	c.Get("foo")
+
+	if e, a := 1, calls["foo"]; e != a {
+		t.Errorf("Wrong number of calls for foo: wanted %v, got %v", e, a)
+	}
+}