From 066e70fac24cd4233de0e45c8f2b145457ecbfc0 Mon Sep 17 00:00:00 2001
From: CJ Cullen <cjcullen@google.com>
Date: Sat, 14 May 2016 16:38:19 -0700
Subject: [PATCH] Add an LRU Expire Cache.

---
 pkg/util/cache/lruexpirecache.go      | 66 +++++++++++++++++++++++++++
 pkg/util/cache/lruexpirecache_test.go | 63 +++++++++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 pkg/util/cache/lruexpirecache.go
 create mode 100644 pkg/util/cache/lruexpirecache_test.go

diff --git a/pkg/util/cache/lruexpirecache.go b/pkg/util/cache/lruexpirecache.go
new file mode 100644
index 00000000000..22f7f27679c
--- /dev/null
+++ b/pkg/util/cache/lruexpirecache.go
@@ -0,0 +1,66 @@
+/*
+Copyright 2016 The Kubernetes Authors 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 cache
+
+import (
+	"sync"
+	"time"
+
+	"github.com/golang/groupcache/lru"
+)
+
+type LRUExpireCache struct {
+	cache *lru.Cache
+	lock  sync.RWMutex
+}
+
+func NewLRUExpireCache(maxSize int) *LRUExpireCache {
+	return &LRUExpireCache{cache: lru.New(maxSize)}
+}
+
+type cacheEntry struct {
+	value      interface{}
+	expireTime time.Time
+}
+
+func (c *LRUExpireCache) Add(key lru.Key, value interface{}, ttl time.Duration) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cache.Add(key, &cacheEntry{value, time.Now().Add(ttl)})
+	// Remove entry from cache after ttl.
+	time.AfterFunc(ttl, func() { c.remove(key) })
+}
+
+func (c *LRUExpireCache) Get(key lru.Key) (interface{}, bool) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	e, ok := c.cache.Get(key)
+	if !ok {
+		return nil, false
+	}
+	if time.Now().After(e.(*cacheEntry).expireTime) {
+		go c.remove(key)
+		return nil, false
+	}
+	return e.(*cacheEntry).value, true
+}
+
+func (c *LRUExpireCache) remove(key lru.Key) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cache.Remove(key)
+}
diff --git a/pkg/util/cache/lruexpirecache_test.go b/pkg/util/cache/lruexpirecache_test.go
new file mode 100644
index 00000000000..07465ea5643
--- /dev/null
+++ b/pkg/util/cache/lruexpirecache_test.go
@@ -0,0 +1,63 @@
+/*
+Copyright 2016 The Kubernetes Authors 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 cache
+
+import (
+	"testing"
+	"time"
+
+	"github.com/golang/groupcache/lru"
+)
+
+func expectEntry(t *testing.T, c *LRUExpireCache, key lru.Key, value interface{}) {
+	result, ok := c.Get(key)
+	if !ok || result != value {
+		t.Errorf("Expected cache[%v]: %v, got %v", key, value, result)
+	}
+}
+
+func expectNotEntry(t *testing.T, c *LRUExpireCache, key lru.Key) {
+	if result, ok := c.Get(key); ok {
+		t.Errorf("Expected cache[%v] to be empty, got %v", key, result)
+	}
+}
+
+func TestSimpleGet(t *testing.T) {
+	c := NewLRUExpireCache(10)
+	c.Add("long-lived", "12345", 10*time.Hour)
+	expectEntry(t, c, "long-lived", "12345")
+}
+
+func TestExpiredGet(t *testing.T) {
+	c := NewLRUExpireCache(10)
+	c.Add("short-lived", "12345", 0*time.Second)
+	expectNotEntry(t, c, "short-lived")
+}
+
+func TestLRUOverflow(t *testing.T) {
+	c := NewLRUExpireCache(4)
+	c.Add("elem1", "1", 10*time.Hour)
+	c.Add("elem2", "2", 10*time.Hour)
+	c.Add("elem3", "3", 10*time.Hour)
+	c.Add("elem4", "4", 10*time.Hour)
+	c.Add("elem5", "5", 10*time.Hour)
+	expectNotEntry(t, c, "elem1")
+	expectEntry(t, c, "elem2", "2")
+	expectEntry(t, c, "elem3", "3")
+	expectEntry(t, c, "elem4", "4")
+	expectEntry(t, c, "elem5", "5")
+}