Adding lru

pkg/storage/drivers/memory/lru/lru.go

@@ -0,0 +1,150 @@
+/*
+Copyright 2013 Google Inc.
+
+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.
+---
+Modifications from Minio under the following license:
+
+Minimalist Object Storage, (C) 2015 Minio, Inc.
+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 lru implements an LRU cache.
+package lru
+
+import (
+	"container/list"
+)
+
+// Cache is an LRU cache. It is not safe for concurrent access.
+type Cache struct {
+	// MaxEntries is the maximum number of cache entries before
+	// an item is evicted. Zero means no limit.
+	MaxEntries int
+
+	// OnEvicted optionally specificies a callback function to be
+	// executed when an entry is purged from the cache.
+	OnEvicted func(key Key, value interface{})
+
+	ll    *list.List
+	cache map[interface{}]*list.Element
+}
+
+// A Key may be any value that is comparable. See http://golang.org/ref/spec#Comparison_operators
+type Key interface{}
+
+type entry struct {
+	key   Key
+	value interface{}
+}
+
+// New creates a new Cache.
+// If maxEntries is zero, the cache has no limit and it's assumed
+// that eviction is done by the caller.
+func New(maxEntries int) *Cache {
+	return &Cache{
+		MaxEntries: maxEntries,
+		ll:         list.New(),
+		cache:      make(map[interface{}]*list.Element),
+	}
+}
+
+// Add adds a value to the cache.
+func (c *Cache) Add(key Key, value interface{}) {
+	if c.cache == nil {
+		c.cache = make(map[interface{}]*list.Element)
+		c.ll = list.New()
+	}
+	if ee, ok := c.cache[key]; ok {
+		c.ll.MoveToFront(ee)
+		ee.Value.(*entry).value = value
+		return
+	}
+	ele := c.ll.PushFront(&entry{key, value})
+	c.cache[key] = ele
+	if c.MaxEntries != 0 && c.ll.Len() > c.MaxEntries {
+		c.RemoveOldest()
+	}
+}
+
+// Get looks up a key's value from the cache.
+func (c *Cache) Get(key Key) (value interface{}, ok bool) {
+	if c.cache == nil {
+		return
+	}
+	if ele, hit := c.cache[key]; hit {
+		c.ll.MoveToFront(ele)
+		return ele.Value.(*entry).value, true
+	}
+	return
+}
+
+// Remove removes the provided key from the cache.
+func (c *Cache) Remove(key Key) {
+	if c.cache == nil {
+		return
+	}
+	if ele, hit := c.cache[key]; hit {
+		c.removeElement(ele)
+	}
+}
+
+// RemoveOldest removes the oldest item from the cache.
+func (c *Cache) RemoveOldest() {
+	if c.cache == nil {
+		return
+	}
+	ele := c.ll.Back()
+	if ele != nil {
+		c.removeElement(ele)
+	}
+}
+
+// GetOldest returns the oldest key, value, ok without modifying the lru
+func (c *Cache) GetOldest() (key Key, value interface{}, ok bool) {
+	if c.cache == nil {
+		return nil, nil, false
+	}
+	ele := c.ll.Back()
+	if ele != nil {
+		return ele.Value.(*entry).key, ele.Value.(*entry).value, true
+	}
+	return nil, nil, false
+}
+
+func (c *Cache) removeElement(e *list.Element) {
+	c.ll.Remove(e)
+	kv := e.Value.(*entry)
+	delete(c.cache, kv.key)
+	if c.OnEvicted != nil {
+		c.OnEvicted(kv.key, kv.value)
+	}
+}
+
+// Len returns the number of items in the cache.
+func (c *Cache) Len() int {
+	if c.cache == nil {
+		return 0
+	}
+	return c.ll.Len()
+}

pkg/storage/drivers/memory/lru/lru_test.go

@@ -0,0 +1,110 @@
+/*
+Copyright 2013 Google Inc.
+
+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.
+---
+Modifications from Minio under the following license:
+
+Minimalist Object Storage, (C) 2015 Minio, Inc.
+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 lru
+
+import (
+	"testing"
+)
+
+type simpleStruct struct {
+	int
+	string
+}
+
+type complexStruct struct {
+	int
+	simpleStruct
+}
+
+var getTests = []struct {
+	name       string
+	keyToAdd   interface{}
+	keyToGet   interface{}
+	expectedOk bool
+}{
+	{"string_hit", "myKey", "myKey", true},
+	{"string_miss", "myKey", "nonsense", false},
+	{"simple_struct_hit", simpleStruct{1, "two"}, simpleStruct{1, "two"}, true},
+	{"simeple_struct_miss", simpleStruct{1, "two"}, simpleStruct{0, "noway"}, false},
+	{"complex_struct_hit", complexStruct{1, simpleStruct{2, "three"}},
+		complexStruct{1, simpleStruct{2, "three"}}, true},
+}
+
+func TestGet(t *testing.T) {
+	for _, tt := range getTests {
+		lru := New(0)
+		lru.Add(tt.keyToAdd, 1234)
+		val, ok := lru.Get(tt.keyToGet)
+		if ok != tt.expectedOk {
+			t.Fatalf("%s: cache hit = %v; want %v", tt.name, ok, !ok)
+		} else if ok && val != 1234 {
+			t.Fatalf("%s expected get to return 1234 but got %v", tt.name, val)
+		}
+	}
+}
+
+func TestRemove(t *testing.T) {
+	lru := New(0)
+	lru.Add("myKey", 1234)
+	if val, ok := lru.Get("myKey"); !ok {
+		t.Fatal("TestRemove returned no match")
+	} else if val != 1234 {
+		t.Fatalf("TestRemove failed.  Expected %d, got %v", 1234, val)
+	}
+
+	lru.Remove("myKey")
+	if _, ok := lru.Get("myKey"); ok {
+		t.Fatal("TestRemove returned a removed entry")
+	}
+}
+
+func TestOldest(t *testing.T) {
+	lru := New(0)
+	lru.Add("a", 1)
+	lru.Add("b", 2)
+	lru.Add("c", 3)
+	key, val, ok := lru.GetOldest()
+	if ok != true {
+		t.Fatalf("%s expected get to return 1 but got %v", "a", val)
+	}
+	if key != "a" && val != 1 {
+		t.Fatalf("%s expected get to return 1 but got %v", "a", val)
+	}
+	lru.RemoveOldest()
+	key, val, ok = lru.GetOldest()
+	if ok != true {
+		t.Fatalf("%s expected get to return 1 but got %v", "a", val)
+	}
+	if key != "b" && val != 2 {
+		t.Fatalf("%s expected get to return 1 but got %v", "a", val)
+	}
+}

pkg/storage/drivers/memory/memory.go

@@ -33,9 +33,9 @@ import (
 
 	"io/ioutil"
 
-	"github.com/golang/groupcache/lru"
 	"github.com/minio-io/minio/pkg/iodine"
 	"github.com/minio-io/minio/pkg/storage/drivers"
+	"github.com/minio-io/minio/pkg/storage/drivers/memory/lru"
 	"github.com/minio-io/minio/pkg/utils/log"
 	"github.com/minio-io/minio/pkg/utils/split"
 )
@@ -59,7 +59,8 @@ type storedBucket struct {
 }
 
 type storedObject struct {
-	metadata drivers.ObjectMetadata
+	metadata     drivers.ObjectMetadata
+	lastAccessed time.Time
 }
 
 const (
@@ -483,29 +484,20 @@ func (memory *memoryDriver) expireObjects() {
 		if memory.shutdown {
 			return
 		}
-		var keysToRemove []string
 		if len(memory.objectMetadata) > 0 {
-			memory.lock.RLock()
-			var earliest time.Time
-			for key, object := range memory.objectMetadata {
-				if time.Now().Add(-memory.expiration).After(object.metadata.Created) {
-					keysToRemove = append(keysToRemove, key)
+			var sleepDuration time.Duration
+			memory.lock.Lock()
+			if k, _, ok := memory.objects.GetOldest(); ok {
+				key := k.(string)
+				object := memory.objectMetadata[key]
+				if time.Now().Sub(object.lastAccessed) > memory.expiration {
+					memory.objects.RemoveOldest()
 				} else {
-					if object.metadata.Created.Before(earliest) {
-						earliest = object.metadata.Created
-					}
+					sleepDuration = memory.expiration - time.Now().Sub(object.lastAccessed)
 				}
 			}
-			memory.lock.RUnlock()
-			memory.lock.Lock()
-			for _, key := range keysToRemove {
-				memory.objects.Remove(key)
-			}
 			memory.lock.Unlock()
-			sleepFor := earliest.Sub(time.Now())
-			if sleepFor > 0 {
-				time.Sleep(sleepFor)
-			}
+			time.Sleep(sleepDuration)
 		} else {
 			time.Sleep(memory.expiration)
 		}