blob: e68d9bc09249e9c634e7cb29763c304bcef15d2a [file] [log] [blame]
// +build appengine
// Package memcache provides an implementation of httpcache.Cache that uses App
// Engine's memcache package to store cached responses.
// When not built for Google App Engine, this package will provide an
// implementation that connects to a specified memcached server. See the
// memcache.go file in this package for details.
package memcache
import (
// Cache is an implementation of httpcache.Cache that caches responses in App
// Engine's memcache.
type Cache struct {
// cacheKey modifies an httpcache key for use in memcache. Specifically, it
// prefixes keys to avoid collision with other data stored in memcache.
func cacheKey(key string) string {
return "httpcache:" + key
// Get returns the response corresponding to key if present.
func (c *Cache) Get(key string) (resp []byte, ok bool) {
item, err := memcache.Get(c.Context, cacheKey(key))
if err != nil {
if err != memcache.ErrCacheMiss {
c.Context.Errorf("error getting cached response: %v", err)
return nil, false
return item.Value, true
// Set saves a response to the cache as key.
func (c *Cache) Set(key string, resp []byte) {
item := &memcache.Item{
Key: cacheKey(key),
Value: resp,
if err := memcache.Set(c.Context, item); err != nil {
c.Context.Errorf("error caching response: %v", err)
// Delete removes the response with key from the cache.
func (c *Cache) Delete(key string) {
if err := memcache.Delete(c.Context, cacheKey(key)); err != nil {
c.Context.Errorf("error deleting cached response: %v", err)
// New returns a new Cache for the given context.
func New(ctx appengine.Context) *Cache {
return &Cache{ctx}