server/auth: Add in-process LRU-based cache.

appengine/gaeauth/server/cache.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package server
 
 import (
         "time"
 
         "golang.org/x/net/context"
 
         "github.com/luci/gae/service/info"
         mc "github.com/luci/gae/service/memcache"
 
         "github.com/luci/luci-go/common/errors"
         "github.com/luci/luci-go/server/auth"
 )
 
-// Memcache implements auth.GlobalCache on top of GAE memcache.
+// Memcache implements auth.Cache on top of GAE memcache.
 type Memcache struct {
         Namespace string
 }
 
-var _ auth.GlobalCache = (*Memcache)(nil)
+var _ auth.Cache = (*Memcache)(nil)
 
 // Get returns a cached item or (nil, nil) if it's not in the cache.
 //
 // Any returned error is transient error.
 func (m *Memcache) Get(c context.Context, key string) ([]byte, error) {
         c = m.cacheContext(c)
 
         switch itm, err := mc.GetKey(c, key); {
         case err == mc.ErrCacheMiss:
                 return nil, nil
@@ skipping 16 matching lines @@
         if err := mc.Set(c, item); err != nil {
                 return errors.WrapTransient(err)
         }
         return nil
 }
 
 // cache returns properly namespaced memcache.Interface.
 func (m *Memcache) cacheContext(c context.Context) context.Context {
         return info.MustNamespace(c, m.Namespace)
 }