A transparent cache for datastore, backed by memcache.

filter/dscache/context.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package dscache
+
+import (
+        ds "github.com/luci/gae/service/datastore"
+        "github.com/luci/gae/service/info"
+        mc "github.com/luci/gae/service/memcache"
+        "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/common/mathrand"
+        "golang.org/x/net/context"
+)
+
+type key int
+
+var dsTxnCacheKey key
+
+// FilterRDS installs a counter RawDatastore filter in the context.
+func FilterRDS(c context.Context) context.Context {
+        return ds.AddRawFilters(c, func(ic context.Context, ds ds.RawInterface) ds.RawInterface {
+                i := info.Get(ic)
+                aid, ns := i.AppID(), i.GetNamespace()
+
+                v := ic.Value(dsTxnCacheKey)
+                if v == nil {
+                        return &dsCache{ds, aid, ns, mc.Get(ic), logging.Get(ic), mathrand.Get(ic)}
+                }
+                return &dsTxnCache{ds, v.(*dsTxnState), mc.Get(ic)}
+        })
+}