Convert 'Testable' interface into an optional filter.

go/src/infra/gae/libs/gae/filters/featureBreaker/mc.go

Index: go/src/infra/gae/libs/gae/filters/featureBreaker/mc.go
diff --git a/go/src/infra/gae/libs/gae/filters/featureBreaker/mc.go b/go/src/infra/gae/libs/gae/filters/featureBreaker/mc.go
new file mode 100644
index 0000000000000000000000000000000000000000..87289aa211ac02904953d6a7ec4f1829f767c378
--- /dev/null
+++ b/go/src/infra/gae/libs/gae/filters/featureBreaker/mc.go
@@ -0,0 +1,101 @@
+// 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 featureBreaker
+
+import (
+	"golang.org/x/net/context"
+
+	"infra/gae/libs/gae"
+)
+
+type mcState struct {
+	*state
+
+	gae.Memcache
+}
+
+func (m *mcState) Get(key string) (ret gae.MCItem, err error) {
+	err = m.run(func() (err error) {
+		ret, err = m.Memcache.Get(key)
+		return
+	})
+	return
+}
+
+func (m *mcState) GetMulti(keys []string) (ret map[string]gae.MCItem, err error) {
+	err = m.run(func() (err error) {
+		ret, err = m.Memcache.GetMulti(keys)
+		return
+	})
+	return
+}
+
+func (m *mcState) Add(item gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.Add(item) })
+}
+
+func (m *mcState) Set(item gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.Set(item) })
+}
+
+func (m *mcState) Delete(key string) error {
+	return m.run(func() error { return m.Memcache.Delete(key) })
+}
+
+func (m *mcState) CompareAndSwap(item gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.CompareAndSwap(item) })
+}
+
+func (m *mcState) AddMulti(items []gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.AddMulti(items) })
+}
+
+func (m *mcState) SetMulti(items []gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.SetMulti(items) })
+}
+
+func (m *mcState) DeleteMulti(keys []string) error {
+	return m.run(func() error { return m.Memcache.DeleteMulti(keys) })
+}
+
+func (m *mcState) Flush() error {
+	return m.run(func() error { return m.Memcache.Flush() })
+}
+
+func (m *mcState) CompareAndSwapMulti(items []gae.MCItem) error {
+	return m.run(func() error { return m.Memcache.CompareAndSwapMulti(items) })
+}
+
+func (m *mcState) Increment(key string, delta int64, initialValue uint64) (newValue uint64, err error) {
+	err = m.run(func() (err error) {
+		newValue, err = m.Memcache.Increment(key, delta, initialValue)
+		return
+	})
+	return
+}
+
+func (m *mcState) IncrementExisting(key string, delta int64) (newValue uint64, err error) {
+	err = m.run(func() (err error) {
+		newValue, err = m.Memcache.IncrementExisting(key, delta)
+		return
+	})
+	return
+}
+
+func (m *mcState) Stats() (ret *gae.MCStatistics, err error) {
+	err = m.run(func() (err error) {
+		ret, err = m.Memcache.Stats()
+		return
+	})
+	return
+}
+
+// FilterMC installs a counter Memcache filter in the context.
+func FilterMC(c context.Context, defaultError error) (context.Context, FeatureBreaker) {
+	state := newState(defaultError)
+	return gae.AddMCFilters(c, func(ic context.Context, rds gae.Memcache) gae.Memcache {
+		return &mcState{state, rds}
+	}), state
+}