A transparent cache for datastore, backed by memcache.

filter/dscache/dscache_test.go

Index: filter/dscache/dscache_test.go
diff --git a/filter/dscache/dscache_test.go b/filter/dscache/dscache_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..b01b924ecb2fb9e8a2b5651c931a19db140a9c0d
--- /dev/null
+++ b/filter/dscache/dscache_test.go
@@ -0,0 +1,104 @@
+// 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 (
+	"fmt"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/luci/gae/impl/memory"
+	"github.com/luci/gae/service/datastore"
+	"github.com/luci/gae/service/memcache"
+	"github.com/luci/luci-go/common/clock"
+	"github.com/luci/luci-go/common/clock/testclock"
+	"github.com/luci/luci-go/common/mathrand"
+	. "github.com/smartystreets/goconvey/convey"
+	"golang.org/x/net/context"
+)
+
+type object struct {
+	ID int64 `gae:"$id"`
+
+	Value string
+}
+
+func TestDSCache(t *testing.T) {
+	t.Parallel()
+
+	zeroTime, err := time.Parse("2006-01-02T15:04:05.999999999Z", "2006-01-02T15:04:05.999999999Z")
+	if err != nil {
+		panic(err)
+	}
+
+	Convey("Test dscache", t, func() {
+		c := mathrand.Set(context.Background(), rand.New(rand.NewSource(1)))
+		clk := testclock.New(zeroTime)
+		c = clock.Set(c, clk)
+		c = memory.Use(c)
+		dsUnder := datastore.Get(c)
+		ds := datastore.Get(FilterRDS(c))
+		mc := memcache.Get(c)
+
+		itmFor := func(i int, k datastore.Key) memcache.Item {
+			return mc.NewItem(fmt.Sprintf(KeyFormat, i, mkKeySuffix(k)))
+		}
+
+		So(dsUnder, ShouldNotBeNil)
+		So(ds, ShouldNotBeNil)
+		So(mc, ShouldNotBeNil)
+
+		Convey("basically works", func() {
+			o := object{ID: 1, Value: "hi"}
+			So(ds.Put(&o), ShouldBeNil)
+
+			o = object{ID: 1}
+			So(dsUnder.Get(&o), ShouldBeNil)
+			So(o.Value, ShouldEqual, "hi")
+
+			itm := itmFor(0, ds.KeyForObj(&o))
+			So(mc.Get(itm), ShouldEqual, memcache.ErrCacheMiss)
+
+			o = object{ID: 1}
+			So(ds.Get(&o), ShouldBeNil)
+			So(o.Value, ShouldEqual, "hi")
+			So(mc.Get(itm), ShouldBeNil)
+			So(itm.Value(), ShouldResemble,
+				[]byte("\x00\x80\x80W1[\x8fW(\x80\x80\x06i5@"))
+
+			Convey("now we don't need the datastore!", func() {
+				o := object{ID: 1}
+
+				// delete it, bypassing the cache filter. Don't do this in production
+				// unless you want a crappy cache.
+				So(dsUnder.Delete(ds.KeyForObj(&o)), ShouldBeNil)
+
+				itm := itmFor(0, ds.KeyForObj(&o))
+				So(mc.Get(itm), ShouldBeNil)
+				So(itm.Value(), ShouldResemble,
+					[]byte("\x00\x80\x80W1[\x8fW(\x80\x80\x06i5@"))

[iannucci, 2015/08/04 05:26:17]

for reference, the equivalent gob encoding is 57 bytes :P

+
+				So(ds.Get(&o), ShouldBeNil)
+				So(o.Value, ShouldEqual, "hi")
+			})
+
+			Convey("deleting it properly records that", func() {
+				o := object{ID: 1}
+				So(ds.Delete(ds.KeyForObj(&o)), ShouldBeNil)
+
+				itm := itmFor(0, ds.KeyForObj(&o))
+				So(mc.Get(itm), ShouldEqual, memcache.ErrCacheMiss)
+				So(ds.Get(&o), ShouldEqual, datastore.ErrNoSuchEntity)
+
+				So(mc.Get(itm), ShouldBeNil)
+				So(itm.Value(), ShouldResemble, []byte{})
+
+				// this one hits memcache
+				So(ds.Get(&o), ShouldEqual, datastore.ErrNoSuchEntity)
+			})
+		})
+	})
+}