Add server/cache support to gaeconfig.

luci_config/appengine/backend/memcache/cache_test.go

Index: luci_config/appengine/backend/memcache/cache_test.go
diff --git a/luci_config/appengine/backend/memcache/cache_test.go b/luci_config/appengine/backend/memcache/cache_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..9ba85107adbb51d0142194c995d5bfddb2dc42a7
--- /dev/null
+++ b/luci_config/appengine/backend/memcache/cache_test.go
@@ -0,0 +1,137 @@
+// 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 memcache
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/luci/luci-go/common/clock/testclock"
+	memconfig "github.com/luci/luci-go/common/config/impl/memory"
+	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/luci_config/server/cfgclient"
+	"github.com/luci/luci-go/luci_config/server/cfgclient/backend"
+	"github.com/luci/luci-go/luci_config/server/cfgclient/backend/caching"
+	"github.com/luci/luci-go/luci_config/server/cfgclient/backend/client"
+	"github.com/luci/luci-go/luci_config/server/cfgclient/backend/testconfig"
+
+	"github.com/luci/gae/filter/featureBreaker"
+	"github.com/luci/gae/impl/memory"
+	mc "github.com/luci/gae/service/memcache"
+
+	"golang.org/x/net/context"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestMemcache(t *testing.T) {
+	t.Parallel()
+
+	Convey("Test cache", t, func() {
+		c := context.Background()
+		c = memory.Use(c)
+
+		c, clk := testclock.UseTime(c, testclock.TestTimeUTC)
+		_ = clk
+
+		c, mcFB := featureBreaker.FilterMC(c, nil)
+
+		getMCStats := func(c context.Context) *mc.Statistics {
+			st, err := mc.Stats(c)
+			if err != nil {
+				panic(err)
+			}
+			return st
+		}
+
+		configDB := map[string]memconfig.ConfigSet{
+			"projects/foo": {
+				"test.cfg": "foo",
+			},
+		}
+
+		var be backend.B
+		be = &client.Backend{
+			Provider: &testconfig.Provider{
+				Base: memconfig.New(configDB),
+			},
+		}
+		be = Backend(be, time.Minute)
+		c = backend.WithBackend(c, be)
+
+		Convey(`Pulling items from memcache`, func() {
+			var content string
+
+			Convey(`Should be able to fetch a config as service`, func() {
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, "foo")
+				So(getMCStats(c).Misses, ShouldEqual, 1)
+				So(getMCStats(c).Hits, ShouldEqual, 0)
+				So(getMCStats(c).Items, ShouldEqual, 1)
+
+				// A second fetch hits memcache.
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, "foo")
+				So(getMCStats(c).Misses, ShouldEqual, 1)
+				So(getMCStats(c).Hits, ShouldEqual, 1)
+				So(getMCStats(c).Items, ShouldEqual, 1)
+
+				// Memcache expires, full reload.
+				clk.Add(time.Minute)
+
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, "foo")
+				So(getMCStats(c).Misses, ShouldEqual, 2)
+				So(getMCStats(c).Hits, ShouldEqual, 1)
+				So(getMCStats(c).Items, ShouldEqual, 1)
+			})
+
+			Convey(`When memcache is broken`, func() {
+				testErr := errors.New("test error")
+				mcFB.BreakFeatures(testErr, "GetMulti")
+
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, "foo")
+				So(getMCStats(c).Misses, ShouldEqual, 0)
+				So(getMCStats(c).Hits, ShouldEqual, 0)
+				So(getMCStats(c).Items, ShouldEqual, 0)
+			})
+
+			Convey(`When a cached entry is corrupted`, func() {
+				cacheKey := caching.Key{
+					Schema:    caching.Schema,
+					Op:        caching.OpGet,
+					ConfigSet: "projects/foo",
+					Path:      "test.cfg",
+					Content:   true,
+					Authority: backend.AsService,
+				}
+				So(mc.Set(c, mc.NewItem(c, memcacheKey(&cacheKey)).SetValue([]byte("!!! trash !!!"))), ShouldBeNil)
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, "foo")
+				So(getMCStats(c).Misses, ShouldEqual, 0)
+				So(getMCStats(c).Hits, ShouldEqual, 1)
+				So(getMCStats(c).Items, ShouldEqual, 1)
+			})
+
+			Convey(`Will skip the cache if an item is too large.`, func() {
+				// We need to use a pseudo-random string b/c we compress it.
+				buf := make([]byte, maxMemCacheSize*2)
+				rng := rand.New(rand.NewSource(0))
+				_, _ = rng.Read(buf)
+
+				orig := string(buf)
+				configDB["projects/foo"]["test.cfg"] = orig
+
+				So(cfgclient.Get(c, cfgclient.AsService, "projects/foo", "test.cfg", cfgclient.String(&content), nil), ShouldBeNil)
+				So(content, ShouldEqual, orig)
+				So(getMCStats(c).Misses, ShouldEqual, 1)
+				So(getMCStats(c).Hits, ShouldEqual, 0)
+				So(getMCStats(c).Items, ShouldEqual, 0)
+			})
+		})
+	})
+}