server/config: Generic caching backend.

server/config/caching/config_test.go

Index: server/config/caching/config_test.go
diff --git a/server/config/caching/config_test.go b/server/config/caching/config_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..6a95d42fc2e8de987adb1d82f72ec76d644d7ade
--- /dev/null
+++ b/server/config/caching/config_test.go
@@ -0,0 +1,408 @@
+// Copyright 2015 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 caching
+
+import (
+	"encoding/hex"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/luci/luci-go/common/config/impl/memory"
+	"github.com/luci/luci-go/server/config"
+	"github.com/luci/luci-go/server/config/testconfig"
+
+	"golang.org/x/net/context"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+type testCache struct {
+	data     map[string][]byte
+	callback func(hit bool)
+}
+
+func (tc *testCache) Store(c context.Context, key string, expire time.Duration, value []byte) {
+	if tc.data == nil {
+		tc.data = map[string][]byte{}
+	}
+	tc.data[key] = value
+}
+
+func (tc *testCache) Retrieve(c context.Context, key string) []byte {
+	d, ok := tc.data[key]
+	if tc.callback != nil {
+		tc.callback(ok)
+	}
+	return d
+}
+
+func (tc *testCache) invalidate() {
+	tc.data = nil
+}
+
+func (tc *testCache) nothingCached() bool {
+	return len(tc.data) == 0
+}
+
+type testingBackend struct {
+	config.Backend
+
+	getContentCalls   int
+	getNoContentCalls int
+
+	err error
+}
+
+func (b *testingBackend) Get(c context.Context, configSet, path string, p config.Params) (*config.Item, error) {
+	if p.Content {
+		b.getContentCalls++
+	} else {
+		b.getNoContentCalls++
+	}
+
+	if b.err != nil {
+		return nil, b.err
+	}
+	return b.Backend.Get(c, configSet, path, p)
+}
+
+func (b *testingBackend) GetAll(c context.Context, t config.GetAllType, path string, p config.Params) ([]*config.Item, error) {
+	if p.Content {
+		b.getContentCalls++
+	} else {
+		b.getNoContentCalls++
+	}
+
+	if b.err != nil {
+		return nil, b.err
+	}
+	return b.Backend.GetAll(c, t, path, p)
+}
+
+func (b *testingBackend) ConfigSetURL(c context.Context, a config.Authority, configSet string) (url.URL, error) {
+	b.getContentCalls++
+
+	if b.err != nil {
+		return url.URL{}, b.err
+	}
+	return b.Backend.ConfigSetURL(c, a, configSet)
+}
+
+func (b *testingBackend) reset() {
+	b.getContentCalls = 0
+	b.getNoContentCalls = 0
+}
+
+func TestConfig(t *testing.T) {
+	t.Parallel()
+
+	Convey(`A cache backed by a memory Config`, t, func() {
+		c := context.Background()
+
+		// Very simple cache.
+		var cache map[string][]byte
+		flushCache := func() {
+			cache = make(map[string][]byte)
+		}
+		flushCache()
+
+		mbase := map[string]memory.ConfigSet{
+			"services/foo": {
+				"file": "body",
+			},
+			"projects/proj1": {
+				"file": "project1 file",
+			},
+			"projects/goesaway": {
+				"file": "goesaway file",
+			},
+			"projects/goesaway/refs/heads/master": {
+				"file": "goesaway master ref",
+			},
+			"projects/goesaway/refs/heads/other": {
+				"file": "goesaway other ref",
+			},
+		}
+		mconfig := memory.New(mbase)
+
+		// Install our backend: memory backed by cache backed by force error.
+		//
+		// Cache => Testing => In-Memory
+		var backend config.Backend
+		backend = &config.ClientBackend{
+			Provider: &testconfig.LocalClientProvider{
+				Base: mconfig,
+			},
+		}
+		tb := testingBackend{Backend: backend}
+		backend = &tb
+
+		metaFor := func(configSet, path string) *config.Meta {
+			cfg, err := mconfig.GetConfig(c, configSet, path, false)
+			if err != nil {
+				panic(err)
+			}
+			return &config.Meta{
+				ConfigSet:   cfg.ConfigSet,
+				Path:        cfg.Path,
+				ContentHash: cfg.ContentHash,
+				Revision:    cfg.Revision,
+			}
+		}
+
+		var expired bool
+		backend = &Backend{
+			Backend: backend,
+			CacheGet: func(c context.Context, k Key, l Loader) (*Value, error) {
+				cacheKey := hex.EncodeToString(k.ParamHash())
+
+				var v *Value
+				if d, ok := cache[cacheKey]; ok {
+					dv, err := DecodeValue(d)
+					if err != nil {
+						return nil, err
+					}
+					if !expired {
+						return dv, nil
+					}
+
+					v = dv
+				}
+
+				v, err := l(c, k, v)
+				if err != nil {
+					return nil, err
+				}
+				d, err := v.Encode()
+				if err != nil {
+					panic(err)
+				}
+				cache[cacheKey] = d
+				return v, nil
+			},
+		}
+
+		c = config.WithBackend(c, backend)
+
+		// Advance underlying config, expectation.
+		advance := func() {
+			mbase["services/foo"]["file"] = "body2"
+			mbase["services/foo"]["late"] = "late config"
+			mbase["projects/showsup"] = memory.ConfigSet{
+				"file": "shows up",
+			}
+			delete(mbase, "projects/goesaway")
+			delete(mbase, "projects/goesaway/refs/heads/master")
+			delete(mbase, "projects/goesaway/refs/heads/other")
+		}
+
+		Convey(`Get`, func() {
+			Convey(`Get works, caches, invalidates.`, func() {
+				var s string
+				So(config.Get(c, config.AsService, "services/foo", "file", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1)
+				So(s, ShouldEqual, "body")
+
+				// The value should now be cached.
+				s = ""
+				So(config.Get(c, config.AsService, "services/foo", "file", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+				So(s, ShouldEqual, "body")
+
+				// Expire content. Should do one Get w/out content, see no change, and
+				// be done.
+				expired = true
+				So(config.Get(c, config.AsService, "services/foo", "file", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 1)
+				So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+				So(s, ShouldEqual, "body")
+
+				// Backing config changes, but not expired.
+				advance()
+				expired = false
+
+				So(config.Get(c, config.AsService, "services/foo", "file", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 1) // (Unchanged)
+				So(tb.getContentCalls, ShouldEqual, 1)   // (Unchanged)
+				So(s, ShouldEqual, "body")               // Real one is "body2", but we load from cache.
+
+				// Expire local config, does full reload on hash difference.
+				expired = true
+				So(config.Get(c, config.AsService, "services/foo", "file", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 2)
+				So(tb.getContentCalls, ShouldEqual, 2)
+				So(s, ShouldEqual, "body2")
+			})
+
+			Convey(`Get w/ missing entry caches the miss.`, func() {
+				// Get missing entry.
+				var s string
+				So(config.Get(c, config.AsService, "services/foo", "late", config.String(&s), nil), ShouldEqual, config.ErrNoConfig)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1)
+
+				// Entry is still gone (cached).
+				So(config.Get(c, config.AsService, "services/foo", "late", config.String(&s), nil), ShouldEqual, config.ErrNoConfig)
+				So(tb.getNoContentCalls, ShouldEqual, 0) // (Unchanged)
+				So(tb.getContentCalls, ShouldEqual, 1)   // (Unchanged)
+
+				// Entry comes into existence, but still cached as gone.
+				advance()
+
+				So(config.Get(c, config.AsService, "services/foo", "late", config.String(&s), nil), ShouldEqual, config.ErrNoConfig)
+				So(tb.getNoContentCalls, ShouldEqual, 0) // (Unchanged)
+				So(tb.getContentCalls, ShouldEqual, 1)   // (Unchanged)
+
+				// Cache expires, entry content is loaded.
+				expired = true
+				So(config.Get(c, config.AsService, "services/foo", "late", config.String(&s), nil), ShouldBeNil)
+				So(tb.getNoContentCalls, ShouldEqual, 0) // (Unchanged)
+				So(tb.getContentCalls, ShouldEqual, 2)
+				So(s, ShouldEqual, "late config")
+
+				// Entry disappears, re-caches as missing through no content load.
+				expired = true
+				delete(mbase["services/foo"], "late")
+
+				So(config.Get(c, config.AsService, "services/foo", "late", config.String(&s), nil), ShouldEqual, config.ErrNoConfig)
+				So(tb.getNoContentCalls, ShouldEqual, 1)
+				So(tb.getContentCalls, ShouldEqual, 2) // (Unchanged)
+			})
+		})
+
+		Convey(`GetAll`, func() {
+			Convey(`Successfully loads, caches, refreshes projects.`, func() {
+				origMetas := []*config.Meta{
+					metaFor("projects/goesaway", "file"),
+					metaFor("projects/proj1", "file"),
+				}
+
+				// Load all successfully.
+				var s []string
+				var meta []*config.Meta
+				So(config.GetAll(c, config.AsService, config.Project, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"goesaway file", "project1 file"})
+				So(meta, ShouldResemble, origMetas)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1)
+
+				// Expire the cache, reloads, same entries, no content only.
+				expired = true
+				So(config.GetAll(c, config.AsService, config.Project, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"goesaway file", "project1 file"})
+				So(meta, ShouldResemble, origMetas)
+				So(tb.getNoContentCalls, ShouldEqual, 1)
+				So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+
+				// Advance, "projects/goesaway" goes away, still loads all successfully
+				// (cache).
+				expired = false
+				advance()
+
+				So(config.GetAll(c, config.AsService, config.Project, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"goesaway file", "project1 file"})
+				So(meta, ShouldResemble, origMetas)
+				So(tb.getNoContentCalls, ShouldEqual, 1) // (Unchanged)
+				So(tb.getContentCalls, ShouldEqual, 1)   // (Unchanged)
+
+				// Expire the cache, reloads, notices missing entry (count same), reloads.
+				expired = true
+
+				So(config.GetAll(c, config.AsService, config.Project, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"project1 file", "shows up"})
+				So(meta, ShouldResemble, []*config.Meta{
+					metaFor("projects/proj1", "file"),
+					metaFor("projects/showsup", "file"),
+				})
+				So(tb.getNoContentCalls, ShouldEqual, 2)
+				So(tb.getContentCalls, ShouldEqual, 2)
+
+				// Expire the cache, reloads, notices missing entry (count differs),
+				// reloads.
+				delete(mbase, "projects/showsup")
+				expired = true
+
+				So(config.GetAll(c, config.AsService, config.Project, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"project1 file"})
+				So(meta, ShouldResemble, []*config.Meta{
+					metaFor("projects/proj1", "file"),
+				})
+				So(tb.getNoContentCalls, ShouldEqual, 3)
+				So(tb.getContentCalls, ShouldEqual, 3)
+			})
+
+			Convey(`Works with refs too.`, func() {
+				origMetas := []*config.Meta{
+					metaFor("projects/goesaway/refs/heads/master", "file"),
+					metaFor("projects/goesaway/refs/heads/other", "file"),
+				}
+
+				// Load all successfully.
+				var s []string
+				var meta []*config.Meta
+
+				So(config.GetAll(c, config.AsService, config.Ref, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"goesaway master ref", "goesaway other ref"})
+				So(meta, ShouldResemble, origMetas)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+
+				// Delete project, entries still cached.
+				advance()
+
+				So(config.GetAll(c, config.AsService, config.Ref, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string{"goesaway master ref", "goesaway other ref"})
+				So(meta, ShouldResemble, origMetas)
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+
+				// Expire the cache, reloads, same entries, no content only.
+				expired = true
+				So(config.GetAll(c, config.AsService, config.Ref, "file", config.StringSlice(&s), &meta), ShouldBeNil)
+				So(s, ShouldResemble, []string(nil))
+				So(tb.getNoContentCalls, ShouldEqual, 1)
+				So(tb.getContentCalls, ShouldEqual, 2) // (Unchanged)
+			})
+
+			Convey(`Handles no entries.`, func() {
+				var s []string
+				So(config.GetAll(c, config.AsService, config.Ref, "none", config.StringSlice(&s), nil), ShouldBeNil)
+				So(s, ShouldResemble, []string(nil))
+				So(tb.getNoContentCalls, ShouldEqual, 0)
+				So(tb.getContentCalls, ShouldEqual, 1)
+			})
+		})
+
+		Convey(`GetConfigSetURL`, func() {
+			u, err := config.GetConfigSetURL(c, config.AsService, "projects/goesaway")
+			So(err, ShouldBeNil)
+			So(u, ShouldResemble, url.URL{Scheme: "https", Host: "example.com", Path: "/fake-config/projects/goesaway"})
+			So(tb.getContentCalls, ShouldEqual, 1)
+
+			// Delete project, entries still cached.
+			advance()
+
+			u, err = config.GetConfigSetURL(c, config.AsService, "projects/goesaway")
+			So(err, ShouldBeNil)
+			So(u, ShouldResemble, url.URL{Scheme: "https", Host: "example.com", Path: "/fake-config/projects/goesaway"})
+			So(tb.getContentCalls, ShouldEqual, 1) // (Unchanged)
+
+			// Expire the cache, ErrNoConfig.
+			expired = true
+			_, err = config.GetConfigSetURL(c, config.AsService, "projects/goesaway")
+			So(err, ShouldEqual, config.ErrNoConfig)
+			So(tb.getContentCalls, ShouldEqual, 2) // Reload on expire.
+
+			// Retains "missing" cache entry.
+			expired = false
+			_, err = config.GetConfigSetURL(c, config.AsService, "projects/goesaway")
+			So(err, ShouldEqual, config.ErrNoConfig)
+			So(tb.getContentCalls, ShouldEqual, 2) // (Unchanged)
+		})
+	})
+}