Allow control over which storage cache to use

This allows one to better control the usage of the cache and turn it off
completely. The storage configuration module was modified to allow parameters
to be passed to just the storage implementation, rather than to the driver.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

cmd/registry/config.yml

@@ -5,6 +5,8 @@ log:
     service: registry
     environment: development
 storage:
+    cache:
+        layerinfo: inmemory
     filesystem:
         rootdirectory: /tmp/registry-dev
 http:

configuration/configuration.go

@@ -187,8 +187,13 @@ type Storage map[string]Parameters
 func (storage Storage) Type() string {
 	// Return only key in this map
 	for k := range storage {
+		switch k {
+		case "cache":
+			// allow configuration of caching
+		default:
 			return k
 		}
+	}
 	return ""
 }
 
@@ -211,10 +216,18 @@ func (storage *Storage) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		if len(storageMap) > 1 {
 			types := make([]string, 0, len(storageMap))
 			for k := range storageMap {
+				switch k {
+				case "cache":
+					// allow configuration of caching
+				default:
 					types = append(types, k)
 				}
+			}
+
+			if len(types) > 1 {
 				return fmt.Errorf("Must provide exactly one storage type. Provided: %v", types)
 			}
+		}
 		*storage = storageMap
 		return nil
 	}

doc/configuration.md

@@ -28,6 +28,8 @@ storage:
 		v4auth: true
 		chunksize: 5242880
 		rootdirectory: /s3/object/name/prefix
+	cache:
+		layerinfo: inmemory
 auth:
 	silly:
 		realm: silly-realm
@@ -162,10 +164,20 @@ storage:
 		v4auth: true
 		chunksize: 5242880
 		rootdirectory: /s3/object/name/prefix
+	cache:
+		layerinfo: inmemory
 ```
 
 The storage option is **required** and defines which storage backend is in use. At the moment only one backend may be configured, an error is returned when the registry is started with more than one storage backend configured.
 
+A `cache` subsection can be used to enable caching of data accessed in the
+storage backend. Currently, the only available cache provides fast access to
+layer metadata. This if configured using the `layerinfo` field. The following
+cache implementations are available:
+
+- redis: using the redis pool to cache layer meta data.
+- inmemory: use an in memory map to cache layer meta data.
+
 The following backends may be configured, **all options for a given storage backend are required**:
 
 ### filesystem

registry/handlers/app.go

@@ -103,11 +103,28 @@ func NewApp(ctx context.Context, configuration configuration.Configuration) *App
 	app.configureEvents(&configuration)
 	app.configureRedis(&configuration)
 
-	if app.redis != nil {
+	// configure storage caches
+	if cc, ok := configuration.Storage["cache"]; ok {
+		switch cc["layerinfo"] {
+		case "redis":
+			if app.redis == nil {
+				panic("redis configuration required to use for layerinfo cache")
+			}
 			app.registry = storage.NewRegistryWithDriver(app.driver, cache.NewRedisLayerInfoCache(app.redis))
-	} else {
-		// always fall back to inmemory storage
+			ctxu.GetLogger(app).Infof("using redis layerinfo cache")
+		case "inmemory":
 			app.registry = storage.NewRegistryWithDriver(app.driver, cache.NewInMemoryLayerInfoCache())
+			ctxu.GetLogger(app).Infof("using inmemory layerinfo cache")
+		default:
+			if cc["layerinfo"] != "" {
+				ctxu.GetLogger(app).Warnf("unkown cache type %q, caching disabled", configuration.Storage["cache"])
+			}
+		}
+	}
+
+	if app.registry == nil {
+		// configure the registry if no cache section is available.
+		app.registry = storage.NewRegistryWithDriver(app.driver, nil)
 	}
 
 	app.registry, err = applyRegistryMiddleware(app.registry, configuration.Middleware["registry"])