Merge pull request #827 from aaronlehmann/read-only-mode-2

Add a read-only mode as a configuration option

docs/configuration.md

@@ -118,6 +118,8 @@ information about each option that appears later in this page.
           age: 168h
           interval: 24h
           dryrun: false
+        readonly:
+          enabled: false
     auth:
       silly:
         realm: silly-realm
@@ -644,14 +646,15 @@ This storage backend uses Amazon's Simple Storage Service (S3).
 
 ### Maintenance
 
-Currently the registry can perform one maintenance function: upload purging.  This and future
-maintenance functions which are related to storage can be configured under the maintenance section.
+Currently upload purging and read-only mode are the only maintenance functions available.
+These and future maintenance functions which are related to storage can be configured under
+the maintenance section.
 
 ### Upload Purging
 
 Upload purging is a background process that periodically removes orphaned files from the upload
 directories of the registry.  Upload purging is enabled by default.  To
- configure upload directory purging, the following parameters
+configure upload directory purging, the following parameters
 must be set.
 
 
@@ -664,6 +667,16 @@ must be set.
 
 Note: `age` and `interval` are strings containing a number with optional fraction and a unit suffix: e.g. 45m, 2h10m, 168h (1 week).
 
+### Read-only mode
+
+If the `readonly` section under `maintenance` has `enabled` set to `true`,
+clients will not be allowed to write to the registry. This mode is useful to
+temporarily prevent writes to the backend storage so a garbage collection pass
+can be run.  Before running garbage collection, the registry should be
+restarted with readonly's `enabled` set to true. After the garbage collection
+pass finishes, the registry may be restarted again, this time with `readonly`
+removed from the configuration (or set to false).
+
 ### Openstack Swift
 
 This storage backend uses Openstack Swift object storage.

registry/handlers/api_test.go

@@ -633,6 +633,54 @@ func TestDeleteDisabled(t *testing.T) {
 	checkResponse(t, "deleting layer with delete disabled", resp, http.StatusMethodNotAllowed)
 }
 
+func TestDeleteReadOnly(t *testing.T) {
+	env := newTestEnv(t, true)
+
+	imageName := "foo/bar"
+	// "build" our layer file
+	layerFile, tarSumStr, err := testutil.CreateRandomTarFile()
+	if err != nil {
+		t.Fatalf("error creating random layer file: %v", err)
+	}
+
+	layerDigest := digest.Digest(tarSumStr)
+	layerURL, err := env.builder.BuildBlobURL(imageName, layerDigest)
+	if err != nil {
+		t.Fatalf("Error building blob URL")
+	}
+	uploadURLBase, _ := startPushLayer(t, env.builder, imageName)
+	pushLayer(t, env.builder, imageName, layerDigest, uploadURLBase, layerFile)
+
+	env.app.readOnly = true
+
+	resp, err := httpDelete(layerURL)
+	if err != nil {
+		t.Fatalf("unexpected error deleting layer: %v", err)
+	}
+
+	checkResponse(t, "deleting layer in read-only mode", resp, http.StatusMethodNotAllowed)
+}
+
+func TestStartPushReadOnly(t *testing.T) {
+	env := newTestEnv(t, true)
+	env.app.readOnly = true
+
+	imageName := "foo/bar"
+
+	layerUploadURL, err := env.builder.BuildBlobUploadURL(imageName)
+	if err != nil {
+		t.Fatalf("unexpected error building layer upload url: %v", err)
+	}
+
+	resp, err := http.Post(layerUploadURL, "", nil)
+	if err != nil {
+		t.Fatalf("unexpected error starting layer push: %v", err)
+	}
+	defer resp.Body.Close()
+
+	checkResponse(t, "starting push in read-only mode", resp, http.StatusMethodNotAllowed)
+}
+
 func httpDelete(url string) (*http.Response, error) {
 	req, err := http.NewRequest("DELETE", url, nil)
 	if err != nil {

registry/handlers/app.go

@@ -69,6 +69,9 @@ type App struct {
 
 	// true if this registry is configured as a pull through cache
 	isCache bool
+
+	// true if the registry is in a read-only maintenance mode
+	readOnly bool
 }
 
 // NewApp takes a configuration and returns a configured app, ready to serve
@@ -104,13 +107,24 @@ func NewApp(ctx context.Context, configuration *configuration.Configuration) *Ap
 
 	purgeConfig := uploadPurgeDefaultConfig()
 	if mc, ok := configuration.Storage["maintenance"]; ok {
-		for k, v := range mc {
-			switch k {
-			case "uploadpurging":
-				purgeConfig = v.(map[interface{}]interface{})
+		if v, ok := mc["uploadpurging"]; ok {
+			purgeConfig, ok = v.(map[interface{}]interface{})
+			if !ok {
+				panic("uploadpurging config key must contain additional keys")
+			}
+		}
+		if v, ok := mc["readonly"]; ok {
+			readOnly, ok := v.(map[interface{}]interface{})
+			if !ok {
+				panic("readonly config key must contain additional keys")
+			}
+			if readOnlyEnabled, ok := readOnly["enabled"]; ok {
+				app.readOnly, ok = readOnlyEnabled.(bool)
+				if !ok {
+					panic("readonly's enabled config key must have a boolean value")
+				}
 			}
 		}
-
 	}
 
 	startUploadPurger(app, app.driver, ctxu.GetLogger(app), purgeConfig)

registry/handlers/blob.go

@@ -32,11 +32,16 @@ func blobDispatcher(ctx *Context, r *http.Request) http.Handler {
 		Digest:  dgst,
 	}
 
-	return handlers.MethodHandler{
+	mhandler := handlers.MethodHandler{
 		"GET":  http.HandlerFunc(blobHandler.GetBlob),
 		"HEAD": http.HandlerFunc(blobHandler.GetBlob),
-		"DELETE": http.HandlerFunc(blobHandler.DeleteBlob),
 	}
+
+	if !ctx.readOnly {
+		mhandler["DELETE"] = http.HandlerFunc(blobHandler.DeleteBlob)
+	}
+
+	return mhandler
 }
 
 // blobHandler serves http blob requests.

registry/handlers/blobupload.go

@@ -22,14 +22,17 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 		UUID:    getUploadUUID(ctx),
 	}
 
-	handler := http.Handler(handlers.MethodHandler{
-		"POST":   http.HandlerFunc(buh.StartBlobUpload),
+	handler := handlers.MethodHandler{
 		"GET":  http.HandlerFunc(buh.GetUploadStatus),
 		"HEAD": http.HandlerFunc(buh.GetUploadStatus),
-		"PATCH":  http.HandlerFunc(buh.PatchBlobData),
-		"PUT":    http.HandlerFunc(buh.PutBlobUploadComplete),
-		"DELETE": http.HandlerFunc(buh.CancelBlobUpload),
-	})
+	}
+
+	if !ctx.readOnly {
+		handler["POST"] = http.HandlerFunc(buh.StartBlobUpload)
+		handler["PATCH"] = http.HandlerFunc(buh.PatchBlobData)
+		handler["PUT"] = http.HandlerFunc(buh.PutBlobUploadComplete)
+		handler["DELETE"] = http.HandlerFunc(buh.CancelBlobUpload)
+	}
 
 	if buh.UUID != "" {
 		state, err := hmacKey(ctx.Config.HTTP.Secret).unpackUploadState(r.FormValue("_state"))
@@ -93,7 +96,7 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 			}
 		}
 
-		handler = closeResources(handler, buh.Upload)
+		return closeResources(handler, buh.Upload)
 	}
 
 	return handler

registry/handlers/images.go

@@ -32,11 +32,16 @@ func imageManifestDispatcher(ctx *Context, r *http.Request) http.Handler {
 		imageManifestHandler.Digest = dgst
 	}
 
-	return handlers.MethodHandler{
+	mhandler := handlers.MethodHandler{
 		"GET": http.HandlerFunc(imageManifestHandler.GetImageManifest),
-		"PUT":    http.HandlerFunc(imageManifestHandler.PutImageManifest),
-		"DELETE": http.HandlerFunc(imageManifestHandler.DeleteImageManifest),
 	}
+
+	if !ctx.readOnly {
+		mhandler["PUT"] = http.HandlerFunc(imageManifestHandler.PutImageManifest)
+		mhandler["DELETE"] = http.HandlerFunc(imageManifestHandler.DeleteImageManifest)
+	}
+
+	return mhandler
 }
 
 // imageManifestHandler handles http operations on image manifests.