Add an "enabled" parameter under "readonly", and make it as if the mutable handlers don't exist when read-only mode is enabled

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

docs/configuration.md

@@ -118,7 +118,8 @@ information about each option that appears later in this page.
           age: 168h
           interval: 24h
           dryrun: false
-        readonly: false
+        readonly:
+          enabled: false
     auth:
       silly:
         realm: silly-realm
@@ -667,12 +668,13 @@ Note: `age` and `interval` are strings containing a number with optional fractio
 
 ### Read-only mode
 
-If the `readonly` parameter in the `maintenance` section is set to true, clients
+If the `readonly` section under `maintenance` has `enabled` set to `true`,
-will not be allowed to write to the registry. This mode is useful to temporarily
+clients will not be allowed to write to the registry. This mode is useful to
-prevent writes to the backend storage so a garbage collection pass can be run.
+temporarily prevent writes to the backend storage so a garbage collection pass
-Before running garbage collection, the registry should be restarted with
+can be run.  Before running garbage collection, the registry should be
-`readonly` set to true. After the garbage collection pass finishes, the registry
+restarted with readonly's `enabled` set to true. After the garbage collection
-may be restarted again, this time with `readonly` removed from the configuration.
+pass finishes, the registry may be restarted again, this time with `readonly`
+removed from the configuration (or set to false).
 
 ### Openstack Swift
 

registry/api/v2/errors.go

@@ -133,14 +133,4 @@ var (
 		longer proceed.`,
 		HTTPStatusCode: http.StatusNotFound,
 	})
-
-	// ErrorCodeMaintenanceMode is returned when an upload can't be
-	// accepted because the registry is in maintenance mode.
-	ErrorCodeMaintenanceMode = errcode.Register(errGroup, errcode.ErrorDescriptor{
-		Value:   "MAINTENANCE_MODE",
-		Message: "registry in maintenance mode",
-		Description: `The upload cannot be accepted because the registry
-		is running read-only in maintenance mode.`,
-		HTTPStatusCode: http.StatusServiceUnavailable,
-	})
 )

registry/handlers/api_test.go

@@ -658,7 +658,7 @@ func TestDeleteReadOnly(t *testing.T) {
 		t.Fatalf("unexpected error deleting layer: %v", err)
 	}
 
-	checkResponse(t, "deleting layer in read-only mode", resp, http.StatusServiceUnavailable)
+	checkResponse(t, "deleting layer in read-only mode", resp, http.StatusMethodNotAllowed)
 }
 
 func TestStartPushReadOnly(t *testing.T) {
@@ -678,7 +678,7 @@ func TestStartPushReadOnly(t *testing.T) {
 	}
 	defer resp.Body.Close()
 
-	checkResponse(t, "starting push in read-only mode", resp, http.StatusServiceUnavailable)
+	checkResponse(t, "starting push in read-only mode", resp, http.StatusMethodNotAllowed)
 }
 
 func httpDelete(url string) (*http.Response, error) {

registry/handlers/app.go

@@ -109,9 +109,15 @@ func NewApp(ctx context.Context, configuration *configuration.Configuration) *Ap
 			}
 		}
 		if v, ok := mc["readonly"]; ok {
-			app.readOnly, ok = v.(bool)
+			readOnly, ok := v.(map[interface{}]interface{})
 			if !ok {
-				panic("readonly config key must have a boolean value")
+				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")
+				}
 			}
 		}
 	}

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),
+		"GET":  http.HandlerFunc(blobHandler.GetBlob),
-		"HEAD":   http.HandlerFunc(blobHandler.GetBlob),
+		"HEAD": http.HandlerFunc(blobHandler.GetBlob),
-		"DELETE": mutableHandler(blobHandler.DeleteBlob, ctx),
 	}
+
+	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{
+	handler := handlers.MethodHandler{
-		"POST":   mutableHandler(buh.StartBlobUpload, ctx),
+		"GET":  http.HandlerFunc(buh.GetUploadStatus),
-		"GET":    http.HandlerFunc(buh.GetUploadStatus),
+		"HEAD": http.HandlerFunc(buh.GetUploadStatus),
-		"HEAD":   http.HandlerFunc(buh.GetUploadStatus),
+	}
-		"PATCH":  mutableHandler(buh.PatchBlobData, ctx),
+
-		"PUT":    mutableHandler(buh.PutBlobUploadComplete, ctx),
+	if !ctx.readOnly {
-		"DELETE": mutableHandler(buh.CancelBlobUpload, ctx),
+		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/helpers.go

@@ -7,7 +7,6 @@ import (
 
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/registry/api/errcode"
-	"github.com/docker/distribution/registry/api/v2"
 )
 
 // closeResources closes all the provided resources after running the target
@@ -61,16 +60,3 @@ func copyFullPayload(responseWriter http.ResponseWriter, r *http.Request, destWr
 
 	return nil
 }
-
-// mutableHandler wraps a http.HandlerFunc with a check that the registry is
-// not in read-only mode. If it is in read-only mode, the wrapper returns
-// v2.ErrorCodeMaintenanceMode to the client.
-func mutableHandler(handler http.HandlerFunc, ctx *Context) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		if ctx.App.readOnly {
-			ctx.Errors = append(ctx.Errors, v2.ErrorCodeMaintenanceMode)
-			return
-		}
-		handler(w, r)
-	}
-}

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),
+		"GET": http.HandlerFunc(imageManifestHandler.GetImageManifest),
-		"PUT":    mutableHandler(imageManifestHandler.PutImageManifest, ctx),
-		"DELETE": mutableHandler(imageManifestHandler.DeleteImageManifest, ctx),
 	}
+
+	if !ctx.readOnly {
+		mhandler["PUT"] = http.HandlerFunc(imageManifestHandler.PutImageManifest)
+		mhandler["DELETE"] = http.HandlerFunc(imageManifestHandler.DeleteImageManifest)
+	}
+
+	return mhandler
 }
 
 // imageManifestHandler handles http operations on image manifests.