From c9bb330b710b03b90b300bf4ad30e5b7c8d8eb20 Mon Sep 17 00:00:00 2001
From: Aaron Lehmann <aaron.lehmann@docker.com>
Date: Thu, 6 Aug 2015 10:34:35 -0700
Subject: [PATCH 1/2] Add a read-only mode as a configuration option

Add "readonly" under the storage/maintenance section. When this is set
to true, uploads and deletions will return 503 Service Unavailable
errors.

Document the parameter and add some unit testing.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
---
 docs/configuration.md           | 17 +++++++++---
 registry/api/v2/errors.go       | 10 +++++++
 registry/handlers/api_test.go   | 48 +++++++++++++++++++++++++++++++++
 registry/handlers/app.go        | 18 +++++++++----
 registry/handlers/blob.go       |  2 +-
 registry/handlers/blobupload.go |  8 +++---
 registry/handlers/helpers.go    | 14 ++++++++++
 registry/handlers/images.go     |  4 +--
 8 files changed, 106 insertions(+), 15 deletions(-)

diff --git a/docs/configuration.md b/docs/configuration.md
index b4080cb0..6d6d52a9 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -118,6 +118,7 @@ information about each option that appears later in this page.
           age: 168h
           interval: 24h
           dryrun: false
+        readonly: false
     auth:
       silly:
         realm: silly-realm
@@ -643,14 +644,15 @@ 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.
 
 
@@ -663,6 +665,15 @@ 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` parameter in the `maintenance` section is 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` set to true. After the garbage collection pass finishes, the registry
+may be restarted again, this time with `readonly` removed from the configuration.
+
 ### Openstack Swift
 
 This storage backend uses Openstack Swift object storage.
diff --git a/registry/api/v2/errors.go b/registry/api/v2/errors.go
index ece52a2c..97cb03e2 100644
--- a/registry/api/v2/errors.go
+++ b/registry/api/v2/errors.go
@@ -133,4 +133,14 @@ 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,
+	})
 )
diff --git a/registry/handlers/api_test.go b/registry/handlers/api_test.go
index 52a74a2b..e85ae434 100644
--- a/registry/handlers/api_test.go
+++ b/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.StatusServiceUnavailable)
+}
+
+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.StatusServiceUnavailable)
+}
+
 func httpDelete(url string) (*http.Response, error) {
 	req, err := http.NewRequest("DELETE", url, nil)
 	if err != nil {
diff --git a/registry/handlers/app.go b/registry/handlers/app.go
index 5103c5fb..d851714a 100644
--- a/registry/handlers/app.go
+++ b/registry/handlers/app.go
@@ -64,6 +64,9 @@ 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
@@ -99,13 +102,18 @@ 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 {
+			app.readOnly, ok = v.(bool)
+			if !ok {
+				panic("readonly config key must have a boolean value")
 			}
 		}
-
 	}
 
 	startUploadPurger(app, app.driver, ctxu.GetLogger(app), purgeConfig)
diff --git a/registry/handlers/blob.go b/registry/handlers/blob.go
index 4a923aa5..69c39841 100644
--- a/registry/handlers/blob.go
+++ b/registry/handlers/blob.go
@@ -35,7 +35,7 @@ func blobDispatcher(ctx *Context, r *http.Request) http.Handler {
 	return handlers.MethodHandler{
 		"GET":    http.HandlerFunc(blobHandler.GetBlob),
 		"HEAD":   http.HandlerFunc(blobHandler.GetBlob),
-		"DELETE": http.HandlerFunc(blobHandler.DeleteBlob),
+		"DELETE": mutableHandler(blobHandler.DeleteBlob, ctx),
 	}
 }
 
diff --git a/registry/handlers/blobupload.go b/registry/handlers/blobupload.go
index bbb70b59..198a8f67 100644
--- a/registry/handlers/blobupload.go
+++ b/registry/handlers/blobupload.go
@@ -23,12 +23,12 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 	}
 
 	handler := http.Handler(handlers.MethodHandler{
-		"POST":   http.HandlerFunc(buh.StartBlobUpload),
+		"POST":   mutableHandler(buh.StartBlobUpload, ctx),
 		"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),
+		"PATCH":  mutableHandler(buh.PatchBlobData, ctx),
+		"PUT":    mutableHandler(buh.PutBlobUploadComplete, ctx),
+		"DELETE": mutableHandler(buh.CancelBlobUpload, ctx),
 	})
 
 	if buh.UUID != "" {
diff --git a/registry/handlers/helpers.go b/registry/handlers/helpers.go
index 5a3c9984..9b462a19 100644
--- a/registry/handlers/helpers.go
+++ b/registry/handlers/helpers.go
@@ -7,6 +7,7 @@ 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
@@ -60,3 +61,16 @@ 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)
+	}
+}
diff --git a/registry/handlers/images.go b/registry/handlers/images.go
index e1931730..78e36a13 100644
--- a/registry/handlers/images.go
+++ b/registry/handlers/images.go
@@ -34,8 +34,8 @@ func imageManifestDispatcher(ctx *Context, r *http.Request) http.Handler {
 
 	return handlers.MethodHandler{
 		"GET":    http.HandlerFunc(imageManifestHandler.GetImageManifest),
-		"PUT":    http.HandlerFunc(imageManifestHandler.PutImageManifest),
-		"DELETE": http.HandlerFunc(imageManifestHandler.DeleteImageManifest),
+		"PUT":    mutableHandler(imageManifestHandler.PutImageManifest, ctx),
+		"DELETE": mutableHandler(imageManifestHandler.DeleteImageManifest, ctx),
 	}
 }
 

From a601f923368125f3d3f7f52f9711272be386599c Mon Sep 17 00:00:00 2001
From: Aaron Lehmann <aaron.lehmann@docker.com>
Date: Thu, 6 Aug 2015 18:02:43 -0700
Subject: [PATCH 2/2] 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           | 16 +++++++++-------
 registry/api/v2/errors.go       | 10 ----------
 registry/handlers/api_test.go   |  4 ++--
 registry/handlers/app.go        | 10 ++++++++--
 registry/handlers/blob.go       | 13 +++++++++----
 registry/handlers/blobupload.go | 21 ++++++++++++---------
 registry/handlers/helpers.go    | 14 --------------
 registry/handlers/images.go     | 13 +++++++++----
 8 files changed, 49 insertions(+), 52 deletions(-)

diff --git a/docs/configuration.md b/docs/configuration.md
index 6d6d52a9..b076191f 100644
--- a/docs/configuration.md
+++ b/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
-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` set to true. After the garbage collection pass finishes, the registry
-may be restarted again, this time with `readonly` removed from the configuration.
+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
 
diff --git a/registry/api/v2/errors.go b/registry/api/v2/errors.go
index 97cb03e2..ece52a2c 100644
--- a/registry/api/v2/errors.go
+++ b/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,
-	})
 )
diff --git a/registry/handlers/api_test.go b/registry/handlers/api_test.go
index e85ae434..0a0b264b 100644
--- a/registry/handlers/api_test.go
+++ b/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) {
diff --git a/registry/handlers/app.go b/registry/handlers/app.go
index d851714a..b11dc5b6 100644
--- a/registry/handlers/app.go
+++ b/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")
+				}
 			}
 		}
 	}
diff --git a/registry/handlers/blob.go b/registry/handlers/blob.go
index 69c39841..fb250acd 100644
--- a/registry/handlers/blob.go
+++ b/registry/handlers/blob.go
@@ -32,11 +32,16 @@ func blobDispatcher(ctx *Context, r *http.Request) http.Handler {
 		Digest:  dgst,
 	}
 
-	return handlers.MethodHandler{
-		"GET":    http.HandlerFunc(blobHandler.GetBlob),
-		"HEAD":   http.HandlerFunc(blobHandler.GetBlob),
-		"DELETE": mutableHandler(blobHandler.DeleteBlob, ctx),
+	mhandler := handlers.MethodHandler{
+		"GET":  http.HandlerFunc(blobHandler.GetBlob),
+		"HEAD": http.HandlerFunc(blobHandler.GetBlob),
 	}
+
+	if !ctx.readOnly {
+		mhandler["DELETE"] = http.HandlerFunc(blobHandler.DeleteBlob)
+	}
+
+	return mhandler
 }
 
 // blobHandler serves http blob requests.
diff --git a/registry/handlers/blobupload.go b/registry/handlers/blobupload.go
index 198a8f67..1bd33d33 100644
--- a/registry/handlers/blobupload.go
+++ b/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":   mutableHandler(buh.StartBlobUpload, ctx),
-		"GET":    http.HandlerFunc(buh.GetUploadStatus),
-		"HEAD":   http.HandlerFunc(buh.GetUploadStatus),
-		"PATCH":  mutableHandler(buh.PatchBlobData, ctx),
-		"PUT":    mutableHandler(buh.PutBlobUploadComplete, ctx),
-		"DELETE": mutableHandler(buh.CancelBlobUpload, ctx),
-	})
+	handler := handlers.MethodHandler{
+		"GET":  http.HandlerFunc(buh.GetUploadStatus),
+		"HEAD": http.HandlerFunc(buh.GetUploadStatus),
+	}
+
+	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
diff --git a/registry/handlers/helpers.go b/registry/handlers/helpers.go
index 9b462a19..5a3c9984 100644
--- a/registry/handlers/helpers.go
+++ b/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)
-	}
-}
diff --git a/registry/handlers/images.go b/registry/handlers/images.go
index 78e36a13..0aeeb6f0 100644
--- a/registry/handlers/images.go
+++ b/registry/handlers/images.go
@@ -32,11 +32,16 @@ func imageManifestDispatcher(ctx *Context, r *http.Request) http.Handler {
 		imageManifestHandler.Digest = dgst
 	}
 
-	return handlers.MethodHandler{
-		"GET":    http.HandlerFunc(imageManifestHandler.GetImageManifest),
-		"PUT":    mutableHandler(imageManifestHandler.PutImageManifest, ctx),
-		"DELETE": mutableHandler(imageManifestHandler.DeleteImageManifest, ctx),
+	mhandler := handlers.MethodHandler{
+		"GET": http.HandlerFunc(imageManifestHandler.GetImageManifest),
 	}
+
+	if !ctx.readOnly {
+		mhandler["PUT"] = http.HandlerFunc(imageManifestHandler.PutImageManifest)
+		mhandler["DELETE"] = http.HandlerFunc(imageManifestHandler.DeleteImageManifest)
+	}
+
+	return mhandler
 }
 
 // imageManifestHandler handles http operations on image manifests.