Don't pretty-print by default. Saves an allocation (or more) and a copy.

pkg/apiserver/api_installer.go

@@ -409,6 +409,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.GET(action.Path).To(handler).
 				Filter(m).
 				Doc("read the specified "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("read"+kind).
 				Produces(append(storageMeta.ProducesMIMETypes(action.Verb), "application/json")...).
 				Returns(http.StatusOK, "OK", versionedObject).
@@ -424,6 +425,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.GET(action.Path).To(ListResource(lister, watcher, reqScope, false, a.minRequestTimeout)).
 				Filter(m).
 				Doc("list objects of kind "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("list"+kind).
 				Produces("application/json").
 				Returns(http.StatusOK, "OK", versionedList).
@@ -443,6 +445,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.PUT(action.Path).To(UpdateResource(updater, reqScope, a.group.Typer, admit)).
 				Filter(m).
 				Doc("replace the specified "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("replace"+kind).
 				Produces(append(storageMeta.ProducesMIMETypes(action.Verb), "application/json")...).
 				Returns(http.StatusOK, "OK", versionedObject).
@@ -454,6 +457,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.PATCH(action.Path).To(PatchResource(patcher, reqScope, a.group.Typer, admit, mapping.ObjectConvertor)).
 				Filter(m).
 				Doc("partially update the specified "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Consumes(string(api.JSONPatchType), string(api.MergePatchType), string(api.StrategicMergePatchType)).
 				Operation("patch"+kind).
 				Produces(append(storageMeta.ProducesMIMETypes(action.Verb), "application/json")...).
@@ -472,6 +476,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.POST(action.Path).To(handler).
 				Filter(m).
 				Doc("create a "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("create"+kind).
 				Produces(append(storageMeta.ProducesMIMETypes(action.Verb), "application/json")...).
 				Returns(http.StatusOK, "OK", versionedObject).
@@ -483,6 +488,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.DELETE(action.Path).To(DeleteResource(gracefulDeleter, isGracefulDeleter, reqScope, admit)).
 				Filter(m).
 				Doc("delete a "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("delete"+kind).
 				Produces(append(storageMeta.ProducesMIMETypes(action.Verb), "application/json")...).
 				Writes(versionedStatus).
@@ -497,6 +503,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.GET(action.Path).To(ListResource(lister, watcher, reqScope, true, a.minRequestTimeout)).
 				Filter(m).
 				Doc("watch changes to an object of kind "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("watch"+kind).
 				Produces("application/json").
 				Returns(http.StatusOK, "OK", watchjson.WatchEvent{}).
@@ -511,6 +518,7 @@ func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storag
 			route := ws.GET(action.Path).To(ListResource(lister, watcher, reqScope, true, a.minRequestTimeout)).
 				Filter(m).
 				Doc("watch individual changes to a list of "+kind).
+				Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
 				Operation("watch"+kind+"list").
 				Produces("application/json").
 				Returns(http.StatusOK, "OK", watchjson.WatchEvent{}).

pkg/apiserver/apiserver.go

@@ -273,32 +273,49 @@ func write(statusCode int, apiVersion string, codec runtime.Codec, object runtim
 		io.Copy(writer, out)
 		return
 	}
-	writeJSON(statusCode, codec, object, w)
+	writeJSON(statusCode, codec, object, w, isPrettyPrint(req))
+}
+
+func isPrettyPrint(req *http.Request) bool {
+	pp := req.URL.Query().Get("pretty")
+	if len(pp) > 0 {
+		pretty, _ := strconv.ParseBool(pp)
+		return pretty
+	}
+	userAgent := req.UserAgent()
+	// This covers basic all browers and cli http tools
+	if strings.HasPrefix(userAgent, "curl") || strings.HasPrefix(userAgent, "Wget") || strings.HasPrefix(userAgent, "Mozilla/5.0") {
+		return true
+	}
+	return false
 }
 
 // writeJSON renders an object as JSON to the response.
-func writeJSON(statusCode int, codec runtime.Codec, object runtime.Object, w http.ResponseWriter) {
+func writeJSON(statusCode int, codec runtime.Codec, object runtime.Object, w http.ResponseWriter, pretty bool) {
 	output, err := codec.Encode(object)
 	if err != nil {
 		errorJSONFatal(err, codec, w)
 		return
 	}
-	// PR #2243: Pretty-print JSON by default.
+	if pretty {
-	formatted := &bytes.Buffer{}
+		// PR #2243: Pretty-print JSON by default.
-	err = json.Indent(formatted, output, "", "  ")
+		formatted := &bytes.Buffer{}
-	if err != nil {
+		err = json.Indent(formatted, output, "", "  ")
-		errorJSONFatal(err, codec, w)
+		if err != nil {
-		return
+			errorJSONFatal(err, codec, w)
+			return
+		}
+		output = formatted.Bytes()
 	}
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(statusCode)
-	w.Write(formatted.Bytes())
+	w.Write(output)
 }
 
 // errorJSON renders an error to the response. Returns the HTTP status code of the error.
 func errorJSON(err error, codec runtime.Codec, w http.ResponseWriter) int {
 	status := errToAPIStatus(err)
-	writeJSON(status.Code, codec, status, w)
+	writeJSON(status.Code, codec, status, w, true)
 	return status.Code
 }
 

pkg/apiserver/apiserver_test.go

@@ -2239,7 +2239,7 @@ func (*UnregisteredAPIObject) IsAnAPIObject() {}
 
 func TestWriteJSONDecodeError(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		writeJSON(http.StatusOK, codec, &UnregisteredAPIObject{"Undecodable"}, w)
+		writeJSON(http.StatusOK, codec, &UnregisteredAPIObject{"Undecodable"}, w, false)
 	}))
 	defer server.Close()
 	status := expectApiStatus(t, "GET", server.URL, nil, http.StatusInternalServerError)

pkg/apiserver/proxy.go

@@ -111,7 +111,7 @@ func (r *ProxyHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	if err != nil {
 		httplog.LogOf(req, w).Addf("Error getting ResourceLocation: %v", err)
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		httpCode = status.Code
 		return
 	}
@@ -146,7 +146,7 @@ func (r *ProxyHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	newReq, err := http.NewRequest(req.Method, location.String(), req.Body)
 	if err != nil {
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		notFound(w, req)
 		httpCode = status.Code
 		return
@@ -196,11 +196,10 @@ func (r *ProxyHandler) tryUpgrade(w http.ResponseWriter, req, newReq *http.Reque
 	if !httpstream.IsUpgradeRequest(req) {
 		return false
 	}
-
 	backendConn, err := dialURL(location, transport)
 	if err != nil {
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		return true
 	}
 	defer backendConn.Close()
@@ -211,14 +210,14 @@ func (r *ProxyHandler) tryUpgrade(w http.ResponseWriter, req, newReq *http.Reque
 	requestHijackedConn, _, err := w.(http.Hijacker).Hijack()
 	if err != nil {
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		return true
 	}
 	defer requestHijackedConn.Close()
 
 	if err = newReq.Write(backendConn); err != nil {
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		return true
 	}
 

pkg/apiserver/redirect.go

@@ -82,7 +82,7 @@ func (r *RedirectHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	location, _, err := redirector.ResourceLocation(ctx, id)
 	if err != nil {
 		status := errToAPIStatus(err)
-		writeJSON(status.Code, r.codec, status, w)
+		writeJSON(status.Code, r.codec, status, w, true)
 		httpCode = status.Code
 		return
 	}

pkg/apiserver/resthandler.go

@@ -505,7 +505,7 @@ func UpdateResource(r rest.Updater, scope RequestScope, typer runtime.ObjectType
 		if wasCreated {
 			status = http.StatusCreated
 		}
-		writeJSON(status, scope.Codec, result, w)
+		writeJSON(status, scope.Codec, result, w, isPrettyPrint(req.Request))
 	}
 }