Add --watch to get command

pkg/kubectl/cmd/get.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/kubectl"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
 	"github.com/spf13/cobra"
@@ -50,7 +51,7 @@ Examples:
 			mapping, namespace, name := ResourceOrTypeFromArgs(cmd, args, f.Mapper)
 
 			selector := GetFlagString(cmd, "selector")
-			labels, err := labels.ParseSelector(selector)
+			labelSelector, err := labels.ParseSelector(selector)
 			checkErr(err)
 
 			client, err := f.Client(cmd, mapping)
@@ -68,12 +69,26 @@ Examples:
 			printer, err := kubectl.GetPrinter(outputVersion, outputFormat, templateFile, defaultPrinter)
 			checkErr(err)
 
-			obj, err := kubectl.NewRESTHelper(client, mapping).Get(namespace, name, labels)
+			restHelper := kubectl.NewRESTHelper(client, mapping)
+			obj, err := restHelper.Get(namespace, name, labelSelector)
 			checkErr(err)
 
 			if err := printer.PrintObj(obj, out); err != nil {
 				checkErr(fmt.Errorf("Unable to output the provided object: %v", err))
 			}
+
+			if GetFlagBool(cmd, "watch") {
+				vi, err := latest.InterfacesFor(outputVersion)
+				checkErr(err)
+
+				rv, err := vi.MetadataAccessor.ResourceVersion(obj)
+				checkErr(err)
+
+				w, err := restHelper.Watch(namespace, rv, labelSelector, labels.Set{}.AsSelector())
+				checkErr(err)
+
+				kubectl.WatchLoop(w, printer, out)
+			}
 		},
 	}
 	cmd.Flags().StringP("output", "o", "", "Output format: json|yaml|template|templatefile")
@@ -81,5 +96,6 @@ Examples:
 	cmd.Flags().Bool("no-headers", false, "When using the default output, don't print headers")
 	cmd.Flags().StringP("template", "t", "", "Template string or path to template file to use when --output=template or --output=templatefile")
 	cmd.Flags().StringP("selector", "l", "", "Selector (label query) to filter on")
+	cmd.Flags().BoolP("watch", "w", false, "After listing/getting the requested object, watch for changes.")
 	return cmd
 }

pkg/kubectl/resource_printer.go

@@ -154,10 +154,14 @@ type handlerEntry struct {
 	printFunc reflect.Value
 }
 
-// HumanReadablePrinter is an implementation of ResourcePrinter which attempts to provide more elegant output.
+// HumanReadablePrinter is an implementation of ResourcePrinter which attempts to provide
+// more elegant output. It is not threadsafe, but you may call PrintObj repeatedly; headers
+// will only be printed if the object type changes. This makes it useful for printing items
+// recieved from watches.
 type HumanReadablePrinter struct {
 	handlerMap map[reflect.Type]*handlerEntry
 	noHeaders  bool
+	lastType   reflect.Type
 }
 
 // IsVersioned returns false-- human readable printers do not make versioned output.
@@ -348,9 +352,11 @@ func printEventList(list *api.EventList, w io.Writer) error {
 func (h *HumanReadablePrinter) PrintObj(obj runtime.Object, output io.Writer) error {
 	w := tabwriter.NewWriter(output, 20, 5, 3, ' ', 0)
 	defer w.Flush()
-	if handler := h.handlerMap[reflect.TypeOf(obj)]; handler != nil {
-		if !h.noHeaders {
+	t := reflect.TypeOf(obj)
+	if handler := h.handlerMap[t]; handler != nil {
+		if !h.noHeaders && t != h.lastType {
 			h.printHeader(handler.columns, w)
+			h.lastType = t
 		}
 		args := []reflect.Value{reflect.ValueOf(obj), reflect.ValueOf(w)}
 		resultValue := handler.printFunc.Call(args)[0]

pkg/kubectl/resthelper.go

@@ -20,6 +20,7 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/meta"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
 )
 
 // RESTHelper provides methods for retrieving or mutating a RESTful
@@ -49,6 +50,17 @@ func (m *RESTHelper) Get(namespace, name string, selector labels.Selector) (runt
 	return m.RESTClient.Get().Path(m.Resource).Namespace(namespace).Path(name).SelectorParam("labels", selector).Do().Get()
 }
 
+func (m *RESTHelper) Watch(namespace, resourceVersion string, labelSelector, fieldSelector labels.Selector) (watch.Interface, error) {
+	return m.RESTClient.Get().
+		Path("watch").
+		Path(m.Resource).
+		Namespace(namespace).
+		Param("resourceVersion", resourceVersion).
+		SelectorParam("labels", labelSelector).
+		SelectorParam("fields", fieldSelector).
+		Watch()
+}
+
 func (m *RESTHelper) Delete(namespace, name string) error {
 	return m.RESTClient.Delete().Path(m.Resource).Namespace(namespace).Path(name).Do().Error()
 }

pkg/kubectl/watchloop.go

@@ -0,0 +1,47 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubectl
+
+import (
+	"io"
+	"os"
+	"os/signal"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
+)
+
+// WatchLoop loops, writing objects in the events from w to printer.
+// If user sends interrupt signal, shut down cleanly. Otherwise, never return.
+func WatchLoop(w watch.Interface, printer ResourcePrinter, out io.Writer) {
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, os.Interrupt)
+	defer signal.Stop(signals)
+	for {
+		select {
+		case event, ok := <-w.ResultChan():
+			if !ok {
+				return
+			}
+			// TODO: need to print out added/modified/deleted!
+			if err := printer.PrintObj(event.Object, out); err != nil {
+				w.Stop()
+			}
+		case <-signals:
+			w.Stop()
+		}
+	}
+}