Allow a selector when retrieving logs

pkg/kubectl/cmd/logs.go

@@ -40,6 +40,9 @@ var (
 		# Return snapshot logs from pod nginx with only one container
 		kubectl logs nginx
 
+		# Return snapshot logs for the pods defined by label app=nginx
+		kubectl logs -lapp=nginx
+
 		# Return snapshot of previous terminated ruby container logs from pod web-1
 		kubectl logs -p -c ruby web-1
 
@@ -51,6 +54,8 @@ var (
 
 		# Show all logs from pod nginx written in the last hour
 		kubectl logs --since=1h nginx`)
+
+	selectorTail int64 = 10
 )
 
 const (
@@ -91,33 +96,39 @@ func NewCmdLogs(f cmdutil.Factory, out io.Writer) *cobra.Command {
 			if err := o.Validate(); err != nil {
 				cmdutil.CheckErr(cmdutil.UsageError(cmd, err.Error()))
 			}
-			_, err := o.RunLogs()
-			cmdutil.CheckErr(err)
+			cmdutil.CheckErr(o.RunLogs())
 		},
 		Aliases: []string{"log"},
 	}
 	cmd.Flags().BoolP("follow", "f", false, "Specify if the logs should be streamed.")
 	cmd.Flags().Bool("timestamps", false, "Include timestamps on each line in the log output")
 	cmd.Flags().Int64("limit-bytes", 0, "Maximum bytes of logs to return. Defaults to no limit.")
 	cmd.Flags().BoolP("previous", "p", false, "If true, print the logs for the previous instance of the container in a pod if it exists.")
-	cmd.Flags().Int64("tail", -1, "Lines of recent log file to display. Defaults to -1, showing all log lines.")
+	cmd.Flags().Int64("tail", -1, "Lines of recent log file to display. Defaults to -1 with no selector, showing all log lines otherwise 10, if a selector is provided.")
 	cmd.Flags().String("since-time", "", "Only return logs after a specific date (RFC3339). Defaults to all logs. Only one of since-time / since may be used.")
 	cmd.Flags().Duration("since", 0, "Only return logs newer than a relative duration like 5s, 2m, or 3h. Defaults to all logs. Only one of since-time / since may be used.")
 	cmd.Flags().StringP("container", "c", "", "Print the logs of this container")
 
 	cmd.Flags().Bool("interactive", false, "If true, prompt the user for input when required.")
 	cmd.Flags().MarkDeprecated("interactive", "This flag is no longer respected and there is no replacement.")
 	cmdutil.AddInclude3rdPartyFlags(cmd)
+	cmd.Flags().StringP("selector", "l", "", "Selector (label query) to filter on.")
 	return cmd
 }
 
 func (o *LogsOptions) Complete(f cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []string) error {
 	containerName := cmdutil.GetFlagString(cmd, "container")
+	selector := cmdutil.GetFlagString(cmd, "selector")
 	switch len(args) {
 	case 0:
-		return cmdutil.UsageError(cmd, logsUsageStr)
+		if len(selector) == 0 {
+			return cmdutil.UsageError(cmd, logsUsageStr)
+		}
 	case 1:
 		o.ResourceArg = args[0]
+		if len(selector) != 0 {
+			return cmdutil.UsageError(cmd, "only a selector (-l) or a POD name is allowed")
+		}
 	case 2:
 		if cmd.Flag("container").Changed {
 			return cmdutil.UsageError(cmd, "only one of -c or an inline [CONTAINER] arg is allowed")
@@ -162,18 +173,35 @@ func (o *LogsOptions) Complete(f cmdutil.Factory, out io.Writer, cmd *cobra.Comm
 	o.ClientMapper = resource.ClientMapperFunc(f.ClientForMapping)
 	o.Out = out
 
+	if len(selector) != 0 {
+		if logOptions.Follow {
+			return cmdutil.UsageError(cmd, "only one of follow (-f) or selector (-l) is allowed")
+		}
+		if len(logOptions.Container) != 0 {
+			return cmdutil.UsageError(cmd, "a container cannot be specified when using a selector (-l)")
+		}
+		if logOptions.TailLines == nil {
+			logOptions.TailLines = &selectorTail
+		}
+	}
+
 	mapper, typer := f.Object()
 	decoder := f.Decoder(true)
 	if o.Object == nil {
-		infos, err := resource.NewBuilder(mapper, typer, o.ClientMapper, decoder).
+		builder := resource.NewBuilder(mapper, typer, o.ClientMapper, decoder).
 			NamespaceParam(o.Namespace).DefaultNamespace().
-			ResourceNames("pods", o.ResourceArg).
-			SingleResourceType().
-			Do().Infos()
+			SingleResourceType()
+		if o.ResourceArg != "" {
+			builder.ResourceNames("pods", o.ResourceArg)
+		}
+		if selector != "" {
+			builder.ResourceTypes("pods").SelectorParam(selector)
+		}
+		infos, err := builder.Do().Infos()
 		if err != nil {
 			return err
 		}
-		if len(infos) != 1 {
+		if selector == "" && len(infos) != 1 {
 			return errors.New("expected a resource")
 		}
 		o.Object = infos[0].Object
@@ -183,9 +211,6 @@ func (o *LogsOptions) Complete(f cmdutil.Factory, out io.Writer, cmd *cobra.Comm
 }
 
 func (o LogsOptions) Validate() error {
-	if len(o.ResourceArg) == 0 {
-		return errors.New("a pod must be specified")
-	}
 	logsOptions, ok := o.Options.(*api.PodLogOptions)
 	if !ok {
 		return errors.New("unexpected logs options object")
@@ -198,17 +223,32 @@ func (o LogsOptions) Validate() error {
 }
 
 // RunLogs retrieves a pod log
-func (o LogsOptions) RunLogs() (int64, error) {
-	req, err := o.LogsForObject(o.Object, o.Options)
+func (o LogsOptions) RunLogs() error {
+	switch t := o.Object.(type) {
+	case *api.PodList:
+		for _, p := range t.Items {
+			if err := o.getLogs(&p); err != nil {
+				return err
+			}
+		}
+		return nil
+	default:
+		return o.getLogs(o.Object)
+	}
+}
+
+func (o LogsOptions) getLogs(obj runtime.Object) error {
+	req, err := o.LogsForObject(obj, o.Options)
 	if err != nil {
-		return 0, err
+		return err
 	}
 
 	readCloser, err := req.Stream()
 	if err != nil {
-		return 0, err
+		return err
 	}
 	defer readCloser.Close()
 
-	return io.Copy(o.Out, readCloser)
+	_, err = io.Copy(o.Out, readCloser)
+	return err
 }