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 (
@@ -91,8 +96,7 @@ 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"},
 	}
@@ -100,7 +104,7 @@ func NewCmdLogs(f cmdutil.Factory, out io.Writer) *cobra.Command {
 	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")
@@ -108,16 +112,23 @@ func NewCmdLogs(f cmdutil.Factory, out io.Writer) *cobra.Command {
 	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
 }