tetra: fix getevents --output flag

When using same local flag for different subcommands, binding to the
global configuration will erase previous values with the value of the
last command's flag registered. See spf13/viper#233.

Using a global set of variables to store the flags value of the
command solves the issue. Also add a local variable to store the value
of the output flag of the tracingpolicy list subcommand.

We may want to avoid the usage of the global configuration and using
viper.BindPFlags in the future to avoid this issue to appear again.

Also add checks on the value of flags that are restricted to certain
values.

Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>

cmd/tetra/getevents/getevents.go

@@ -38,6 +38,19 @@ redirection of events to the stdin. Examples:
   # Include only process and parent.pod fields
   %[1]s getevents -f process,parent.pod`
 
+var (
+	output        string
+	color         string
+	includeFields []string
+	excludeFields []string
+	namespaces    []string
+	processes     []string
+	pods          []string
+	host          bool
+	timestamps    bool
+	ttyEncode     string
+)
+
 // GetEncoder returns an encoder for an event stream based on configuration options.
 var GetEncoder = func(w io.Writer, colorMode encoder.ColorMode, timestamps bool, compact bool, tty string) encoder.EventEncoder {
 	if tty != "" {
@@ -51,11 +64,6 @@ var GetEncoder = func(w io.Writer, colorMode encoder.ColorMode, timestamps bool,
 
 // GetFilter returns a filter for an event stream based on configuration options.
 var GetFilter = func() *tetragon.Filter {
-	host := viper.GetBool("host")
-	namespaces := viper.GetStringSlice("namespace")
-	processes := viper.GetStringSlice("process")
-	pods := viper.GetStringSlice("pod")
-
 	if host {
 		// Host events can be matched by an empty namespace string.
 		namespaces = append(namespaces, "")
@@ -106,19 +114,12 @@ func getRequest(includeFields, excludeFields []string, filter *tetragon.Filter)
 }
 
 func getEvents(ctx context.Context, client tetragon.FineGuidanceSensorsClient) {
-	timestamps := viper.GetBool("timestamps")
-	compact := viper.GetString(common.KeyOutput) == "compact"
-	colorMode := encoder.ColorMode(viper.GetString(common.KeyColor))
-	includeFields := viper.GetStringSlice("include-fields")
-	excludeFields := viper.GetStringSlice("exclude-fields")
-	tty := viper.GetString(common.KeyTty)
-
 	request := getRequest(includeFields, excludeFields, GetFilter())
 	stream, err := client.GetEvents(ctx, request)
 	if err != nil {
 		logger.GetLogger().WithError(err).Fatal("Failed to call GetEvents")
 	}
-	eventEncoder := GetEncoder(os.Stdout, colorMode, timestamps, compact, tty)
+	eventEncoder := GetEncoder(os.Stdout, encoder.ColorMode(color), timestamps, output == "compact", ttyEncode)
 	for {
 		res, err := stream.Recv()
 		if err != nil {
@@ -138,6 +139,15 @@ func New() *cobra.Command {
 		Use:   "getevents",
 		Short: "Print events",
 		Long:  fmt.Sprintf(DocLong, "tetra"),
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			if output != "json" && output != "compact" {
+				return fmt.Errorf("invalid value for %q flag: %s", common.KeyOutput, output)
+			}
+			if color != "auto" && color != "always" && color != "never" {
+				return fmt.Errorf("invalid value for %q flag: %s", "color", color)
+			}
+			return nil
+		},
 		Run: func(cmd *cobra.Command, args []string) {
 			fi, _ := os.Stdin.Stat()
 			if fi.Mode()&os.ModeNamedPipe != 0 {
@@ -151,16 +161,15 @@ func New() *cobra.Command {
 	}
 
 	flags := cmd.Flags()
-	flags.StringP(common.KeyOutput, "o", "json", "Output format. json or compact")
-	flags.String("color", "auto", "Colorize compact output. auto, always, or never")
-	flags.StringSliceP("include-fields", "f", nil, "Include only fields in events")
-	flags.StringSliceP("exclude-fields", "F", nil, "Exclude fields from events")
-	flags.StringSliceP("namespace", "n", nil, "Get events by Kubernetes namespaces")
-	flags.StringSlice("process", nil, "Get events by process name regex")
-	flags.StringSlice("pod", nil, "Get events by pod name regex")
-	flags.Bool("host", false, "Get host events")
-	flags.Bool("timestamps", false, "Include timestamps in compact output")
-	flags.StringP("tty-encode", "t", "", "Encode terminal data by file path (all other events will be ignored)")
-	viper.BindPFlags(flags)
+	flags.StringVarP(&output, common.KeyOutput, "o", "json", "Output format. json or compact")
+	flags.StringVar(&color, "color", "auto", "Colorize compact output. auto, always, or never")
+	flags.StringSliceVarP(&includeFields, "include-fields", "f", nil, "Include only fields in events")
+	flags.StringSliceVarP(&excludeFields, "exclude-fields", "F", nil, "Exclude fields from events")
+	flags.StringSliceVarP(&namespaces, "namespace", "n", nil, "Get events by Kubernetes namespaces")
+	flags.StringSliceVar(&processes, "process", nil, "Get events by process name regex")
+	flags.StringSliceVar(&pods, "pod", nil, "Get events by pod name regex")
+	flags.BoolVar(&host, "host", false, "Get host events")
+	flags.BoolVar(&timestamps, "timestamps", false, "Include timestamps in compact output")
+	flags.StringVarP(&ttyEncode, "tty-encode", "t", "", "Encode terminal data by file path (all other events will be ignored)")
 	return &cmd
 }

cmd/tetra/tracingpolicy/tracingpolicy.go

@@ -45,26 +45,25 @@ func New() *cobra.Command {
 		},
 	}
 
+	var tpListOutputFlag string
 	tpListCmd := &cobra.Command{
 		Use:   "list",
 		Short: "list tracing policies",
 		Args:  cobra.ExactArgs(0),
-		Run: func(cmd *cobra.Command, args []string) {
-			output := viper.GetString(common.KeyOutput)
-			switch output {
-			case "json", "text":
-				// valid
-			default:
-				logger.GetLogger().WithField(common.KeyOutput, output).Fatal("invalid output flag")
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			if tpListOutputFlag != "json" && tpListOutputFlag != "text" {
+				return fmt.Errorf("invalid value for %q flag: %s", common.KeyOutput, tpListOutputFlag)
 			}
+			return nil
+		},
+		Run: func(cmd *cobra.Command, args []string) {
 			common.CliRun(func(ctx context.Context, cli tetragon.FineGuidanceSensorsClient) {
-				listTracingPolicies(ctx, cli, output)
+				listTracingPolicies(ctx, cli, tpListOutputFlag)
 			})
 		},
 	}
 	tpListFlags := tpListCmd.Flags()
-	tpListFlags.StringP(common.KeyOutput, "o", "text", "Output format. json or text")
-	viper.BindPFlags(tpListFlags)
+	tpListFlags.StringVarP(&tpListOutputFlag, common.KeyOutput, "o", "text", "Output format. text or json")
 
 	tpGenerateCmd := &cobra.Command{
 		Use:   "generate",