switch to log-format flag

cmd/root.go

@@ -1,6 +1,7 @@
 package cmd
 
 import (
+	"errors"
 	"math"
 	"net/http"
 	"os"
@@ -34,7 +35,6 @@ var (
 	noRestart      bool
 	monitorOnly    bool
 	enableLabel    bool
-	enableJsonFormatter bool
 	notifier       t.Notifier
 	timeout        time.Duration
 	lifecycleHooks bool
@@ -77,31 +77,11 @@ func Execute() {
 // PreRun is a lifecycle hook that runs before the command is executed.
 func PreRun(cmd *cobra.Command, _ []string) {
 	f := cmd.PersistentFlags()
+	if err := flags.SetupLogging(f); err != nil {
+		log.Fatalf("Failed to initialize logging: %s", err.Error())
+	}
 	flags.ProcessFlagAliases(f)
 
-	if enabled, _ := f.GetBool("no-color"); enabled {
-		log.SetFormatter(&log.TextFormatter{
-			DisableColors: true,
-		})
-	} else {
-		// enable logrus built-in support for https://bixense.com/clicolors/
-		log.SetFormatter(&log.TextFormatter{
-			EnvironmentOverrideColors: true,
-		})
-	}
-
-	rawLogLevel, _ := f.GetString(`log-level`)
-	if logLevel, err := log.ParseLevel(rawLogLevel); err != nil {
-		log.Fatalf("Invalid log level: %s", err.Error())
-	} else {
-		log.SetLevel(logLevel)
-	}
-
-	enableJsonFormatter, _ = f.GetBool("json-logging")
-	if enableJsonFormatter {
-		log.SetFormatter(&log.JSONFormatter{})
-	}
-
 	scheduleSpec, _ = f.GetString("schedule")
 
 	flags.GetSecretsFromFiles(cmd)
@@ -205,7 +185,7 @@ func Run(c *cobra.Command, names []string) {
 		httpAPI.RegisterHandler(metricsHandler.Path, metricsHandler.Handle)
 	}
 
-	if err := httpAPI.Start(enableUpdateAPI && !unblockHTTPAPI); err != nil && err != http.ErrServerClosed {
+	if err := httpAPI.Start(enableUpdateAPI && !unblockHTTPAPI); err != nil && !errors.Is(err, http.ErrServerClosed) {
 		log.Error("failed to start API", err)
 	}
 

docs/arguments.md

@@ -107,15 +107,15 @@ Environment Variable: WATCHTOWER_LOG_LEVEL
              Default: info
 ```
 
-## JSON Logging
+## Logging format
 
-Enables the JSON log formatter for logging, changing the log output to JSON format. By default, the log output follows the standard text-based format.
+Sets what logging format to use for console output.
 
 ```text
-            Argument: --json-logging
+            Argument: --log-format, -l
-Environment Variable: WATCHTOWER_JSON_LOGGING
+Environment Variable: WATCHTOWER_LOG_FORMAT
-                Type: Boolean
+     Possible values: Auto, LogFmt, Pretty or JSON
-             Default: false
+             Default: Auto
 ```
 
 ## ANSI colors

internal/flags/flags.go

@@ -86,11 +86,11 @@ func RegisterSystemFlags(rootCmd *cobra.Command) {
 		viper.GetBool("WATCHTOWER_LABEL_ENABLE"),
 		"Watch containers where the com.centurylinklabs.watchtower.enable label is true")
 
-	flags.BoolP(
+	flags.StringP(
-		"json-logging",
+		"log-format",
-		"j",
+		"l",
-		viper.GetBool("WATCHTOWER_JSON_LOGGING"),
+		viper.GetString("WATCHTOWER_LOG_FORMAT"),
-		"Enables the JSON log formatter for logging")
+		"Sets what logging format to use for console output. Possible values: Auto, LogFmt, Pretty, JSON")
 
 	flags.BoolP(
 		"debug",
@@ -385,6 +385,7 @@ func SetDefaults() {
 	viper.SetDefault("WATCHTOWER_NOTIFICATION_EMAIL_SUBJECTTAG", "")
 	viper.SetDefault("WATCHTOWER_NOTIFICATION_SLACK_IDENTIFIER", "watchtower")
 	viper.SetDefault("WATCHTOWER_LOG_LEVEL", "info")
+	viper.SetDefault("WATCHTOWER_LOG_FORMAT", "auto")
 }
 
 // EnvConfig translates the command-line options into environment variables
@@ -583,6 +584,46 @@ func ProcessFlagAliases(flags *pflag.FlagSet) {
 
 }
 
+// SetupLogging reads only the flags that is needed to set up logging and applies them to the global logger
+func SetupLogging(f *pflag.FlagSet) error {
+	logFormat, _ := f.GetString(`log-format`)
+	noColor, _ := f.GetBool("no-color")
+
+	switch strings.ToLower(logFormat) {
+	case "auto":
+		// This will either use the "pretty" or "logfmt" format, based on whether the standard out is connected to a TTY
+		log.SetFormatter(&log.TextFormatter{
+			DisableColors: noColor,
+			// enable logrus built-in support for https://bixense.com/clicolors/
+			EnvironmentOverrideColors: true,
+		})
+	case "json":
+		log.SetFormatter(&log.JSONFormatter{})
+	case "logfmt":
+		log.SetFormatter(&log.TextFormatter{
+			DisableColors: true,
+			FullTimestamp: true,
+		})
+	case "pretty":
+		log.SetFormatter(&log.TextFormatter{
+			// "Pretty" format combined with `--no-color` will only change the timestamp to the time since start
+			ForceColors:   !noColor,
+			FullTimestamp: false,
+		})
+	default:
+		return fmt.Errorf("invalid log format: %s", logFormat)
+	}
+
+	rawLogLevel, _ := f.GetString(`log-level`)
+	if logLevel, err := log.ParseLevel(rawLogLevel); err != nil {
+		return fmt.Errorf("invalid log level: %e", err)
+	} else {
+		log.SetLevel(logLevel)
+	}
+
+	return nil
+}
+
 func flagIsEnabled(flags *pflag.FlagSet, name string) bool {
 	value, err := flags.GetBool(name)
 	if err != nil {

internal/flags/flags_test.go

@@ -183,26 +183,55 @@ func TestProcessFlagAliasesLogLevelFromEnvironment(t *testing.T) {
 	assert.Equal(t, `debug`, logLevel)
 }
 
-func TestJSONLoggingFlag(t *testing.T) {
+func TestLogFormatFlag(t *testing.T) {
 	cmd := new(cobra.Command)
 
 	SetDefaults()
 	RegisterDockerFlags(cmd)
 	RegisterSystemFlags(cmd)
 
-	// Ensure the default value is false
+	// Ensure the default value is Auto
-	enableJsonFormatter, err := cmd.PersistentFlags().GetBool("json-logging")
+	require.NoError(t, cmd.ParseFlags([]string{}))
-	require.NoError(t, err)
+	require.NoError(t, SetupLogging(cmd.Flags()))
+	assert.IsType(t, &logrus.TextFormatter{}, logrus.StandardLogger().Formatter)
 
-	assert.Equal(t, false, enableJsonFormatter)
+	// Test JSON format
+	require.NoError(t, cmd.ParseFlags([]string{`--log-format`, `JSON`}))
+	require.NoError(t, SetupLogging(cmd.Flags()))
+	assert.IsType(t, &logrus.JSONFormatter{}, logrus.StandardLogger().Formatter)
 
-	// Test with the argument
+	// Test Pretty format
-	require.NoError(t, cmd.ParseFlags([]string{`--json-logging`}))
+	require.NoError(t, cmd.ParseFlags([]string{`--log-format`, `pretty`}))
-	flags := cmd.Flags()
+	require.NoError(t, SetupLogging(cmd.Flags()))
-	enableJsonFormatter, _ = flags.GetBool("json-logging")
+	assert.IsType(t, &logrus.TextFormatter{}, logrus.StandardLogger().Formatter)
-	require.NoError(t, err)
+	textFormatter, ok := (logrus.StandardLogger().Formatter).(*logrus.TextFormatter)
-	assert.Equal(t, true, enableJsonFormatter)
+	assert.True(t, ok)
+	assert.True(t, textFormatter.ForceColors)
+	assert.False(t, textFormatter.FullTimestamp)
 
+	// Test LogFmt format
+	require.NoError(t, cmd.ParseFlags([]string{`--log-format`, `logfmt`}))
+	require.NoError(t, SetupLogging(cmd.Flags()))
+	textFormatter, ok = (logrus.StandardLogger().Formatter).(*logrus.TextFormatter)
+	assert.True(t, ok)
+	assert.True(t, textFormatter.DisableColors)
+	assert.True(t, textFormatter.FullTimestamp)
+
+	// Test invalid format
+	require.NoError(t, cmd.ParseFlags([]string{`--log-format`, `cowsay`}))
+	require.Error(t, SetupLogging(cmd.Flags()))
+}
+
+func TestLogLevelFlag(t *testing.T) {
+	cmd := new(cobra.Command)
+
+	SetDefaults()
+	RegisterDockerFlags(cmd)
+	RegisterSystemFlags(cmd)
+
+	// Test invalid format
+	require.NoError(t, cmd.ParseFlags([]string{`--log-level`, `gossip`}))
+	require.Error(t, SetupLogging(cmd.Flags()))
 }
 
 func TestProcessFlagAliasesSchedAndInterval(t *testing.T) {