feat: allow logging output to use JSON formatter

Signed-off-by: GridexX <arsene582@gmail.com>

cmd/root.go

@@ -34,6 +34,7 @@ var (
 	noRestart           bool
 	monitorOnly         bool
 	enableLabel         bool
+	enableJsonFormatter bool
 	notifier            t.Notifier
 	timeout             time.Duration
 	lifecycleHooks      bool
@@ -96,6 +97,11 @@ func PreRun(cmd *cobra.Command, _ []string) {
 		log.SetLevel(logLevel)
 	}
 
+	enableJsonFormatter, _ = f.GetBool("json-logging")
+	if enableJsonFormatter {
+		log.SetFormatter(&log.JSONFormatter{})
+	}
+
 	scheduleSpec, _ = f.GetString("schedule")
 
 	flags.GetSecretsFromFiles(cmd)

docs/arguments.md

@@ -107,6 +107,17 @@ Environment Variable: WATCHTOWER_LOG_LEVEL
              Default: info
 ```
 
+## JSON Logging
+
+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.
+
+```text
+            Argument: --json-logging
+Environment Variable: WATCHTOWER_JSON_LOGGING
+                Type: Boolean
+             Default: false
+```
+
 ## ANSI colors
 Disable ANSI color escape codes in log output.
 

internal/flags/flags.go

@@ -86,6 +86,12 @@ func RegisterSystemFlags(rootCmd *cobra.Command) {
 		viper.GetBool("WATCHTOWER_LABEL_ENABLE"),
 		"Watch containers where the com.centurylinklabs.watchtower.enable label is true")
 
+	flags.BoolP(
+		"json-logging",
+		"j",
+		viper.GetBool("WATCHTOWER_JSON_LOGGING"),
+		"Enables the JSON log formatter for logging")
+
 	flags.BoolP(
 		"debug",
 		"d",

internal/flags/flags_test.go

@@ -183,6 +183,28 @@ func TestProcessFlagAliasesLogLevelFromEnvironment(t *testing.T) {
 	assert.Equal(t, `debug`, logLevel)
 }
 
+func TestJSONLoggingFlag(t *testing.T) {
+	cmd := new(cobra.Command)
+
+	SetDefaults()
+	RegisterDockerFlags(cmd)
+	RegisterSystemFlags(cmd)
+
+	// Ensure the default value is false
+	enableJsonFormatter, err := cmd.PersistentFlags().GetBool("json-logging")
+	require.NoError(t, err)
+
+	assert.Equal(t, false, enableJsonFormatter)
+
+	// Test with the argument
+	require.NoError(t, cmd.ParseFlags([]string{`--json-logging`}))
+	flags := cmd.Flags()
+	enableJsonFormatter, _ = flags.GetBool("json-logging")
+	require.NoError(t, err)
+	assert.Equal(t, true, enableJsonFormatter)
+
+}
+
 func TestProcessFlagAliasesSchedAndInterval(t *testing.T) {
 	logrus.StandardLogger().ExitFunc = func(_ int) { panic(`FATAL`) }
 	cmd := new(cobra.Command)