karma: add ability to configure log format

Add a rudimentary switch which would let users switch between different
formats used for logging. This is needed so that software such as
`logstash` could easily understand the structure of log messages and
index them accordingly.

internal/config/config.go

@@ -70,6 +70,8 @@ func init() {
 	pflag.Bool("log.config", true, "Log used configuration to log on startup")
 	pflag.String("log.level", "info",
 		"Log level, one of: debug, info, warning, error, fatal and panic")
+	pflag.String("log.format", "text",
+		"Log format, one of: text, json")
 
 	pflag.StringSlice("receivers.keep", []string{},
 		"List of receivers to keep, all alerts with different receivers will be ignored")
@@ -159,6 +161,7 @@ func (config *configSchema) Read() {
 	config.Listen.Prefix = v.GetString("listen.prefix")
 	config.Log.Config = v.GetBool("log.config")
 	config.Log.Level = v.GetString("log.level")
+	config.Log.Format = v.GetString("log.format")
 	config.Receivers.Keep = v.GetStringSlice("receivers.keep")
 	config.Receivers.Strip = v.GetStringSlice("receivers.strip")
 	config.Sentry.Private = v.GetString("sentry.private")

internal/config/models.go

@@ -82,6 +82,7 @@ type configSchema struct {
 	Log struct {
 		Config bool
 		Level  string
+		Format string
 	}
 	JIRA      []jiraRule
 	Receivers struct {

main.go

@@ -158,6 +158,15 @@ func setupLogger() {
 	default:
 		log.Fatalf("Unknown log level '%s'", config.Config.Log.Level)
 	}
+
+	switch config.Config.Log.Format {
+	case "text":
+		log.SetFormatter(&log.TextFormatter{})
+	case "json":
+		log.SetFormatter(&log.JSONFormatter{})
+	default:
+		log.Fatalf("Unknown log format '%s'", config.Config.Log.Format)
+	}
 }
 
 func main() {