Add --logfile-path flag to write logs to file

Author: prydie

pkg/log/log.go

@@ -26,6 +26,7 @@ import (
 var (
 	lvlString     = "info"
 	logJSON       = false
+	logfilePath   = ""
 	config        *zap.Config
 	mu            sync.Mutex
 	glogVerbosity string
@@ -34,6 +35,7 @@ var (
 func init() {
 	flag.StringVar(&lvlString, "log-level", lvlString, "Adjusts the level of the logs that will be omitted.")
 	flag.BoolVar(&logJSON, "log-json", logJSON, "Log in json format.")
+	flag.StringVar(&logfilePath, "logfile-path", "", "If specified, write log messages to a file at this path.")
 	_ = flag.String("v", "", "For glog backwards compat. Does nothing.")
 }
 
@@ -69,6 +71,10 @@ func Logger() *zap.Logger {
 		cfg = zap.NewProductionConfig()
 	}
 
+	if len(logfilePath) > 0 {
+		cfg.OutputPaths = append(cfg.OutputPaths, logfilePath)
+	}
+
 	if config == nil {
 		config = &cfg
 		if level, err := levelFromString(lvlString); err == nil {