rework on logger + fix the program exit + rename file if errors in json parsing

main.go

@@ -77,8 +77,8 @@ func GetOutboxPath(iniFile *ini.File) (string, error) {
 }
 
 func main() {
-	var logger log.Logger
+	logger := log.NewLogfmtLogger(os.Stdout)
-	logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
+	logger = level.NewFilter(logger, level.AllowInfo())
 	logger = log.With(logger, "ts", log.DefaultTimestampUTC, "caller", log.DefaultCaller, "service", "mailsrv")
 
 	iniFile, err := LoadIni()

services/sender.go

@@ -1,6 +1,7 @@
 package services
 
 import (
+	"fmt"
 	cfg "mailsrv/config"
 	"mailsrv/mail"
 	"mailsrv/runtime"
@@ -19,6 +20,7 @@ import (
 const (
 	TickerInterval time.Duration = 10 * time.Second
 	JSONSuffix     string        = ".json"
+	ErrorSuffix    string        = ".err"
 )
 
 type Sender struct {
@@ -41,23 +43,25 @@ func NewSender(logger log.Logger, config cfg.SMTPConfig, outboxPath string) Send
 
 func (s Sender) SendMail(email mail.Email) error {
 	auth := smtp.PlainAuth("", s.smtpConfig.User, s.smtpConfig.Password, s.smtpConfig.Url)
-	s.logger.Log("action", "authentication succeed")
+	level.Debug(s.logger).Log("msg", "SMTP authentication succeed")
 
 	if err := smtp.SendMail(s.smtpConfig.GetFullUrl(), auth, email.Sender, email.Receivers, email.Generate()); err != nil {
 		level.Error(s.logger).Log("msg", "error while sending email", "err", err)
 		return err
 	}
 
-	s.logger.Log("msg", "mail send successfully")
+	level.Debug(s.logger).Log("msg", "mail send successfully")
 	return nil
 }
 
 // watchOutbox reads the `outbox` directory every `TickInterval` and put JSON format e-mail in the queue
 func (s Sender) watchOutbox() {
+	s.logger.Log("msg", "start watching outbox directory", "outbox", s.outboxPath)
 	ticker := time.NewTicker(TickerInterval)
+
 	go func() {
 		for _ = range ticker.C {
-			s.logger.Log("action", "retrieving json e-mail format...", "path", s.outboxPath)
+			level.Debug(s.logger).Log("action", "retrieving json e-mail format...", "path", s.outboxPath)
 
 			files, err := os.ReadDir(s.outboxPath)
 			if err != nil && !os.IsExist(err) {
@@ -71,7 +75,7 @@ func (s Sender) watchOutbox() {
 					s.queue.Add(path.Join(s.outboxPath, filename))
 					continue
 				}
-				level.Warn(s.logger).Log("msg", "incorrect suffix", "filename", filename)
+				level.Debug(s.logger).Log("msg", "incorrect suffix", "filename", filename)
 			}
 		}
 	}()
@@ -87,20 +91,31 @@ func (s Sender) processNextEmail() bool {
 
 	path, ok := item.(string)
 	if !ok {
-		level.Error(s.logger).Log("msg", "unable to cast queue item into mail.Email")
+		level.Error(s.logger).Log("msg", "unable to cast queue item into mail.Email", "item", item)
 		return true
 	}
 
 	email, err := mail.FromJSON(path)
 	if err != nil {
-		level.Error(s.logger).Log("msg", "unable to parse JSON email", "err", err)
+		level.Error(s.logger).Log("msg", "unable to parse JSON email", "path", path, "err", err)
+		// if JSON parsing failed the `path` is renamed with an error suffix to avoid enqueued it again
+		newPath := fmt.Sprintf("%s%s", path, ErrorSuffix)
+		if err := os.Rename(path, newPath); err != nil {
+			level.Error(s.logger).Log("msg", "unable to rename bad JSON email path", "path", path, "newPath", newPath)
+			s.queue.Shutdown()
+		}
 		return true
 	}
 
+	// whatever the return, the email will be not enqueued again
 	s.SendMail(email)
 
 	if err := os.Remove(path); err != nil {
+		// this is a fatal error, can't send same e-mail indefinitely
+		if !os.IsExist(err) {
 			level.Error(s.logger).Log("msg", "unable to remove the JSON email", "path", path, "err", err)
+			s.queue.Shutdown()
+		}
 	}
 
 	return true
@@ -128,10 +143,14 @@ func (s Sender) Run() {
 	s.watchOutbox()
 	queueCh := s.run()
 
-	<-sigCh
+	select {
+	case <-sigCh:
 		s.logger.Log("msg", "stop signal received, stopping e-mail queue...")
 		s.queue.Shutdown()
+	case <-queueCh:
+		s.logger.Log("msg", "e-mail queue stopped successfully")
+
+	}
 
-	<-queueCh
 	s.logger.Log("msg", "sender service stopped successfully")
 }