From 28adcf0437e6f051b197655cf7c9ee4fceb3523a Mon Sep 17 00:00:00 2001
From: James Hillyerd <james@hillyerd.com>
Date: Mon, 29 Feb 2016 20:21:49 -0800
Subject: [PATCH] Graceful shutdown on error for httpd, smtpd, pop3d

---
 config/config.go  | 12 ++++++------
 httpd/server.go   | 16 +++++++++++++---
 pop3d/listener.go | 27 ++++++++++++++++++++-------
 smtpd/listener.go | 27 ++++++++++++++++++++-------
 4 files changed, 59 insertions(+), 23 deletions(-)

diff --git a/config/config.go b/config/config.go
index 2c648ec..9d1bdf1 100644
--- a/config/config.go
+++ b/config/config.go
@@ -193,11 +193,11 @@ func parseSMTPConfig() error {
 	}
 	addr := net.ParseIP(str)
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, str)
 	}
 	addr = addr.To4()
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, str)
 	}
 	smtpConfig.IP4address = addr
 
@@ -264,11 +264,11 @@ func parsePOP3Config() error {
 	}
 	addr := net.ParseIP(str)
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, str)
 	}
 	addr = addr.To4()
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, str)
 	}
 	pop3Config.IP4address = addr
 
@@ -307,11 +307,11 @@ func parseWebConfig() error {
 	}
 	addr := net.ParseIP(str)
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v'", section, option, str)
 	}
 	addr = addr.To4()
 	if addr == nil {
-		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, err)
+		return fmt.Errorf("Failed to parse [%v]%v: '%v' not IPv4!", section, option, str)
 	}
 	webConfig.IP4address = addr
 
diff --git a/httpd/server.go b/httpd/server.go
index b262b7f..afaa454 100644
--- a/httpd/server.go
+++ b/httpd/server.go
@@ -75,8 +75,8 @@ func Start() {
 	listener, err = net.Listen("tcp", addr)
 	if err != nil {
 		log.Errorf("HTTP failed to start TCP4 listener: %v", err)
-		// TODO More graceful early-shutdown procedure
-		panic(err)
+		emergencyShutdown()
+		return
 	}
 
 	// Listener go routine
@@ -104,7 +104,8 @@ func serve() {
 		// Nop
 	default:
 		log.Errorf("HTTP server failed: %v", err)
-		// TODO shutdown?
+		emergencyShutdown()
+		return
 	}
 }
 
@@ -141,3 +142,12 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		log.Errorf("HTTP failed to write response: %v", err)
 	}
 }
+
+func emergencyShutdown() {
+	// Shutdown Inbucket
+	select {
+	case _ = <-globalShutdown:
+	default:
+		close(globalShutdown)
+	}
+}
diff --git a/pop3d/listener.go b/pop3d/listener.go
index 3419e87..a245b65 100644
--- a/pop3d/listener.go
+++ b/pop3d/listener.go
@@ -47,16 +47,20 @@ func (s *Server) Start() {
 		cfg.IP4address, cfg.IP4port))
 	if err != nil {
 		log.Errorf("POP3 Failed to build tcp4 address: %v", err)
-		// TODO More graceful early-shutdown procedure
-		panic(err)
+		// serve() never called, so we do local shutdown here
+		close(s.localShutdown)
+		s.emergencyShutdown()
+		return
 	}
 
 	log.Infof("POP3 listening on TCP4 %v", addr)
 	s.listener, err = net.ListenTCP("tcp4", addr)
 	if err != nil {
 		log.Errorf("POP3 failed to start tcp4 listener: %v", err)
-		// TODO More graceful early-shutdown procedure
-		panic(err)
+		// serve() never called, so we do local shutdown here
+		close(s.localShutdown)
+		s.emergencyShutdown()
+		return
 	}
 
 	// Listener go routine
@@ -100,9 +104,9 @@ func (s *Server) serve() {
 					close(s.localShutdown)
 					return
 				default:
-					// TODO Implement a max error counter before shutdown?
-					// or maybe attempt to restart smtpd
-					panic(err)
+					close(s.localShutdown)
+					s.emergencyShutdown()
+					return
 				}
 			}
 		} else {
@@ -113,6 +117,15 @@ func (s *Server) serve() {
 	}
 }
 
+func (s *Server) emergencyShutdown() {
+	// Shutdown Inbucket
+	select {
+	case _ = <-s.globalShutdown:
+	default:
+		close(s.globalShutdown)
+	}
+}
+
 // Drain causes the caller to block until all active POP3 sessions have finished
 func (s *Server) Drain() {
 	// Wait for listener to exit
diff --git a/smtpd/listener.go b/smtpd/listener.go
index 5d63bd7..fe4286d 100644
--- a/smtpd/listener.go
+++ b/smtpd/listener.go
@@ -78,16 +78,20 @@ func (s *Server) Start() {
 		cfg.IP4address, cfg.IP4port))
 	if err != nil {
 		log.Errorf("Failed to build tcp4 address: %v", err)
-		// TODO More graceful early-shutdown procedure
-		panic(err)
+		// serve() never called, so we do local shutdown here
+		close(s.localShutdown)
+		s.emergencyShutdown()
+		return
 	}
 
 	log.Infof("SMTP listening on TCP4 %v", addr)
 	s.listener, err = net.ListenTCP("tcp4", addr)
 	if err != nil {
 		log.Errorf("SMTP failed to start tcp4 listener: %v", err)
-		// TODO More graceful early-shutdown procedure
-		panic(err)
+		// serve() never called, so we do local shutdown here
+		close(s.localShutdown)
+		s.emergencyShutdown()
+		return
 	}
 
 	if !s.storeMessages {
@@ -141,9 +145,9 @@ func (s *Server) serve() {
 					close(s.localShutdown)
 					return
 				default:
-					// TODO Implement a max error counter before shutdown?
-					// or maybe attempt to restart smtpd
-					panic(err)
+					close(s.localShutdown)
+					s.emergencyShutdown()
+					return
 				}
 			}
 		} else {
@@ -155,6 +159,15 @@ func (s *Server) serve() {
 	}
 }
 
+func (s *Server) emergencyShutdown() {
+	// Shutdown Inbucket
+	select {
+	case _ = <-s.globalShutdown:
+	default:
+		close(s.globalShutdown)
+	}
+}
+
 // Drain causes the caller to block until all active SMTP sessions have finished
 func (s *Server) Drain() {
 	// Wait for listener to exit