From 15d41395eb08a46f1f9755e17de49b55f44f1318 Mon Sep 17 00:00:00 2001
From: Jaime Soriano Pastor <jaime.soriano@elastic.co>
Date: Mon, 24 Sep 2018 22:52:31 +0200
Subject: [PATCH] Reduce errors on filebeat syslog stop (#8347) (#8377)

Fix a couple of errors seen when syslog input is stopped.

In case the input couldn't be started (e.g. port was already in use),
there was a nil pointer reference error when trying to stop it.

In any case, on stop, an error about use of closed connection was logged
lots of times.

(cherry picked from commit 9b270401833a56258bc1817eb373d7c07515a4cf)
---
 CHANGELOG.asciidoc                 |  2 ++
 filebeat/input/syslog/input.go     |  5 +++++
 filebeat/inputsource/udp/server.go | 12 ++++++++++--
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.asciidoc b/CHANGELOG.asciidoc
index ad84c8055247..16649a59a68b 100644
--- a/CHANGELOG.asciidoc
+++ b/CHANGELOG.asciidoc
@@ -33,6 +33,8 @@ https://github.com/elastic/beats/compare/v6.4.1...6.4[Check the HEAD diff]
 
 *Filebeat*
 
+- Fix some errors happening when stopping syslog input. {pull}8347[8347]
+
 *Heartbeat*
 
 *Metricbeat*
diff --git a/filebeat/input/syslog/input.go b/filebeat/input/syslog/input.go
index d8f7dde529a3..29b2325359fa 100644
--- a/filebeat/input/syslog/input.go
+++ b/filebeat/input/syslog/input.go
@@ -174,6 +174,7 @@ func (p *Input) Run() {
 		err := p.server.Start()
 		if err != nil {
 			p.log.Error("Error starting the server", "error", err)
+			return
 		}
 		p.started = true
 	}
@@ -185,6 +186,10 @@ func (p *Input) Stop() {
 	p.Lock()
 	defer p.Unlock()
 
+	if !p.started {
+		return
+	}
+
 	p.log.Info("Stopping Syslog input")
 	p.server.Stop()
 	p.started = false
diff --git a/filebeat/inputsource/udp/server.go b/filebeat/inputsource/udp/server.go
index 762e927a89bf..c263a2ca4e8a 100644
--- a/filebeat/inputsource/udp/server.go
+++ b/filebeat/inputsource/udp/server.go
@@ -96,7 +96,15 @@ func (u *Server) run() {
 				continue
 			}
 
-			u.log.Errorw("Error reading from the socket", "error", err)
+			// Closed network error string will never change in Go 1.X
+			// https://github.com/golang/go/issues/4373
+			opErr, ok := err.(*net.OpError)
+			if ok && strings.Contains(opErr.Err.Error(), "use of closed network connection") {
+				u.log.Info("Connection has been closed")
+				return
+			}
+
+			u.log.Errorf("Error reading from the socket %s", err)
 
 			// On Windows send the current buffer and mark it as truncated.
 			// The buffer will have content but length will return 0, addr will be nil.
@@ -115,8 +123,8 @@ func (u *Server) run() {
 // Stop stops the current udp server.
 func (u *Server) Stop() {
 	u.log.Info("Stopping UDP server")
-	u.Listener.Close()
 	close(u.done)
+	u.Listener.Close()
 	u.wg.Wait()
 	u.log.Info("UDP server stopped")
 }