From 508ce2bcf32875c74f2d2304efcb34665a2632d0 Mon Sep 17 00:00:00 2001
From: Colin Sullivan <colin@synadia.com>
Date: Tue, 13 Mar 2018 19:08:45 -0600
Subject: [PATCH] implement io.Closer interface in the logger

---
 logger/log.go | 13 +++++++------
 server/log.go | 13 ++++++++-----
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/logger/log.go b/logger/log.go
index 260c1404..2a8b737f 100644
--- a/logger/log.go
+++ b/logger/log.go
@@ -78,14 +78,15 @@ func NewFileLogger(filename string, time, debug, trace, pid bool) *Logger {
 	return l
 }
 
-// Close cleans up any resources with the server's logger implementation.
-func (l *Logger) Close() {
-	if l.logFile != nil {
-		if err := l.logFile.Close(); err != nil {
-			l.Noticef("couldn't close log file on restart:  %v", err)
-		}
+// Close implements the io.Closer interface to clean up
+// resources in the server's logger implementation.
+// Caller must ensure threadsafety.
+func (l *Logger) Close() error {
+	if f := l.logFile; f != nil {
 		l.logFile = nil
+		return f.Close()
 	}
+	return nil
 }
 
 // Generate the pid prefix string
diff --git a/server/log.go b/server/log.go
index f6fb8564..5b816b04 100644
--- a/server/log.go
+++ b/server/log.go
@@ -3,6 +3,7 @@
 package server
 
 import (
+	"io"
 	"os"
 	"sync/atomic"
 
@@ -78,11 +79,13 @@ func (s *Server) SetLogger(logger Logger, debugFlag, traceFlag bool) {
 	}
 	s.logging.Lock()
 	if s.logging.logger != nil {
-		// if we are the server's logger, call its Close function, but check
-		// the type because this could be a logger from another process
-		// embedding the NATS server, a SysLogger, or a dummy test logger.
-		if l, ok := s.logging.logger.(*srvlog.Logger); ok {
-			l.Close()
+		// Check to see if the logger implements io.Closer.  This could be a
+		// logger from another process embedding the NATS server or a dummy
+		// test logger that may not implement that interface.
+		if l, ok := s.logging.logger.(io.Closer); ok {
+			if err := l.Close(); err != nil {
+				s.Noticef("error closing logger: %v", err)
+			}
 		}
 	}
 	s.logging.logger = logger