[FEATURE] Made syslog integration OS specific

Windows doesn't have log/syslog package. Abstract syslog interface in OS specific
go files. Panic under Windows if syslog requested.

* Testing done:
* Bugs:
* Bugs closed:
* Severity: trivial|bugfix|feature
* Review URL: (recommended)
* Reviewed by: (recommended)
* Approved by:
* Commit template: 2014-01-07

glog.go

@@ -78,7 +78,6 @@ import (
 	"fmt"
 	"io"
 	stdLog "log"
-	"log/syslog"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -162,6 +161,11 @@ func severityByName(s string) (severity, bool) {
 	return 0, false
 }
 
+// internal interface for optional syslog facility
+type sysLogger interface {
+	log(s severity, msg string)
+}
+
 // OutputStats tracks the number of output lines and bytes written.
 type OutputStats struct {
 	lines int64
@@ -430,7 +434,7 @@ type loggingT struct {
 	stderrThreshold severity // The -stderrthreshold flag.
 
 	// syslog logger
-	sysLogger *syslog.Writer
+	sysLogger sysLogger
 
 	// freeList is a list of byte buffers, maintained under freeListMu.
 	freeList *buffer
@@ -683,7 +687,7 @@ func (l *loggingT) printWithFileLine(s severity, file string, line int, alsoToSt
 func (l *loggingT) output(s severity, buf *buffer, file string, line int, alsoToStderr bool) {
 	l.mu.Lock()
 	if l.toSyslog && l.sysLogger == nil {
-		sysLogger, err := syslog.Dial("", "", syslog.LOG_DEBUG, program)
+		sysLogger, err := NewSysLogger(program)
 		if err != nil {
 			l.mu.Unlock()
 			panic(err)
@@ -703,16 +707,7 @@ func (l *loggingT) output(s severity, buf *buffer, file string, line int, alsoTo
 	} else if l.toStderr {
 		os.Stderr.Write(data)
 	} else if l.toSyslog {
-		switch s {
-		case fatalLog:
-			l.sysLogger.Emerg(string(data))
-		case errorLog:
-			l.sysLogger.Err(string(data))
-		case warningLog:
-			l.sysLogger.Warning(string(data))
-		case infoLog:
-			l.sysLogger.Info(string(data))
-		}
+		l.sysLogger.log(s, string(data))
 	} else {
 		if alsoToStderr || l.alsoToStderr || s >= l.stderrThreshold.get() {
 			os.Stderr.Write(data)

glog_syslog_unix.go

@@ -0,0 +1,53 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2017 Nutanix Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Syslog IO for logs
+// +build linux darwin
+
+package glog
+
+import (
+	"log/syslog"
+)
+
+type unixSysLogger struct {
+	sysLogger *syslog.Writer
+}
+
+// implement sysLogger interface
+func (l *unixSysLogger) log(s severity, msg string) {
+	switch s {
+	case fatalLog:
+		l.sysLogger.Emerg(msg)
+	case errorLog:
+		l.sysLogger.Err(msg)
+	case warningLog:
+		l.sysLogger.Warning(msg)
+	case infoLog:
+		l.sysLogger.Info(msg)
+	}
+}
+
+func NewSysLogger(tag string) (sysLogger, error) {
+	sysLogger, err := syslog.Dial("", "", syslog.LOG_DEBUG, tag)
+	if err != nil {
+		return nil, err
+	} else {
+		return &unixSysLogger{
+			sysLogger: sysLogger,
+		}, nil
+	}
+}

glog_syslog_windows.go

@@ -0,0 +1,24 @@
+// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
+//
+// Copyright 2017 Nutanix Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Syslog IO for logs
+// +build windows
+
+package glog
+
+func NewSysLogger(tag string) (sysLogger, error) {
+	panic("Not implemented")
+}