Review changes:

* Don't export LogWriterInterface. * newLogWriter(): Ensure that all objects share a single syslog connection. 

2 files changed, 40 insertions, 10 deletions

diff --git a/logger/logger.go b/logger/logger.go
index 6e238fb93c..0900f1f15f 100644
--- a/logger/logger.go
+++ b/logger/logger.go
@@ -5,6 +5,7 @@ import (
	"log/syslog"
	"runtime/debug"
	"strings"
+	"sync"
	"time"
 
	"github.com/juju/loggo"
@@ -13,9 +14,9 @@ import (
 // Name used in the prefix for all logged messages
 const LoggerName = "snappy"
 
-// LogWriterInterface allows the tests to replace the syslog
+// logWriterInterface allows the tests to replace the syslog
 // implementation.
-type LogWriterInterface interface {
+type logWriterInterface interface {
	// syslog.Writer
	Debug(m string) error
	Info(m string) error
@@ -26,9 +27,15 @@ type LogWriterInterface interface {
 
 // LogWriter object that handles writing log entries
 type LogWriter struct {
-	systemLog LogWriterInterface
+	systemLog logWriterInterface
 }
 
+// Used to ensure that only a single connection to syslog is created
+var once sync.Once
+
+// A single connection to the system logger
+var syslogConnection logWriterInterface
+
 // Write sends the log details specified by the params to the logging
 // back-end (in this case syslog).
 func (l *LogWriter) Write(level loggo.Level, name string, filename string, line int, timestamp time.Time, message string) {
@@ -91,22 +98,29 @@ func (l *LogWriter) Format(level loggo.Level, module, filename string, line int,
 }
 
 // A variable to make testing easier
-var getSyslog = func(priority syslog.Priority, tag string) (w LogWriterInterface, err error) {
+var getSyslog = func(priority syslog.Priority, tag string) (w logWriterInterface, err error) {
	return syslog.New(syslog.LOG_NOTICE|syslog.LOG_LOCAL0, LoggerName)
 }
 
-// newLogWriter creates a new LogWriter.
+// newLogWriter creates a new LogWriter, ensuring that only a single
+// connection to the system logger is created.
 func newLogWriter() (l *LogWriter, err error) {
 
	l = new(LogWriter)
 
-	// Note that the log level here is just the default - Write()
-	// will alter it as needed.
-	l.systemLog, err = getSyslog(syslog.LOG_NOTICE|syslog.LOG_LOCAL0, LoggerName)
+	once.Do(func() {
+
+	// Note that the log level here is just the default - Write()
+	// will alter it as needed.
+	syslogConnection, err = getSyslog(syslog.LOG_NOTICE|syslog.LOG_LOCAL0, LoggerName)
+	})
+
	if err != nil {
	return nil, err
	}
 
+	l.systemLog = syslogConnection
+
	return l, nil
 }
 
diff --git a/logger/logger_test.go b/logger/logger_test.go
index db5ed1cee9..45beb5d2db 100644
--- a/logger/logger_test.go
+++ b/logger/logger_test.go
@@ -27,7 +27,7 @@ type MockLogWriter struct {
 
 var mockWriter *MockLogWriter
 
-func mockGetSyslog(priority syslog.Priority, tag string) (w LogWriterInterface, err error) {
+func mockGetSyslog(priority syslog.Priority, tag string) (w logWriterInterface, err error) {
	mockWriter = &MockLogWriter{}
	return mockWriter, nil
 }
@@ -41,6 +41,8 @@ func readLines() (lines []string) {
	if last == "" {
	lines = lines[:length-1]
	}
+	// clear the buffer to avoid contents accumulating indefinitely
+	mockWriter.buf.Reset()
	return lines
 }
 
@@ -92,10 +94,23 @@ func sliceContainsRegex(array []string, regex string) bool {
 }
 
 func (ts *LoggerTestSuite) TestNewLogWriter(c *C) {
-	w, err := newLogWriter()
+	var w, w2 *LogWriter
+	var err error
+
+	w, err = newLogWriter()
	c.Assert(err, IsNil)
	c.Assert(w, Not(IsNil))
	c.Assert(w.systemLog, Not(IsNil))
+
+	w2, err = newLogWriter()
+	c.Assert(err, IsNil)
+	c.Assert(w2, Not(IsNil))
+	c.Assert(w2.systemLog, Not(IsNil))
+
+	// There should be a single shared syslog connection, hence the
+	// systemLog objects should be identical.
+	c.Assert(w.systemLog, Equals, w2.systemLog)
+	c.Assert(w.systemLog, DeepEquals, w2.systemLog)
 }
 
 func (ts *LoggerTestSuite) TestWrite(c *C) {
@@ -190,6 +205,7 @@ func (ts *LoggerTestSuite) checkLogLevel(c *C, level, msg string) {
 
	lines := readLines()
 
+
	if expectBacktrace {
	c.Assert(len(lines) > 1, Equals, true)
	} else {