Feature #1246 - Remote syslog (#1301)

* Remote syslog

* golint

* Initialize mutex

caddyhttp/httpserver/logger.go

@@ -0,0 +1,148 @@
+package httpserver
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/hashicorp/go-syslog"
+	"github.com/mholt/caddy"
+)
+
+var remoteSyslogPrefixes = map[string]string{
+	"syslog+tcp://": "tcp",
+	"syslog+udp://": "udp",
+	"syslog://":     "udp",
+}
+
+// Logger is shared between errors and log plugins and supports both logging to
+// a file (with an optional file roller), local and remote syslog servers.
+type Logger struct {
+	Output string
+	*log.Logger
+	Roller *LogRoller
+	writer io.Writer
+	fileMu *sync.RWMutex
+}
+
+// NewTestLogger creates logger suitable for testing purposes
+func NewTestLogger(buffer *bytes.Buffer) *Logger {
+	return &Logger{
+		Logger: log.New(buffer, "", 0),
+		fileMu: new(sync.RWMutex),
+	}
+}
+
+// Println wraps underlying logger with mutex
+func (l Logger) Println(args ...interface{}) {
+	l.fileMu.RLock()
+	l.Logger.Println(args...)
+	l.fileMu.RUnlock()
+}
+
+// Printf wraps underlying logger with mutex
+func (l Logger) Printf(format string, args ...interface{}) {
+	l.fileMu.RLock()
+	l.Logger.Printf(format, args...)
+	l.fileMu.RUnlock()
+}
+
+// Attach binds logger Start and Close functions to
+// controller's OnStartup and OnShutdown hooks.
+func (l *Logger) Attach(controller *caddy.Controller) {
+	if controller != nil {
+		// Opens file or connect to local/remote syslog
+		controller.OnStartup(l.Start)
+
+		// Closes file or disconnects from local/remote syslog
+		controller.OnShutdown(l.Close)
+	}
+}
+
+type syslogAddress struct {
+	network string
+	address string
+}
+
+func parseSyslogAddress(location string) *syslogAddress {
+	for prefix, network := range remoteSyslogPrefixes {
+		if strings.HasPrefix(location, prefix) {
+			return &syslogAddress{
+				network: network,
+				address: strings.TrimPrefix(location, prefix),
+			}
+		}
+	}
+
+	return nil
+}
+
+// Start initializes logger opening files or local/remote syslog connections
+func (l *Logger) Start() error {
+	// initialize mutex on start
+	l.fileMu = new(sync.RWMutex)
+
+	var err error
+
+selectwriter:
+	switch l.Output {
+	case "", "stderr":
+		l.writer = os.Stderr
+
+	case "stdout":
+		l.writer = os.Stdout
+
+	case "syslog":
+		l.writer, err = gsyslog.NewLogger(gsyslog.LOG_ERR, "LOCAL0", "caddy")
+		if err != nil {
+			return err
+		}
+	default:
+
+		if address := parseSyslogAddress(l.Output); address != nil {
+			l.writer, err = gsyslog.DialLogger(address.network, address.address, gsyslog.LOG_ERR, "LOCAL0", "caddy")
+
+			if err != nil {
+				return err
+			}
+
+			break selectwriter
+		}
+
+		var file *os.File
+
+		file, err = os.OpenFile(l.Output, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
+		if err != nil {
+			return err
+		}
+
+		if l.Roller != nil {
+			file.Close()
+			l.Roller.Filename = l.Output
+			l.writer = l.Roller.GetLogWriter()
+		} else {
+			l.writer = file
+		}
+	}
+
+	l.Logger = log.New(l.writer, "", 0)
+
+	return nil
+
+}
+
+// Close closes open log files or connections to syslog.
+func (l *Logger) Close() error {
+	// Will close local/remote syslog connections too :)
+	if closer, ok := l.writer.(io.WriteCloser); ok {
+		l.fileMu.Lock()
+		err := closer.Close()
+		l.fileMu.Unlock()
+		return err
+	}
+
+	return nil
+}