#81: syslog handler

handlers/syslog/syslog.go

@@ -0,0 +1,74 @@
+// Package syslog implements output to local or remote hosts via the syslog protocol.
+package syslog
+
+import (
+	"fmt"
+	"log/syslog"
+
+	"github.com/apex/log"
+	"github.com/go-logfmt/logfmt"
+)
+
+// Handler implementation.
+type Handler struct {
+	log *syslog.Writer
+	// map apex levels to syslog levels.
+	levelsMap map[log.Level](func(m string) error)
+}
+
+// New syslog handler.
+//  addr: network address of syslog host. (default: localhost)
+//  facility: syslog facility, as defined in "log/syslog". (default: LOG_USER)
+//  tag: message identifier, usually the application name. (default: os.Args[0])
+func New(addr string, facility syslog.Priority, tag string) (h *Handler, err error) {
+	h = new(Handler)
+	if facility == 0 {
+		facility = syslog.LOG_USER
+	}
+
+	if addr == "" {
+		if h.log, err = syslog.New(facility, tag); err != nil {
+			// sometimes local socket connections don't work, so try localhost before
+			// giving up.
+			if h.log, err = syslog.Dial("tcp", "localhost:514", facility, tag); err != nil {
+				return nil, err
+			}
+		}
+	} else {
+		if h.log, err = syslog.Dial("tcp", addr, facility, tag); err != nil {
+			return nil, err
+		}
+	}
+
+	// create apex -> syslog level mapping dynamically with h.log methods.
+	// wish "log/syslog" had a Writer.Log(p Priority, m string) method.
+	h.levelsMap = map[log.Level](func(m string) error){
+		log.DebugLevel: h.log.Debug,
+		log.InfoLevel:  h.log.Info,
+		log.WarnLevel:  h.log.Warning,
+		log.ErrorLevel: h.log.Err,
+		log.FatalLevel: h.log.Emerg,
+	}
+
+	return h, nil
+}
+
+// HandleLog implements log.Handler.
+func (h *Handler) HandleLog(e *log.Entry) error {
+	keyvals := make([]interface{}, 0, len(e.Fields.Names()) * 2)
+	for _, name := range e.Fields.Names() {
+		if name == "source" {
+			continue
+		}
+		keyvals = append(keyvals, name)
+		keyvals = append(keyvals, e.Fields.Get(name))
+	}
+	fmt.Println("keyvals:", keyvals)
+
+	out, err := logfmt.MarshalKeyvals(keyvals...)
+	fmt.Println(string(out), err)
+	if err != nil {
+		return err
+	}
+	return h.levelsMap[e.Level](string(out))
+}