Merge pull request #11 from mattkanwisher/master

Add structured logging to json and support for syslog

Author: fabxc

log/log.go

@@ -16,6 +16,8 @@ package log
 import (
 	"flag"
 	"fmt"
+	"net/url"
+	"os"
 	"runtime"
 	"strings"
 
@@ -39,10 +41,68 @@ func (f levelFlag) Set(level string) error {
 	return nil
 }
 
+func setSyslogFormatter(appname, facility string) error {
+	if appname == "" || facility == "" {
+		return fmt.Errorf("your missing a appname(%s) or local(%s)", appname, facility)
+	}
+
+	fmter, err := newSyslogger(appname, facility, origLogger.Formatter)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error creating syslog formatter: %v\n", err)
+		origLogger.Errorf("can't connect logger to syslog: %v", err)
+		return err
+	}
+	origLogger.Formatter = fmter
+	return nil
+}
+
+func setJSONFormatter() {
+	origLogger.Formatter = &logrus.JSONFormatter{}
+}
+
+type logFormatFlag struct{ uri string }
+
+// String implements flag.Value.
+func (f logFormatFlag) String() string {
+	return f.uri
+}
+
+// Set implements flag.Value.
+func (f logFormatFlag) Set(format string) error {
+	f.uri = format
+	u, err := url.Parse(format)
+	if err != nil {
+		return err
+	}
+	if u.Scheme != "logger" {
+		return fmt.Errorf("invalid scheme %s", u.Scheme)
+	}
+	jsonq := u.Query().Get("json")
+	if jsonq == "true" {
+		setJSONFormatter()
+	}
+
+	switch u.Opaque {
+	case "syslog":
+		appname := u.Query().Get("appname")
+		facility := u.Query().Get("local")
+		return setSyslogFormatter(appname, facility)
+	case "stdout":
+		origLogger.Out = os.Stdout
+	case "stderr":
+		origLogger.Out = os.Stderr
+
+	default:
+		return fmt.Errorf("unsupported logger %s", u.Opaque)
+	}
+	return nil
+}
+
 func init() {
-	// In order for this flag to take effect, the user of the package must call
+	// In order for these flags to take effect, the user of the package must call
 	// flag.Parse() before logging anything.
 	flag.Var(levelFlag{}, "log.level", "Only log messages with the given severity or above. Valid levels: [debug, info, warn, error, fatal].")
+	flag.Var(logFormatFlag{}, "log.format", "If set use a syslog logger or JSON logging. Example: logger:syslog?appname=bob&local=7 or logger:stdout?json=true. Defaults to stderr.")
 }
 
 type Logger interface {

log/syslog_formatter.go

@@ -0,0 +1,84 @@
+package log
+
+import (
+	"fmt"
+	"log/syslog"
+	"os"
+
+	"github.com/Sirupsen/logrus"
+)
+
+var ceeTag = []byte("@cee:")
+
+type syslogger struct {
+	wrap logrus.Formatter
+	out  *syslog.Writer
+}
+
+func newSyslogger(appname string, facility string, fmter logrus.Formatter) (*syslogger, error) {
+	priority, err := getFacility(facility)
+	if err != nil {
+		return nil, err
+	}
+	out, err := syslog.New(priority, appname)
+	return &syslogger{
+		out:  out,
+		wrap: fmter,
+	}, err
+}
+
+func getFacility(facility string) (syslog.Priority, error) {
+	switch facility {
+	case "0":
+		return syslog.LOG_LOCAL0, nil
+	case "1":
+		return syslog.LOG_LOCAL1, nil
+	case "2":
+		return syslog.LOG_LOCAL2, nil
+	case "3":
+		return syslog.LOG_LOCAL3, nil
+	case "4":
+		return syslog.LOG_LOCAL4, nil
+	case "5":
+		return syslog.LOG_LOCAL5, nil
+	case "6":
+		return syslog.LOG_LOCAL6, nil
+	case "7":
+		return syslog.LOG_LOCAL7, nil
+	}
+	return syslog.LOG_LOCAL0, fmt.Errorf("invalid local(%s) for syslog", facility)
+}
+
+func (s *syslogger) Format(e *logrus.Entry) ([]byte, error) {
+	data, err := s.wrap.Format(e)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "syslogger: can't format entry: %v\n", err)
+		return data, err
+	}
+	// only append tag to data sent to syslog (line), not to what
+	// is returned
+	line := string(append(ceeTag, data...))
+
+	switch e.Level {
+	case logrus.PanicLevel:
+		err = s.out.Crit(line)
+	case logrus.FatalLevel:
+		err = s.out.Crit(line)
+	case logrus.ErrorLevel:
+		err = s.out.Err(line)
+	case logrus.WarnLevel:
+		err = s.out.Warning(line)
+	case logrus.InfoLevel:
+		err = s.out.Info(line)
+	case logrus.DebugLevel:
+		err = s.out.Debug(line)
+	default:
+		err = s.out.Notice(line)
+	}
+
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "syslogger: can't send log to syslog: %v\n", err)
+	}
+
+	return data, err
+}