csimplestring / go-log

Go logging library

go-log

A simple logging library for Go, with powerful file handling and syslog support.

Examples

Default

This example uses the default log to write messages to standard out:

package main

import (
	"github.com/yieldr/go-log/log"
)

func main() {
	log.Info("Hello World.")
	log.Error("There's nothing more to this program.")
}

Using Sinks and Formats

package main

import (
	"github.com/yieldr/go-log/log"
	"os"
)

func main() {
	l := log.NewSimple(
		log.WriterSink(os.Stderr,
			"%s: %s[%d] %s\n",
			[]string{"priority", "executable", "pid", "message"}))
	l.Info("Here's a differently formatted log message.")
}

File Sink

This example buffers log messages in memory and writes the contents on disk every 30 seconds. Additionally the file handle is closed and reopened every hour, to release any resources held by the os. In addition to functions supported by Sink, this sink also allows the user to Flush(), Reload(), Close() and Write(b []byte).

package main

import (
	"github.com/yieldr/go-log/log"
	"os"
)

func main() {
	sink, err := log.FileSink("/var/log/app.log", log.BasicFormat, log.BasicFields)
	if err != nil {
		panic(err)
	}
	defer sink.Close()
	logger := log.NewSimple(sink)
	logger.Info("This will be buffered and eventually written to file.")
}

Syslog Sink

This example logs messages to the systems log daemon.

package main

import (
	"github.com/yieldr/go-log/log"
	"os"
)

func main() {
	syslog, err := log.SyslogSink(log.PriDebug, log.BasicFormat, log.BasicFields)
	if err != nil {
		panic(err)
	}
	logger := log.NewSimple(syslog)
	logger.Info("This will be logged to syslog")
}

Fields

The following fields are available for use in all sinks:

"prefix"       string              // static field available to all sinks
"seq"          uint64              // auto-incrementing sequence number
"start_time"   time.Time           // start time of the log
"time"         string              // formatted time of log entry
"full_time"    time.Time           // time of log entry
"rtime"        time.Duration       // relative time of log entry since started
"pid"          int                 // process id
"executable"   string              // executable filename

In addition, if verbose=true is passed to New(), the following (somewhat expensive) runtime fields are also available:

"funcname"     string              // function name where the log function was called
"lineno"       int                 // line number where the log function was called
"pathname"     string              // full pathname of caller
"filename"     string              // filename of caller

Logging functions

All these functions can also be called directly to use the default log.

func (*Logger) Log(priority Priority, v ...interface)
func (*Logger) Logf(priority Priority, format string, v ...interface{})
func (*Logger) Emergency(v ...interface)
func (*Logger) Emergencyf(format string, v ...interface{})
func (*Logger) Alert(v ...interface)
func (*Logger) Alertf(format string, v ...interface{})
func (*Logger) Critical(v ...interface)
func (*Logger) Criticalf(format string, v ...interface{})
func (*Logger) Error(v ...interface)
func (*Logger) Errorf(format string, v ...interface{})
func (*Logger) Warning(v ...interface)
func (*Logger) Warningf(format string, v ...interface{})
func (*Logger) Notice(v ...interface)
func (*Logger) Noticef(format string, v ...interface{})
func (*Logger) Info(v ...interface)
func (*Logger) Infof(format string, v ...interface{})
func (*Logger) Debug(v ...interface)
func (*Logger) Debugf(format string, v ...interface{})

Acknowledgements

This package is a fork of coreos/go-log, which in turn is inspired by ccding/go-logging.