logger

Package logger provides Logger4go which is a simple wrapper around go's log.Logger.

It provides three log handlers ConsoleHandler|FileHandler|SyslogHandler, wrapper methods named after syslog's severity levels and embedds log.Logger to provide seemless access to its methods as well if needed.

Supports:

- Write to multiple handlers, e.g., log to console, file and syslog at the same time.
- Use more than one logger instance. Each with its own set of handlers.
- Log file rotation (size or daily) and compression.
- Filter out severity levels.

Example output:

main 2013/06/21 08:21:44.680513 -info- init called
100m sprint 2013/06/21 08:21:44.680712 -info- Started 100m sprint: Should take 10 seconds.
Long jump 2013/06/21 08:21:44.680727 -info- Started Long jump: Should take 6 seconds.
High jump 2013/06/21 08:21:44.680748 -info- Started High jump: Should take 3 seconds.
High jump 2013/06/21 08:21:47.683402 -info- Finished High jump
Long jump 2013/06/21 08:21:50.683182 -info- Finished Long jump
100m sprint 2013/06/21 08:21:54.683871 -info- Finished 100m sprint
main 2013/06/21 08:22:14 -debug- A debug message
main 2013/06/21 08:22:14 -info- An info message
main 2013/06/21 08:22:14 -notice- A notice message
main 2013/06/21 08:22:14 -warn- A warning message
main 2013/06/21 08:22:14 -err- An error message
main 2013/06/21 08:22:14 -crit- A critical message
main 2013/06/21 08:22:14 -alert- An alert message
main 2013/06/21 08:22:14 -emerg- An emergency message

TODO: - Custom header format - Read settings from config file

package logger_test

import (
    "fmt"
    "github.com/alyu/logger"
    "log/syslog"
)

var lg *logger.Logger4go

func Example() {
    // get a new logger instance named "example" and with prefix example
    lg = logger.Get("example")
    lg.Info("This is not written out, we need to add a handler first")

    // log to console/stdout
    lg.AddConsoleHandler()
    lg.Info("This will be written out to stdout")

    // log to file. as default the log will be rotated 5 times with a
    // max filesize of 1MB starting with sequence no 1, daily rotate and compression disabled
    _, err := lg.AddStdFileHandler("/tmp/logger.log")
    if err != nil {
        fmt.Errorf("%v", err)
    }
    lg.Alert("This is an alert message written to the console and log file")

    // log to syslog
    protocol := "" // tcp|udp
    ipaddr := ""
    sh, err := lg.AddSyslogHandler(protocol, ipaddr, syslog.LOG_INFO|syslog.LOG_LOCAL0, "example")
    if err != nil {
        fmt.Errorf("%v", err)
    }
    lg.Notice("This is a critical message written to the console, log file and syslog")
    lg.Notice("The format written to syslog is the same as for the console and log file")
    err = sh.Out.Err("This is a message to syslog without any preformatted header, it just contains this message")
    if err != nil {
        fmt.Errorf("%v", err)
    }

    // filter logs
    lg.SetFilter(logger.DEBUG | logger.INFO)
    lg.Alert("This message should not be shown")
    lg.Debug("This debug message is filtered through")
    lg.Info("As well as this info message")

    lg = logger.GetWithFlags("micro", logger.Ldate|logger.Ltime|logger.Lmicroseconds)
    lg.Info("This is written out with micrseconds precision")

    // get standard logger
    log := logger.Std()
    log.Info("Standard logger always has a console handler")

    // add a file handler which rotates 5 files with a maximum size of 5MB starting with sequence no 1, daily midnight rotation disabled
    // and with compress logs enabled
    log.AddFileHandler("/tmp/logger2.log", uint(5*logger.MB), 5, 1, true, false)

    // add a file handler which keeps logs for 5 days with no filesize limit starting with sequence no 1, daily midnight rotation
    // and  compress logs enabled
    log.AddFileHandler("/tmp/logger3.log", 0, 5, 1, true, true)

    // add a file handler with only one daily midnight rotation and compress logs enabled
    log.AddFileHandler("/tmp/logger3.log", 0, 1, 1, true, true)

    // Same as above
    fh, _ := log.AddStdFileHandler("/tmp/logger4.log")
    fh.SetSize(0)
    fh.SetRotate(1)
    fh.SetCompress(true)
    fh.SetDaily(true)
}