go-daemon

Library for writing system daemons in Go.

Now supported only UNIX-based OS (Windows is not supported). But the library was tested only on Linux and OSX, so that if you have an ability to test the library on other platforms, give me feedback, please (#26).

Please, feel free to send me bug reports and fixes. Many thanks to all contributors.

What is this fork for?

Unfortunately original library doesn't allow reborn from within child process. This feature can be used to restart the process from within itself. This small changes allow to perform something like this to restart daemon. Note the _GO_DAEMON=0 variable set to zero. This makes library follow parent control flow.

var cmd = exec.Command("bash", "-c", fmt.Sprintf("sleep 0.5s; _GO_DAEMON=0 %s start", appFilename()))
var err = cmd.Start()

The changes introduced in v0.1.6 tag branched from orginal v0.1.5.

Features

Goroutine-safe daemonization;
Out of box work with pid-files;
Easy handling of system signals;
The control of a daemon.

Installation

go get github.com/yell0w4x/go-daemon

You can use gopkg.in:

go get gopkg.in/yell0w4x/go-daemon.v0

If you want to use the library in production project, please use vendoring, because i can not ensure backward compatibility before release v1.0.

Examples

Documentation

godoc.org/github.com/sevlyar/go-daemon

How it works

We can not use fork syscall in Golang's runtime, because child process doesn't inherit threads and goroutines in that case. The library uses a simple trick: it runs its own copy with a mark - a predefined environment variable. Availability of the variable for the process means an execution in the child's copy. So that if the mark is not setted - the library executes parent's operations and runs its own copy with mark, and if the mark is setted - the library executes child's operations:

import "log"

func main() {
	Pre()

	context := new(Context)
	child, _ := context.Reborn()

	if child != nil {
		PostParent()
	} else {
		defer func() {
			if err := context.Release(); err != nil {
				log.Printf("Unable to release pid-file: %s", err.Error())
			}
		}()

		PostChild()
	}
}

yell0w4x / go-daemon