daemon

Documentation

Overview

Package daemon 0.11.0 for use with Go (golang) services.

Package daemon provides primitives for daemonization of golang services. This package is not provide implementation of user daemon, accordingly must have root rights to install/remove service. In the current implementation is only supported Linux and Mac Os X daemon.

Example:

	// Example of a daemon with echo service
	package main

	import (
		"fmt"
		"log"
		"net"
		"os"
		"os/signal"
		"syscall"

		"github.com/takama/daemon"
	)

	const (

		// name of the service
		name        = "myservice"
		description = "My Echo Service"

		// port which daemon should be listen
		port = ":9977"
	)

  // dependencies that are NOT required by the service, but might be used
  // var dependencies = []string{"dummy.service"}

	var stdlog, errlog *log.Logger

	// Service has embedded daemon
	type Service struct {
		daemon.Daemon
	}

	// Manage by daemon commands or run the daemon
	func (service *Service) Manage() (string, error) {

		usage := "Usage: myservice install | remove | start | stop | status"

		// if received any kind of command, do it
		if len(os.Args) > 1 {
			command := os.Args[1]
			switch command {
			case "install":
				return service.Install()
			case "remove":
				return service.Remove()
			case "start":
				return service.Start()
			case "stop":
				return service.Stop()
			case "status":
				return service.Status()
			default:
				return usage, nil
			}
		}

		// Do something, call your goroutines, etc

		// Set up channel on which to send signal notifications.
		// We must use a buffered channel or risk missing the signal
		// if we're not ready to receive when the signal is sent.
		interrupt := make(chan os.Signal, 1)
		signal.Notify(interrupt, os.Interrupt, os.Kill, syscall.SIGTERM)

		// Set up listener for defined host and port
		listener, err := net.Listen("tcp", port)
		if err != nil {
			return "Possibly was a problem with the port binding", err
		}

		// set up channel on which to send accepted connections
		listen := make(chan net.Conn, 100)
		go acceptConnection(listener, listen)

		// loop work cycle with accept connections or interrupt
		// by system signal
		for {
			select {
			case conn := <-listen:
				go handleClient(conn)
			case killSignal := <-interrupt:
				stdlog.Println("Got signal:", killSignal)
				stdlog.Println("Stoping listening on ", listener.Addr())
				listener.Close()
				if killSignal == os.Interrupt {
					return "Daemon was interrupted by system signal", nil
				}
				return "Daemon was killed", nil
			}
		}

		// never happen, but need to complete code
		return usage, nil
	}

	// Accept a client connection and collect it in a channel
	func acceptConnection(listener net.Listener, listen chan<- net.Conn) {
		for {
			conn, err := listener.Accept()
			if err != nil {
				continue
			}
			listen <- conn
		}
	}

	func handleClient(client net.Conn) {
		for {
			buf := make([]byte, 4096)
			numbytes, err := client.Read(buf)
			if numbytes == 0 || err != nil {
				return
			}
			client.Write(buf[:numbytes])
		}
	}

	func init() {
		stdlog = log.New(os.Stdout, "", log.Ldate|log.Ltime)
		errlog = log.New(os.Stderr, "", log.Ldate|log.Ltime)
	}

	func main() {
		srv, err := daemon.New(name, description, dependencies...)
		if err != nil {
			errlog.Println("Error: ", err)
			os.Exit(1)
		}
		service := &Service{srv}
		status, err := service.Manage()
		if err != nil {
			errlog.Println(status, "\nError: ", err)
			os.Exit(1)
		}
		fmt.Println(status)
	}

Go daemon

Package daemon linux version

Index

• Variables
• func ExecPath() (string, error)
• type Daemon
  • func New(name, description string, dependencies ...string) (Daemon, error)
• type Executable

Variables

var (
	// ErrUnsupportedSystem appears if try to use service on system which is not supported by this release
	ErrUnsupportedSystem = errors.New("Unsupported system")

	// ErrRootPrivileges appears if run installation or deleting the service without root privileges
	ErrRootPrivileges = errors.New("You must have root user privileges. Possibly using 'sudo' command should help")

	// ErrAlreadyInstalled appears if service already installed on the system
	ErrAlreadyInstalled = errors.New("Service has already been installed")

	// ErrNotInstalled appears if try to delete service which was not been installed
	ErrNotInstalled = errors.New("Service is not installed")

	// ErrAlreadyRunning appears if try to start already running service
	ErrAlreadyRunning = errors.New("Service is already running")

	// ErrAlreadyStopped appears if try to stop already stopped service
	ErrAlreadyStopped = errors.New("Service has already been stopped")
)

Functions

func ExecPath

func ExecPath() (string, error)

ExecPath tries to get executable path

Types

type Daemon

type Daemon interface {

	// Install the service into the system
	Install(args ...string) (string, error)

	// Remove the service and all corresponding files from the system
	Remove() (string, error)

	// Start the service
	Start() (string, error)

	// Stop the service
	Stop() (string, error)

	// Status - check the service status
	Status() (string, error)

	// Run - run executable service
	Run(e Executable) (string, error)
}

Daemon interface has a standard set of methods/commands

func New

func New(name, description string, dependencies ...string) (Daemon, error)

New - Create a new daemon

name: name of the service

description: any explanation, what is the service, its purpose

type Executable

type Executable interface {
	// Start - non-blocking start service
	Start()
	// Stop - non-blocking stop service
	Stop()
	// Run - blocking run service
	Run()
}

Executable interface defines controlling methods of executable service