service

README

service

service will install / un-install, start / stop, and run a program as a service (daemon). Currently supports Windows XP+, Linux/(systemd | Upstart | SysV), and OSX/Launchd.

Windows controls services by setting up callbacks that is non-trivial. This is very different then other systems. This package provides the same API despite the substantial differences. It also can be used to detect how a program is called, from an interactive terminal or from a service manager.

BUGS

• Dependencies field is not implemented for Linux systems and Launchd.
• OS X when running as a UserService Interactive will not be accurate.

Documentation

Overview

Package service provides a simple way to create a system service. Currently supports Windows, Linux/(systemd | Upstart | SysV), and OSX/Launchd.

Windows controls services by setting up callbacks that is non-trivial. This is very different then other systems. This package provides the same API despite the substantial differences. It also can be used to detect how a program is called, from an interactive terminal or from a service manager.

Examples in the example/ folder.

package main

import (
	"log"

	"github.com/k0sproject/service"
)

var logger service.Logger

type program struct{}

func (p *program) Start(s service.Service) error {
	// Start should not block. Do the actual work async.
	go p.run()
	return nil
}
func (p *program) run() {
	// Do work here
}
func (p *program) Stop(s service.Service) error {
	// Stop should not block. Return with a few seconds.
	return nil
}

func main() {
	svcConfig := &service.Config{
		Name:        "GoServiceTest",
		DisplayName: "Go Service Test",
		Description: "This is a test Go service.",
	}

	prg := &program{}
	s, err := service.New(prg, svcConfig)
	if err != nil {
		log.Fatal(err)
	}
	logger, err = s.Logger(nil)
	if err != nil {
		log.Fatal(err)
	}
	err = s.Run()
	if err != nil {
		logger.Error(err)
	}
}

Index

• Variables
• func ChooseSystem(a ...System)
• func Control(s Service, action string) error
• func Interactive() bool
• func Platform() string
• type Config
• type Interface
• type KeyValue
• type Logger
• type Service
  • func New(i Interface, c *Config) (Service, error)
• type Shutdowner
• type Status
• type System
  • func AvailableSystems() []System
  • func ChosenSystem() System

Variables

var (
	// ErrNameFieldRequired is returned when Config.Name is empty.
	ErrNameFieldRequired = errors.New("Config.Name field is required.")
	// ErrNoServiceSystemDetected is returned when no system was detected.
	ErrNoServiceSystemDetected = errors.New("No service system detected.")
	// ErrNotInstalled is returned when the service is not installed
	ErrNotInstalled = errors.New("the service is not installed")
)

var ConsoleLogger = consoleLogger{}

ConsoleLogger logs to the std err.

var ControlAction = [5]string{"start", "stop", "restart", "install", "uninstall"}

ControlAction list valid string texts to use in Control.

Functions

func ChooseSystem

func ChooseSystem(a ...System)

ChooseSystem chooses a system from the given system services. SystemServices are considered in the order they are suggested. Calling this may change what Interactive and Platform return.

func Control

func Control(s Service, action string) error

Control issues control functions to the service from a given action string.

func Interactive

func Interactive() bool

Interactive returns false if running under the OS service manager and true otherwise.

func Platform

func Platform() string

Platform returns a description of the system service.

Types

type Config

type Config struct {
	Name        string   // Required name of the service. No spaces suggested.
	DisplayName string   // Display name, spaces allowed.
	Description string   // Long description of service.
	UserName    string   // Run as username.
	Arguments   []string // Run with arguments.

	// Optional field to specify the executable for service.
	// If empty the current executable is used.
	Executable string

	// Array of service dependencies.
	// Not yet fully implemented on Linux or OS X:
	//  1. Support linux-systemd dependencies, just put each full line as the
	//     element of the string array, such as
	//     "After=network.target syslog.target"
	//     "Requires=syslog.target"
	//     Note, such lines will be directly appended into the [Unit] of
	//     the generated service config file, will not check their correctness.
	Dependencies []string

	// The following fields are not supported on Windows.
	WorkingDirectory string // Initial working directory.
	ChRoot           string

	Option KeyValue
}

Config provides the setup for a Service. The Name field is required.

type Interface

type Interface interface {
	// Start provides a place to initiate the service. The service doesn't
	// signal a completed start until after this function returns, so the
	// Start function must not take more then a few seconds at most.
	Start(s Service) error

	// Stop provides a place to clean up program execution before it is terminated.
	// It should not take more then a few seconds to execute.
	// Stop should not call os.Exit directly in the function.
	Stop(s Service) error
}

Interface represents the service interface for a program. Start runs before the hosting process is granted control and Stop runs when control is returned.

1. OS service manager executes user program.
2. User program sees it is executed from a service manager (IsInteractive is false).
3. User program calls Service.Run() which blocks.
4. Interface.Start() is called and quickly returns.
5. User program runs.
6. OS service manager signals the user program to stop.
7. Interface.Stop() is called and quickly returns. - For a successful exit, os.Exit should not be called in Interface.Stop().
8. Service.Run returns.
9. User program should quickly exit.

type KeyValue

type KeyValue map[string]interface{}

KeyValue provides a list of platform specific options. See platform docs for more details.

type Logger

type Logger interface {
	Error(v ...interface{}) error
	Warning(v ...interface{}) error
	Info(v ...interface{}) error

	Errorf(format string, a ...interface{}) error
	Warningf(format string, a ...interface{}) error
	Infof(format string, a ...interface{}) error
}

Logger writes to the system log.

type Service

type Service interface {
	// Run should be called shortly after the program entry point.
	// After Interface.Stop has finished running, Run will stop blocking.
	// After Run stops blocking, the program must exit shortly after.
	Run() error

	// Start signals to the OS service manager the given service should start.
	Start() error

	// Stop signals to the OS service manager the given service should stop.
	Stop() error

	// Restart signals to the OS service manager the given service should stop then start.
	Restart() error

	// Install setups up the given service in the OS service manager. This may require
	// greater rights. Will return an error if it is already installed.
	Install() error

	// Uninstall removes the given service from the OS service manager. This may require
	// greater rights. Will return an error if the service is not present.
	Uninstall() error

	// Opens and returns a system logger. If the user program is running
	// interactively rather then as a service, the returned logger will write to
	// os.Stderr. If errs is non-nil errors will be sent on errs as well as
	// returned from Logger's functions.
	Logger(errs chan<- error) (Logger, error)

	// SystemLogger opens and returns a system logger. If errs is non-nil errors
	// will be sent on errs as well as returned from Logger's functions.
	SystemLogger(errs chan<- error) (Logger, error)

	// String displays the name of the service. The display name if present,
	// otherwise the name.
	String() string

	// Platform displays the name of the system that manages the service.
	// In most cases this will be the same as service.Platform().
	Platform() string

	// Status returns the current service status.
	Status() (Status, error)
}

Service represents a service that can be run or controlled.

func New

func New(i Interface, c *Config) (Service, error)

New creates a new service based on a service interface and configuration.

type Shutdowner

type Shutdowner interface {
	Interface
	// Shutdown provides a place to clean up program execution when the system is being shutdown.
	// It is essentially the same as Stop but for the case where machine is being shutdown/restarted
	// instead of just normally stopping the service. Stop won't be called when Shutdown is.
	Shutdown(s Service) error
}

Shutdowner represents a service interface for a program that differentiates between "stop" and "shutdown". A shutdown is triggered when the whole box (not just the service) is stopped.

type Status

type Status byte

Status represents service status as an byte value

const (
	StatusUnknown Status = iota // Status is unable to be determined due to an error or it was not installed.
	StatusRunning
	StatusStopped
)

Status of service represented as an byte

type System

type System interface {
	// String returns a description of the system.
	String() string

	// Detect returns true if the system is available to use.
	Detect() bool

	// Interactive returns false if running under the system service manager
	// and true otherwise.
	Interactive() bool

	// New creates a new service for this system.
	New(i Interface, c *Config) (Service, error)
}

System represents the service manager that is available.

func AvailableSystems

func AvailableSystems() []System

AvailableSystems returns the list of system services considered when choosing the system service.

func ChosenSystem

func ChosenSystem() System

ChosenSystem returns the system that service will use.