service

Documentation

Overview

Package service may be internalized (made private) in future releases. XXX Deprecated.

Index

• Variables
• type BaseService
  • func NewBaseService(logger log.Logger, name string, impl Service) *BaseService
  • func (bs *BaseService) IsRunning() bool
  • func (*BaseService) OnReset() error
  • func (*BaseService) OnStart() error
  • func (*BaseService) OnStop()
  • func (bs *BaseService) Quit() <-chan struct{}
  • func (bs *BaseService) Reset() error
  • func (bs *BaseService) SetLogger(l log.Logger)
  • func (bs *BaseService) Start() error
  • func (bs *BaseService) Stop() error
  • func (bs *BaseService) String() string
  • func (bs *BaseService) Wait()
• type Service

Variables

var (
	// ErrAlreadyStarted is returned when somebody tries to start an already
	// running service.
	ErrAlreadyStarted = errors.New("already started")
	// ErrAlreadyStopped is returned when somebody tries to stop an already
	// stopped service (without resetting it).
	ErrAlreadyStopped = errors.New("already stopped")
	// ErrNotStarted is returned when somebody tries to stop a not running
	// service.
	ErrNotStarted = errors.New("not started")
)

Types

type BaseService

type BaseService struct {
	Logger log.Logger
	// contains filtered or unexported fields
}

Classical-inheritance-style service declarations. Services can be started, then stopped, then optionally restarted.

Users can override the OnStart/OnStop methods. In the absence of errors, these methods are guaranteed to be called at most once. If OnStart returns an error, service won't be marked as started, so the user can call Start again.

A call to Reset will panic, unless OnReset is overwritten, allowing OnStart/OnStop to be called again.

The caller must ensure that Start and Stop are not called concurrently.

It is ok to call Stop without calling Start first.

Typical usage:

type FooService struct {
	BaseService
	// private fields
}

func NewFooService() *FooService {
	fs := &FooService{
		// init
	}
	fs.BaseService = *NewBaseService(log, "FooService", fs)
	return fs
}

func (fs *FooService) OnStart() error {
	fs.BaseService.OnStart() // Always call the overridden method.
	// initialize private fields
	// start subroutines, etc.
}

func (fs *FooService) OnStop() error {
	fs.BaseService.OnStop() // Always call the overridden method.
	// close/destroy private fields
	// stop subroutines, etc.
}

func NewBaseService

func NewBaseService(logger log.Logger, name string, impl Service) *BaseService

NewBaseService creates a new BaseService.

func (*BaseService) IsRunning

func (bs *BaseService) IsRunning() bool

IsRunning implements Service by returning true or false depending on the service's state.

func (*BaseService) OnReset

func (*BaseService) OnReset() error

OnReset implements Service by panicking.

func (*BaseService) OnStart

func (*BaseService) OnStart() error

OnStart implements Service by doing nothing. NOTE: Do not put anything in here, that way users don't need to call BaseService.OnStart().

func (*BaseService) OnStop

func (*BaseService) OnStop()

OnStop implements Service by doing nothing. NOTE: Do not put anything in here, that way users don't need to call BaseService.OnStop().

func (*BaseService) Quit

func (bs *BaseService) Quit() <-chan struct{}

Quit Implements Service by returning a quit channel.

func (*BaseService) Reset

func (bs *BaseService) Reset() error

Reset implements Service by calling OnReset callback (if defined). An error will be returned if the service is running.

func (*BaseService) SetLogger

func (bs *BaseService) SetLogger(l log.Logger)

SetLogger implements Service by setting a logger.

func (*BaseService) Start

func (bs *BaseService) Start() error

Start implements Service by calling OnStart (if defined). An error will be returned if the service is already running or stopped. Not to start the stopped service, you need to call Reset.

func (*BaseService) Stop

func (bs *BaseService) Stop() error

Stop implements Service by calling OnStop (if defined) and closing quit channel. An error will be returned if the service is already stopped.

func (*BaseService) String

func (bs *BaseService) String() string

String implements Service by returning a string representation of the service.

func (*BaseService) Wait

func (bs *BaseService) Wait()

Wait blocks until the service is stopped.

type Service

type Service interface {
	// Start the service.
	// If it's already started or stopped, will return an error.
	// If OnStart() returns an error, it's returned by Start()
	Start() error
	OnStart() error

	// Stop the service.
	// If it's already stopped, will return an error.
	// OnStop must never error.
	Stop() error
	OnStop()

	// Reset the service.
	// Panics by default - must be overwritten to enable reset.
	Reset() error
	OnReset() error

	// Return true if the service is running
	IsRunning() bool

	// Quit returns a channel, which is closed once service is stopped.
	Quit() <-chan struct{}

	// String representation of the service
	String() string

	// SetLogger sets a logger.
	SetLogger(l log.Logger)
}

Service defines a service that can be started, stopped, and reset.