You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
224 lines
6.2 KiB
224 lines
6.2 KiB
package service
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"sync/atomic"
|
|
|
|
"github.com/tendermint/tendermint/libs/log"
|
|
)
|
|
|
|
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")
|
|
)
|
|
|
|
// Service defines a service that can be started, stopped, and reset.
|
|
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(log.Logger)
|
|
|
|
// Wait blocks until the service is stopped.
|
|
Wait()
|
|
}
|
|
|
|
/*
|
|
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.
|
|
}
|
|
*/
|
|
type BaseService struct {
|
|
Logger log.Logger
|
|
name string
|
|
started uint32 // atomic
|
|
stopped uint32 // atomic
|
|
quit chan struct{}
|
|
|
|
// The "subclass" of BaseService
|
|
impl Service
|
|
}
|
|
|
|
// NewBaseService creates a new BaseService.
|
|
func NewBaseService(logger log.Logger, name string, impl Service) *BaseService {
|
|
if logger == nil {
|
|
logger = log.NewNopLogger()
|
|
}
|
|
|
|
return &BaseService{
|
|
Logger: logger,
|
|
name: name,
|
|
quit: make(chan struct{}),
|
|
impl: impl,
|
|
}
|
|
}
|
|
|
|
// SetLogger implements Service by setting a logger.
|
|
func (bs *BaseService) SetLogger(l log.Logger) {
|
|
bs.Logger = l
|
|
}
|
|
|
|
// 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 (bs *BaseService) Start() error {
|
|
if atomic.CompareAndSwapUint32(&bs.started, 0, 1) {
|
|
if atomic.LoadUint32(&bs.stopped) == 1 {
|
|
bs.Logger.Error(fmt.Sprintf("Not starting %v service -- already stopped", bs.name),
|
|
"impl", bs.impl)
|
|
// revert flag
|
|
atomic.StoreUint32(&bs.started, 0)
|
|
return ErrAlreadyStopped
|
|
}
|
|
bs.Logger.Info(fmt.Sprintf("Starting %v service", bs.name), "impl", bs.impl.String())
|
|
err := bs.impl.OnStart()
|
|
if err != nil {
|
|
// revert flag
|
|
atomic.StoreUint32(&bs.started, 0)
|
|
return err
|
|
}
|
|
return nil
|
|
}
|
|
bs.Logger.Debug(fmt.Sprintf("Not starting %v service -- already started", bs.name), "impl", bs.impl)
|
|
return ErrAlreadyStarted
|
|
}
|
|
|
|
// OnStart implements Service by doing nothing.
|
|
// NOTE: Do not put anything in here,
|
|
// that way users don't need to call BaseService.OnStart()
|
|
func (bs *BaseService) OnStart() error { return nil }
|
|
|
|
// Stop implements Service by calling OnStop (if defined) and closing quit
|
|
// channel. An error will be returned if the service is already stopped.
|
|
func (bs *BaseService) Stop() error {
|
|
if atomic.CompareAndSwapUint32(&bs.stopped, 0, 1) {
|
|
if atomic.LoadUint32(&bs.started) == 0 {
|
|
bs.Logger.Error(fmt.Sprintf("Not stopping %v service -- has not been started yet", bs.name),
|
|
"impl", bs.impl)
|
|
// revert flag
|
|
atomic.StoreUint32(&bs.stopped, 0)
|
|
return ErrNotStarted
|
|
}
|
|
bs.Logger.Info(fmt.Sprintf("Stopping %v service", bs.name), "impl", bs.impl)
|
|
bs.impl.OnStop()
|
|
close(bs.quit)
|
|
return nil
|
|
}
|
|
bs.Logger.Debug(fmt.Sprintf("Stopping %v service (already stopped)", bs.name), "impl", bs.impl)
|
|
return ErrAlreadyStopped
|
|
}
|
|
|
|
// OnStop implements Service by doing nothing.
|
|
// NOTE: Do not put anything in here,
|
|
// that way users don't need to call BaseService.OnStop()
|
|
func (bs *BaseService) OnStop() {}
|
|
|
|
// Reset implements Service by calling OnReset callback (if defined). An error
|
|
// will be returned if the service is running.
|
|
func (bs *BaseService) Reset() error {
|
|
if !atomic.CompareAndSwapUint32(&bs.stopped, 1, 0) {
|
|
bs.Logger.Debug(fmt.Sprintf("Can't reset %v service. Not stopped", bs.name), "impl", bs.impl)
|
|
return fmt.Errorf("can't reset running %s", bs.name)
|
|
}
|
|
|
|
// whether or not we've started, we can reset
|
|
atomic.CompareAndSwapUint32(&bs.started, 1, 0)
|
|
|
|
bs.quit = make(chan struct{})
|
|
return bs.impl.OnReset()
|
|
}
|
|
|
|
// OnReset implements Service by panicking.
|
|
func (bs *BaseService) OnReset() error {
|
|
panic("The service cannot be reset")
|
|
}
|
|
|
|
// IsRunning implements Service by returning true or false depending on the
|
|
// service's state.
|
|
func (bs *BaseService) IsRunning() bool {
|
|
return atomic.LoadUint32(&bs.started) == 1 && atomic.LoadUint32(&bs.stopped) == 0
|
|
}
|
|
|
|
// Wait blocks until the service is stopped.
|
|
func (bs *BaseService) Wait() {
|
|
<-bs.quit
|
|
}
|
|
|
|
// String implements Service by returning a string representation of the service.
|
|
func (bs *BaseService) String() string {
|
|
return bs.name
|
|
}
|
|
|
|
// Quit Implements Service by returning a quit channel.
|
|
func (bs *BaseService) Quit() <-chan struct{} {
|
|
return bs.quit
|
|
}
|