package common import ( "sync/atomic" "github.com/tendermint/tmlibs/log" ) type Service interface { Start() (bool, error) OnStart() error Stop() bool OnStop() Reset() (bool, error) OnReset() error IsRunning() bool String() string SetLogger(log.Logger) } /* 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 } 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, } } func (bs *BaseService) SetLogger(l log.Logger) { bs.Logger = l } // Implements Servce func (bs *BaseService) Start() (bool, error) { if atomic.CompareAndSwapUint32(&bs.started, 0, 1) { if atomic.LoadUint32(&bs.stopped) == 1 { bs.Logger.Error(Fmt("Not starting %v -- already stopped", bs.name), "impl", bs.impl) return false, nil } else { bs.Logger.Info(Fmt("Starting %v", bs.name), "impl", bs.impl) } err := bs.impl.OnStart() if err != nil { // revert flag atomic.StoreUint32(&bs.started, 0) return false, err } return true, err } else { bs.Logger.Debug(Fmt("Not starting %v -- already started", bs.name), "impl", bs.impl) return false, nil } } // Implements Service // NOTE: Do not put anything in here, // that way users don't need to call BaseService.OnStart() func (bs *BaseService) OnStart() error { return nil } // Implements Service func (bs *BaseService) Stop() bool { if atomic.CompareAndSwapUint32(&bs.stopped, 0, 1) { bs.Logger.Info(Fmt("Stopping %v", bs.name), "impl", bs.impl) bs.impl.OnStop() close(bs.Quit) return true } else { bs.Logger.Debug(Fmt("Stopping %v (ignoring: already stopped)", bs.name), "impl", bs.impl) return false } } // Implements Service // NOTE: Do not put anything in here, // that way users don't need to call BaseService.OnStop() func (bs *BaseService) OnStop() {} // Implements Service func (bs *BaseService) Reset() (bool, error) { if atomic.CompareAndSwapUint32(&bs.stopped, 1, 0) { // whether or not we've started, we can reset atomic.CompareAndSwapUint32(&bs.started, 1, 0) bs.Quit = make(chan struct{}) return true, bs.impl.OnReset() } else { bs.Logger.Debug(Fmt("Can't reset %v. Not stopped", bs.name), "impl", bs.impl) return false, nil } // never happens return false, nil } // Implements Service func (bs *BaseService) OnReset() error { PanicSanity("The service cannot be reset") return nil } // Implements Service func (bs *BaseService) IsRunning() bool { return atomic.LoadUint32(&bs.started) == 1 && atomic.LoadUint32(&bs.stopped) == 0 } func (bs *BaseService) Wait() { <-bs.Quit } // Implements Servce func (bs *BaseService) String() string { return bs.name } //---------------------------------------- type QuitService struct { BaseService } func NewQuitService(logger log.Logger, name string, impl Service) *QuitService { if logger != nil { logger.Info("QuitService is deprecated, use BaseService instead") } return &QuitService{ BaseService: *NewBaseService(logger, name, impl), } }