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184 lines
4.0 KiB
184 lines
4.0 KiB
/*
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Classical-inheritance-style service declarations.
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Services can be started, then stopped, then optionally restarted.
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Users can override the OnStart/OnStop methods.
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By default, these methods are guaranteed to be called at most once.
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A call to Reset will panic, unless OnReset is overwritten, allowing OnStart/OnStop to be called again.
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Caller must ensure that Start() and Stop() are not called concurrently.
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It is ok to call Stop() without calling Start() first.
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Services cannot be re-started unless OnReset is overwritten to allow it.
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Typical usage:
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type FooService struct {
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BaseService
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// private fields
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}
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func NewFooService() *FooService {
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fs := &FooService{
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// init
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}
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fs.BaseService = *NewBaseService(log, "FooService", fs)
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return fs
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}
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func (fs *FooService) OnStart() error {
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fs.BaseService.OnStart() // Always call the overridden method.
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// initialize private fields
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// start subroutines, etc.
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}
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func (fs *FooService) OnStop() error {
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fs.BaseService.OnStop() // Always call the overridden method.
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// close/destroy private fields
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// stop subroutines, etc.
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}
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*/
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package common
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import (
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"sync/atomic"
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"github.com/tendermint/log15"
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)
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type Service interface {
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Start() (bool, error)
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OnStart() error
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Stop() bool
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OnStop()
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Reset() (bool, error)
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OnReset() error
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IsRunning() bool
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String() string
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}
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type BaseService struct {
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log log15.Logger
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name string
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started uint32 // atomic
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stopped uint32 // atomic
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// The "subclass" of BaseService
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impl Service
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}
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func NewBaseService(log log15.Logger, name string, impl Service) *BaseService {
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return &BaseService{
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log: log,
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name: name,
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impl: impl,
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}
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}
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// Implements Servce
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func (bs *BaseService) Start() (bool, error) {
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if atomic.CompareAndSwapUint32(&bs.started, 0, 1) {
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if atomic.LoadUint32(&bs.stopped) == 1 {
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if bs.log != nil {
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bs.log.Warn(Fmt("Not starting %v -- already stopped", bs.name), "impl", bs.impl)
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}
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return false, nil
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} else {
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if bs.log != nil {
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bs.log.Info(Fmt("Starting %v", bs.name), "impl", bs.impl)
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}
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}
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err := bs.impl.OnStart()
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return true, err
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} else {
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if bs.log != nil {
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bs.log.Debug(Fmt("Not starting %v -- already started", bs.name), "impl", bs.impl)
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}
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return false, nil
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}
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}
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// Implements Service
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func (bs *BaseService) OnStart() error { return nil }
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// Implements Service
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func (bs *BaseService) Stop() bool {
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if atomic.CompareAndSwapUint32(&bs.stopped, 0, 1) {
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if bs.log != nil {
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bs.log.Info(Fmt("Stopping %v", bs.name), "impl", bs.impl)
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}
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bs.impl.OnStop()
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return true
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} else {
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if bs.log != nil {
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bs.log.Debug(Fmt("Stopping %v (ignoring: already stopped)", bs.name), "impl", bs.impl)
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}
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return false
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}
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}
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// Implements Service
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func (bs *BaseService) OnStop() {}
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// Implements Service
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func (bs *BaseService) Reset() (bool, error) {
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if atomic.CompareAndSwapUint32(&bs.stopped, 1, 0) {
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// whether or not we've started, we can reset
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atomic.CompareAndSwapUint32(&bs.started, 1, 0)
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return true, bs.impl.OnReset()
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} else {
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if bs.log != nil {
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bs.log.Debug(Fmt("Can't reset %v. Not stopped", bs.name), "impl", bs.impl)
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}
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return false, nil
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}
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// never happens
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return false, nil
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}
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// Implements Service
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func (bs *BaseService) OnReset() error {
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PanicSanity("The service cannot be reset")
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return nil
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}
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// Implements Service
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func (bs *BaseService) IsRunning() bool {
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return atomic.LoadUint32(&bs.started) == 1 && atomic.LoadUint32(&bs.stopped) == 0
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}
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// Implements Servce
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func (bs *BaseService) String() string {
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return bs.name
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}
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//----------------------------------------
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type QuitService struct {
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BaseService
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Quit chan struct{}
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}
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func NewQuitService(log log15.Logger, name string, impl Service) *QuitService {
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return &QuitService{
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BaseService: *NewBaseService(log, name, impl),
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Quit: nil,
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}
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}
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// NOTE: when overriding OnStart, must call .QuitService.OnStart().
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func (qs *QuitService) OnStart() error {
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qs.Quit = make(chan struct{})
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return nil
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}
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// NOTE: when overriding OnStop, must call .QuitService.OnStop().
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func (qs *QuitService) OnStop() {
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if qs.Quit != nil {
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close(qs.Quit)
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}
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}
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