[common] revert started flag when service already stopped (#2326)

also, return ErrNotStarted when trying to stop a not-running service

libs/common/service.go

@@ -9,8 +9,15 @@ import (
 )
 
 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.
@@ -124,6 +131,8 @@ 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 -- already stopped", bs.name), "impl", bs.impl)
+			// revert flag
+			atomic.StoreUint32(&bs.started, 0)
 			return ErrAlreadyStopped
 		}
 		bs.Logger.Info(fmt.Sprintf("Starting %v", bs.name), "impl", bs.impl)
@@ -148,6 +157,12 @@ func (bs *BaseService) OnStart() error { return nil }
 // 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 -- have 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", bs.name), "impl", bs.impl)
 		bs.impl.OnStop()
 		close(bs.quit)