service: minor cleanup of comments (#8314)

libs/service/service.go

@@ -12,11 +12,8 @@ var (
 	// errAlreadyStopped is returned when somebody tries to stop an already
 	// stopped service (without resetting it).
 	errAlreadyStopped = errors.New("already stopped")
-)
 
-var (
 	_ Service = (*BaseService)(nil)
-	_ Service = (*NopService)(nil)
 )
 
 // Service defines a service that can be started, stopped, and reset.
@@ -75,8 +72,7 @@ Typical usage:
 	}
 
 	func (fs *FooService) OnStop() {
-		// close/destroy private fields
-		// stop subroutines, etc.
+		// close/destroy private fields and releases resources
 	}
 */
 type BaseService struct {
@@ -90,12 +86,6 @@ type BaseService struct {
 	impl Implementation
 }
 
-type NopService struct{}
-
-func (NopService) Start(_ context.Context) error { return nil }
-func (NopService) IsRunning() bool               { return true }
-func (NopService) Wait()                         {}
-
 // NewBaseService creates a new BaseService.
 func NewBaseService(logger log.Logger, name string, impl Implementation) *BaseService {
 	return &BaseService{
@@ -206,5 +196,5 @@ func (bs *BaseService) getWait() <-chan struct{} {
 // Wait blocks until the service is stopped.
 func (bs *BaseService) Wait() { <-bs.getWait() }
 
-// String implements Service by returning a string representation of the service.
+// String provides a human-friendly representation of the service.
 func (bs *BaseService) String() string { return bs.name }