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[#72] Add ListenWithError method in Listener interface

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Listen and ListenWithError methods check if subscriber channel
has been closed. If so, ListenWithError passes error message
into provided channel.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>
This commit is contained in:
Alex Vanin 2020-10-13 18:37:38 +03:00 committed by Alex Vanin
parent ca006245d2
commit ccbb9ce6ab
1 changed files with 33 additions and 6 deletions
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39
pkg/morph/event/listener.go
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@ -17,10 +17,16 @@ type Listener interface {
// Must start the event listener.
//
// Must listen to events with the parser installed.
//
// Must return an error if event listening could not be started.
Listen(context.Context)
// Must start the event listener.
//
// Must listen to events with the parser installed.
//
// Must send error to channel if subscriber channel has been closed or
// it could not be started.
ListenWithError(context.Context, chan<- error)
// Must set the parser of particular contract event.
//
// Parser of each event must be set once. All parsers must be set before Listen call.
@ -78,7 +84,7 @@ var (
// Returns an error if listener was already started.
func (s listener) Listen(ctx context.Context) {
s.once.Do(func() {
if err := s.listen(ctx); err != nil {
if err := s.listen(ctx, nil); err != nil {
s.log.Error("could not start listen to events",
zap.String("error", err.Error()),
)
@ -86,7 +92,24 @@ func (s listener) Listen(ctx context.Context) {
})
}
func (s listener) listen(ctx context.Context) error {
// ListenWithError starts the listening for events with registered handlers and
// passing error message to intError channel if subscriber channel has been closed.
//
// Executes once, all subsequent calls do nothing.
//
// Returns an error if listener was already started.
func (s listener) ListenWithError(ctx context.Context, intError chan<- error) {
s.once.Do(func() {
if err := s.listen(ctx, intError); err != nil {
s.log.Error("could not start listen to events",
zap.String("error", err.Error()),
)
intError <- err
}
})
}
func (s listener) listen(ctx context.Context, intError chan<- error) error {
// create the list of listening contract hashes
hashes := make([]util.Uint160, 0)
@ -115,12 +138,12 @@ func (s listener) listen(ctx context.Context) error {
return err
}
s.listenLoop(ctx, chEvent)
s.listenLoop(ctx, chEvent, intError)
return nil
}
func (s listener) listenLoop(ctx context.Context, chEvent <-chan *result.NotificationEvent) {
func (s listener) listenLoop(ctx context.Context, chEvent <-chan *result.NotificationEvent, intErr chan<- error) {
loop:
for {
select {
@ -132,6 +155,10 @@ loop:
case notifyEvent, ok := <-chEvent:
if !ok {
s.log.Warn("stop event listener by channel")
if intErr != nil {
intErr <- errors.New("event subscriber connection has been terminated")
}
break loop
} else if notifyEvent == nil {
s.log.Warn("nil notification event was caught")