Method watchDNSLoop

pkg/util/dns_watcher.go:49–83

watchDNSLoop watches for changes in DNS and sends notifications.

(servCtx context.Context)

// watchDNSLoop watches for changes in DNS and sends notifications.
func (w *dnsWatcher) watchDNSLoop(servCtx context.Context) error {
	go func() {
		// Close the watcher, when this service is asked to stop.
		// Closing the watcher makes watchDNSLoop exit, since it only iterates on watcher updates, and has no other
		// way to stop. We cannot close the watcher in `stopping` method, because it is only called *after*
		// watchDNSLoop exits.
		<-servCtx.Done()
		w.watcher.Close()
	}()

	for {
		updates, err := w.watcher.Next()
		if err != nil {
			// watcher.Next returns error when Close is called, but we call Close when our context is done.
			// we don't want to report error in that case.
			if servCtx.Err() != nil {
				return nil
			}
			return errors.Wrapf(err, "error from DNS watcher")
		}

		for _, update := range updates {
			switch update.Op {
			case grpcutil.Add:
				w.notifications.AddressAdded(update.Addr)

			case grpcutil.Delete:
				w.notifications.AddressRemoved(update.Addr)

			default:
				return fmt.Errorf("unknown op: %v", update.Op)
			}
		}
	}
}