/** {@inheritDoc} */
@Override
public boolean sendMessageToSubscriber(ProtocolMessage protocolMessage, AndesContent content)
throws AndesException {
boolean sendSuccess;
DeliverableAndesMetadata messageMetadata = protocolMessage.getMessage();
if (messageMetadata.isRetain()) {
recordRetainedMessage(messageMetadata.getMessageID());
}
// Should get the message from the list
ByteBuffer message = MQTTUtils.getContentFromMetaInformation(content);
// Will publish the message to the respective queue
if (null != mqqtServerChannel) {
try {
// TODO:review - instead of getSubscribedDestination() used message destination
mqqtServerChannel.distributeMessageToSubscriber(
wildcardDestination,
message,
messageMetadata.getMessageID(),
messageMetadata.getQosLevel(),
messageMetadata.isPersistent(),
getMqttSubscriptionID(),
getSubscriberQOS(),
messageMetadata);
// We will indicate the ack to the kernel at this stage
// For MQTT QOS 0 we do not get ack from subscriber, hence will be implicitly creating an
// ack
if (QOSLevel.AT_MOST_ONCE.getValue() == getSubscriberQOS()
|| QOSLevel.AT_MOST_ONCE.getValue() == messageMetadata.getQosLevel()) {
mqqtServerChannel.implicitAck(messageMetadata.getMessageID(), getChannelID());
}
sendSuccess = true;
} catch (MQTTException e) {
final String error =
"Error occurred while delivering message to the subscriber for message :"
+ messageMetadata.getMessageID();
log.error(error, e);
throw new AndesException(error, e);
}
} else {
sendSuccess = false;
}
return sendSuccess;
}
/** {@inheritDoc} */
@Override
public int deliverMessageToSubscriptions(MessageDeliveryInfo messageDeliveryInfo)
throws AndesException {
Set<DeliverableAndesMetadata> messages = messageDeliveryInfo.getReadButUndeliveredMessages();
int sentMessageCount = 0;
Iterator<DeliverableAndesMetadata> iterator = messages.iterator();
List<DeliverableAndesMetadata> droppedTopicMessagesList = new ArrayList<>();
/**
* get all relevant type of subscriptions. This call does NOT return hierarchical subscriptions
* for the destination. There are duplicated messages for each different subscribed destination.
* For durable topic subscriptions this should return queue subscription bound to unique queue
* based on subscription id
*/
Collection<LocalSubscription> subscriptions =
subscriptionEngine.getActiveLocalSubscribers(
messageDeliveryInfo.getDestination(),
messageDeliveryInfo.getProtocolType(),
messageDeliveryInfo.getDestinationType());
while (iterator.hasNext()) {
try {
DeliverableAndesMetadata message = iterator.next();
// All subscription filtering logic for topics goes here
List<LocalSubscription> subscriptionsToDeliver = new ArrayList<>();
for (LocalSubscription subscription : subscriptions) {
/*
* If this is a topic message, remove all durable topic subscriptions here
* because durable topic subscriptions will get messages via queue path.
* Also need to consider the arrival time of the message. Only topic
* subscribers which appeared before publishing this message should receive it
*/
if (subscription.isDurable()
|| (subscription.getSubscribeTime() > message.getArrivalTime())) {
continue;
}
// Avoid sending if the selector of subscriber does not match
if (!subscription.isMessageAcceptedBySelector(message)) {
continue;
}
subscriptionsToDeliver.add(subscription);
}
if (subscriptionsToDeliver.size() == 0) {
iterator.remove(); // remove buffer
droppedTopicMessagesList.add(message);
continue; // skip this iteration if no subscriptions for the message
}
/**
* For normal non-durable topic we pre evaluate room for all subscribers and if all subs has
* room to accept messages we send them. This means we operate to the speed of slowest
* subscriber (to prevent OOM). If it is too slow to make others fast, make that topic
* subscriber a durable topic subscriber.
*/
boolean allTopicSubscriptionsHasRoom = true;
for (LocalSubscription subscription : subscriptionsToDeliver) {
if (!subscription.hasRoomToAcceptMessages()) {
allTopicSubscriptionsHasRoom = false;
break;
}
}
if (allTopicSubscriptionsHasRoom) {
message.markAsScheduledToDeliver(subscriptionsToDeliver);
// schedule message to all subscribers
for (LocalSubscription localSubscription : subscriptionsToDeliver) {
MessageFlusher.getInstance().deliverMessageAsynchronously(localSubscription, message);
}
iterator.remove();
if (log.isDebugEnabled()) {
log.debug(
"Removing Scheduled to send message from buffer. MsgId= " + message.getMessageID());
}
sentMessageCount++;
} else {
if (log.isDebugEnabled()) {
log.debug(
"Some subscriptions for destination "
+ messageDeliveryInfo.getDestination()
+ " have max unacked messages "
+ message.getDestination());
}
// if we continue message order will break
break;
}
} catch (NoSuchElementException ex) {
// This exception can occur because the iterator of ConcurrentSkipListSet loads the
// at-the-time snapshot.
// Some records could be deleted by the time the iterator reaches them.
// However, this can only happen at the tail of the collection, not in middle, and it would
// cause the loop
// to blindly check for a batch of deleted records.
// Given this situation, this loop should break so the sendFlusher can re-trigger it.
// for tracing purposes can use this : log.warn("NoSuchElementException thrown",ex);
log.warn("NoSuchElementException thrown. ", ex);
break;
}
}
/**
* Here we do not need to have orphaned slot scenario (return slot). If there are no subscribers
* slot will be consumed and metadata will be removed. We duplicate topic messages per node
*/
/**
* delete topic messages that were dropped due to no subscriptions for the message and due to
* has no room to enqueue the message. Delete call is blocking and then slot message count is
* dropped in order
*/
MessagingEngine.getInstance().deleteMessages(droppedTopicMessagesList);
return sentMessageCount;
}
