/**
* Attempts to receive a message using the given strategy. The method will continue to attempt to
* receive until either {@link ReceiveStrategy#isRetryable()} returns false, a message is
* received, or the consumer is stopped.
*
* @param strategy the strategy to use for receiving the message and determining retries
* @return the message or null if no message was received
*/
private HazelcastMQMessage doReceive(ReceiveStrategy strategy) {
HazelcastMQMessage msg = null;
do {
receiveLock.lock();
try {
IQueue<byte[]> queue = hazelcastMQContext.resolveQueue(destination);
if (queue == null && topicListener == null) {
throw new HazelcastMQException(
format("Destination cannot be resolved [%s].", destination));
} else if (queue == null) {
queue = topicListener.getQueue();
}
byte[] msgData = strategy.receive(queue);
if (msgData != null) {
msg = config.getMessageConverter().toMessage(msgData);
}
// Check for message expiration if we have a message with expiration
// time.
if (msg != null && msg.getHeaders().get(Headers.EXPIRATION) != null) {
long expirationTime = Long.parseLong(msg.getHeaders().get(Headers.EXPIRATION));
if (expirationTime != 0 && expirationTime <= System.currentTimeMillis()) {
log.info("Dropping message [{}] because it has expired.", msg.getId());
msg = null;
}
}
} finally {
receiveLock.unlock();
}
} while (msg == null && !closed && strategy.isRetryable());
return msg;
}
/**
* Stops message consumption (push or pull), removes any listeners from Hazelcast, and returns
* once all consuming threads have returned.
*/
void stop() {
if (!active) {
return;
}
receiveLock.lock();
try {
if (topicListener != null) {
topicListener.shutdown();
topicListener = null;
}
if (queueListener != null) {
queueListener.shutdown();
queueListener = null;
}
active = false;
receiveCondition.signalAll();
} finally {
receiveLock.unlock();
}
}