Created
May 2, 2019 19:13
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SQS receiver using Project Reactor
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import com.amazonaws.services.sqs.AmazonSQS; | |
import com.amazonaws.services.sqs.model.AmazonSQSException; | |
import com.amazonaws.services.sqs.model.Message; | |
import com.amazonaws.services.sqs.model.ReceiveMessageRequest; | |
import org.slf4j.Logger; | |
import org.slf4j.LoggerFactory; | |
import reactor.core.publisher.Flux; | |
import reactor.core.publisher.FluxSink; | |
import reactor.core.scheduler.Schedulers; | |
import java.util.List; | |
import java.util.concurrent.locks.Condition; | |
import java.util.concurrent.locks.Lock; | |
import java.util.concurrent.locks.ReentrantLock; | |
public class ReactiveSqsListener { | |
private static final Logger logger = LoggerFactory.getLogger(ReactiveSqsListener.class); | |
public static Flux<Message> listen(AmazonSQS sqs, String responseQueueUrl) { | |
return Flux.<Message>create(sink -> { | |
Lock lock = new ReentrantLock(); | |
Condition demand = lock.newCondition(); | |
Runnable signal = () -> { | |
if (lock.tryLock()) { | |
demand.signal(); | |
lock.unlock(); | |
} | |
}; | |
sink.onRequest(l -> signal.run()) | |
.onDispose(signal::run); | |
ReceiveMessageRequest request = new ReceiveMessageRequest(responseQueueUrl) | |
.withWaitTimeSeconds(20); | |
lock.lock(); | |
try { | |
while (!sink.isCancelled()) { | |
if (sink.requestedFromDownstream() == 0) { | |
try { | |
demand.await(); | |
} catch (InterruptedException ignored) { | |
// we woke up! let's keep doing the things. | |
} | |
} | |
int maxNumberOfMessages = (int) Long.min(10, sink.requestedFromDownstream()); | |
if (maxNumberOfMessages < 1) { | |
continue; | |
} | |
//metrics - responseDemand.set(maxNumberOfMessages); | |
request.withMaxNumberOfMessages(maxNumberOfMessages); | |
List<Message> messages; | |
try { | |
messages = sqs.receiveMessage(request).getMessages(); | |
} catch (AmazonSQSException e) { | |
logger.warn("failed to execute request {}", request); | |
sink.error(e); | |
return; | |
} | |
//metrics - received.increment(messages.size()); | |
messages.forEach(sink::next); | |
} | |
} finally { | |
lock.unlock(); | |
} | |
}, FluxSink.OverflowStrategy.BUFFER) | |
.subscribeOn(Schedulers.elastic(), false) | |
} | |
} |
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