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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.camel.component.seda;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.ShutdownRunningTask;
import org.apache.camel.Suspendable;
import org.apache.camel.spi.ShutdownAware;
import org.apache.camel.spi.Synchronization;
import org.apache.camel.support.DefaultConsumer;
import org.apache.camel.support.UnitOfWorkHelper;
import org.apache.camel.util.ObjectHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A Consumer for the SEDA component.
*
* In this implementation there is a little slack period when you suspend/stop the consumer, by which the
* consumer may pickup a newly arrived messages and process it. That period is up till 1 second.
*/
public class SedaConsumer extends DefaultConsumer implements Runnable, ShutdownAware, Suspendable {
private static final Logger LOG = LoggerFactory.getLogger(SedaConsumer.class);
private final AtomicInteger taskCount = new AtomicInteger();
private volatile CountDownLatch latch;
private volatile boolean shutdownPending;
private volatile boolean forceShutdown;
private ExecutorService executor;
private final int pollTimeout;
public SedaConsumer(SedaEndpoint endpoint, Processor processor) {
super(endpoint, processor);
this.pollTimeout = endpoint.getPollTimeout();
}
@Override
public SedaEndpoint getEndpoint() {
return (SedaEndpoint) super.getEndpoint();
}
@Override
public boolean deferShutdown(ShutdownRunningTask shutdownRunningTask) {
// deny stopping on shutdown as we want seda consumers to run in case some other queues
// depend on this consumer to run, so it can complete its exchanges
return true;
}
@Override
public int getPendingExchangesSize() {
// the route is shutting down, so either we should purge the queue,
// or return how many exchanges are still on the queue
if (getEndpoint().isPurgeWhenStopping()) {
getEndpoint().purgeQueue();
}
return getEndpoint().getQueue().size();
}
@Override
public void prepareShutdown(boolean suspendOnly, boolean forced) {
// if we are suspending then we want to keep the thread running but just not route the exchange
// this logic is only when we stop or shutdown the consumer
if (suspendOnly) {
LOG.debug("Skip preparing to shutdown as consumer is being suspended");
return;
}
// signal we want to shutdown
shutdownPending = true;
forceShutdown = forced;
if (latch != null) {
LOG.debug("Preparing to shutdown, waiting for {} consumer threads to complete.", latch.getCount());
// wait for all threads to end
try {
latch.await();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
@Override
public boolean isRunAllowed() {
// if we force shutdown then do not allow running anymore
if (forceShutdown) {
return false;
}
if (isSuspending() || isSuspended()) {
// allow to run even if we are suspended as we want to
// keep the thread task running
return true;
}
return super.isRunAllowed();
}
@Override
public void run() {
taskCount.incrementAndGet();
try {
doRun();
} finally {
taskCount.decrementAndGet();
latch.countDown();
LOG.debug("Ending this polling consumer thread, there are still {} consumer threads left.", latch.getCount());
}
}
protected void doRun() {
BlockingQueue queue = getEndpoint().getQueue();
// loop while we are allowed, or if we are stopping loop until the queue is empty
while (queue != null && isRunAllowed()) {
// do not poll during CamelContext is starting, as we should only poll when CamelContext is fully started
if (getEndpoint().getCamelContext().getStatus().isStarting()) {
LOG.trace("CamelContext is starting so skip polling");
try {
// sleep at most 1 sec
Thread.sleep(Math.min(pollTimeout, 1000));
} catch (InterruptedException e) {
LOG.debug("Sleep interrupted, are we stopping? {}", isStopping() || isStopped());
Thread.currentThread().interrupt();
}
continue;
}
// do not poll if we are suspended or starting again after resuming
if (isSuspending() || isSuspended() || isStarting()) {
if (shutdownPending && queue.isEmpty()) {
LOG.trace(
"Consumer is suspended and shutdown is pending, so this consumer thread is breaking out because the task queue is empty.");
// we want to shutdown so break out if there queue is empty
break;
} else {
LOG.trace("Consumer is suspended so skip polling");
try {
// sleep at most 1 sec
Thread.sleep(Math.min(pollTimeout, 1000));
} catch (InterruptedException e) {
LOG.debug("Sleep interrupted, are we stopping? {}", isStopping() || isStopped());
Thread.currentThread().interrupt();
}
continue;
}
}
Exchange exchange = null;
try {
// use the end user configured poll timeout
exchange = queue.poll(pollTimeout, TimeUnit.MILLISECONDS);
if (LOG.isTraceEnabled()) {
LOG.trace("Polled queue {} with timeout {} ms. -> {}", ObjectHelper.getIdentityHashCode(queue), pollTimeout,
exchange);
}
if (exchange != null) {
try {
final Exchange target = exchange;
// prepare the exchange before sending to consumer
prepareExchange(target);
// callback to be executed when sending to consumer and processing is done
AsyncCallback callback = doneSync -> {
// log exception if an exception occurred and was not handled
if (target.getException() != null) {
getExceptionHandler().handleException("Error processing exchange", target,
target.getException());
}
};
// process the exchange
sendToConsumers(target, callback);
} catch (Exception e) {
getExceptionHandler().handleException("Error processing exchange", exchange, e);
}
} else if (shutdownPending && queue.isEmpty()) {
LOG.trace("Shutdown is pending, so this consumer thread is breaking out because the task queue is empty.");
// we want to shutdown so break out if there queue is empty
break;
}
} catch (InterruptedException e) {
LOG.debug("Sleep interrupted, are we stopping? {}", isStopping() || isStopped());
Thread.currentThread().interrupt();
} catch (Exception e) {
if (exchange != null) {
getExceptionHandler().handleException("Error processing exchange", exchange, e);
} else {
getExceptionHandler().handleException(e);
}
}
}
}
/**
* Strategy to prepare exchange for being processed by this consumer
*
* @param exchange the exchange
*/
protected void prepareExchange(Exchange exchange) {
// this consumer grabbed the exchange so mark its from this route/endpoint
exchange.getExchangeExtension().setFromEndpoint(getEndpoint());
exchange.getExchangeExtension().setFromRouteId(getRouteId());
}
/**
* Send the given {@link Exchange} to the consumer(s).
*
* If multiple consumers then they will each receive a copy of the Exchange. A multicast processor will send the
* exchange in parallel to the multiple consumers.
*
* If there is only a single consumer then its dispatched directly to it using same thread.
*
* @param exchange the exchange
* @param callback exchange callback to continue routing
* @throws Exception can be thrown if processing of the exchange failed
*/
protected void sendToConsumers(final Exchange exchange, final AsyncCallback callback) throws Exception {
// validate multiple consumers has been enabled
int size = getEndpoint().getConsumers().size();
if (size > 1 && !getEndpoint().isMultipleConsumersSupported()) {
throw new IllegalStateException("Multiple consumers for the same endpoint is not allowed: " + getEndpoint());
}
// if there are multiple consumers then multicast to them
if (getEndpoint().isMultipleConsumersSupported()) {
if (LOG.isTraceEnabled()) {
LOG.trace("Multicasting to {} consumers for Exchange: {}", size, exchange);
}
// handover completions, as we need to done this when the multicast is done
final List completions = exchange.getExchangeExtension().handoverCompletions();
// use a multicast processor to process it
AsyncProcessor mp = getEndpoint().getConsumerMulticastProcessor();
ObjectHelper.notNull(mp, "ConsumerMulticastProcessor", this);
// and use the asynchronous routing engine to support it
mp.process(exchange, doneSync -> {
// done the uow on the completions
try {
UnitOfWorkHelper.doneSynchronizations(exchange, completions);
} finally {
callback.done(doneSync);
}
});
} else {
// use the regular processor and use the asynchronous routing engine to support it
getAsyncProcessor().process(exchange, callback);
}
}
@Override
protected void doStart() throws Exception {
super.doStart();
latch = new CountDownLatch(getEndpoint().getConcurrentConsumers());
shutdownPending = false;
forceShutdown = false;
setupTasks();
getEndpoint().onStarted(this);
}
@Override
protected void doSuspend() throws Exception {
getEndpoint().onStopped(this);
}
@Override
protected void doResume() throws Exception {
getEndpoint().onStarted(this);
}
@Override
protected void doStop() throws Exception {
// ensure queue is purged if we stop the consumer
if (getEndpoint().isPurgeWhenStopping()) {
getEndpoint().purgeQueue();
}
getEndpoint().onStopped(this);
shutdownExecutor();
super.doStop();
}
@Override
protected void doShutdown() throws Exception {
shutdownExecutor();
}
private void shutdownExecutor() {
if (executor != null) {
getEndpoint().getCamelContext().getExecutorServiceManager().shutdownNow(executor);
executor = null;
}
}
/**
* Setup the thread pool and ensures tasks gets executed (if needed)
*/
private void setupTasks() {
int poolSize = getEndpoint().getConcurrentConsumers();
// create thread pool if needed
if (executor == null) {
executor = getEndpoint().getCamelContext().getExecutorServiceManager().newFixedThreadPool(this,
getEndpoint().getEndpointUri(), poolSize);
}
// submit needed number of tasks
int tasks = poolSize - taskCount.get();
LOG.debug("Creating {} consumer tasks with poll timeout {} ms.", tasks, pollTimeout);
for (int i = 0; i < tasks; i++) {
executor.execute(this);
}
}
}
