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Camel :: Disruptor component
/**
* 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.disruptor;
import java.util.HashSet;
import java.util.Set;
import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.Consumer;
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.ExceptionHandler;
import org.apache.camel.spi.ShutdownAware;
import org.apache.camel.spi.Synchronization;
import org.apache.camel.support.LoggingExceptionHandler;
import org.apache.camel.support.ServiceSupport;
import org.apache.camel.util.AsyncProcessorConverterHelper;
import org.apache.camel.util.ExchangeHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A Consumer for the Disruptor component.
*/
public class DisruptorConsumer extends ServiceSupport implements Consumer, Suspendable, ShutdownAware {
private static final Logger LOGGER = LoggerFactory.getLogger(DisruptorConsumer.class);
private static final AsyncCallback NOOP_ASYNC_CALLBACK = new AsyncCallback() {
@Override
public void done(boolean doneSync) {
//Noop
}
};
private final DisruptorEndpoint endpoint;
private final AsyncProcessor processor;
private ExceptionHandler exceptionHandler;
public DisruptorConsumer(final DisruptorEndpoint endpoint, final Processor processor) {
this.endpoint = endpoint;
this.processor = AsyncProcessorConverterHelper.convert(processor);
}
public ExceptionHandler getExceptionHandler() {
if (exceptionHandler == null) {
exceptionHandler = new LoggingExceptionHandler(endpoint.getCamelContext(), getClass());
}
return exceptionHandler;
}
public void setExceptionHandler(final ExceptionHandler exceptionHandler) {
this.exceptionHandler = exceptionHandler;
}
@Override
public DisruptorEndpoint getEndpoint() {
return endpoint;
}
@Override
protected void doStart() throws Exception {
getEndpoint().onStarted(this);
}
@Override
protected void doStop() throws Exception {
getEndpoint().onStopped(this);
}
@Override
protected void doSuspend() throws Exception {
getEndpoint().onStopped(this);
}
@Override
protected void doResume() throws Exception {
getEndpoint().onStarted(this);
}
Set createEventHandlers(final int concurrentConsumers) {
final Set eventHandlers = new HashSet();
for (int i = 0; i < concurrentConsumers; ++i) {
eventHandlers.add(new ConsumerEventHandler(i, concurrentConsumers));
}
return eventHandlers;
}
@Override
public boolean deferShutdown(final ShutdownRunningTask shutdownRunningTask) {
// deny stopping on shutdown as we want disruptor consumers to run in case some other queues
// depend on this consumer to run, so it can complete its exchanges
return true;
}
@Override
public void prepareShutdown(boolean suspendOnly, boolean forced) {
// nothing
}
@Override
public int getPendingExchangesSize() {
return getEndpoint().getDisruptor().getPendingExchangeCount();
}
@Override
public String toString() {
return "DisruptorConsumer[" + endpoint + "]";
}
private Exchange prepareExchange(final Exchange exchange) {
// send a new copied exchange with new camel context
// don't copy handovers as they are handled by the Disruptor Event Handlers
final Exchange newExchange = ExchangeHelper
.copyExchangeAndSetCamelContext(exchange, endpoint.getCamelContext(), false);
// set the from endpoint
newExchange.setFromEndpoint(endpoint);
return newExchange;
}
private void process(final SynchronizedExchange synchronizedExchange) {
try {
Exchange exchange = synchronizedExchange.getExchange();
final boolean ignore = exchange.hasProperties() && exchange
.getProperties().containsKey(DisruptorEndpoint.DISRUPTOR_IGNORE_EXCHANGE);
if (ignore) {
// Property was set and it was set to true, so don't process Exchange.
LOGGER.trace("Ignoring exchange {}", exchange);
return;
}
// send a new copied exchange with new camel context
final Exchange result = prepareExchange(exchange);
// We need to be notified when the exchange processing is complete to synchronize the original exchange
// This is however the last part of the processing of this exchange and as such can't be done
// in the AsyncCallback as that is called *AFTER* processing is considered to be done
// (see org.apache.camel.processor.CamelInternalProcessor.InternalCallback#done).
// To solve this problem, a new synchronization is set on the exchange that is to be
// processed
result.addOnCompletion(new Synchronization() {
@Override
public void onComplete(Exchange exchange) {
synchronizedExchange.consumed(result);
}
@Override
public void onFailure(Exchange exchange) {
synchronizedExchange.consumed(result);
}
});
// As the necessary post-processing of the exchange is done by the registered Synchronization,
// we can suffice with a no-op AsyncCallback
processor.process(result, NOOP_ASYNC_CALLBACK);
} catch (Exception e) {
Exchange exchange = synchronizedExchange.getExchange();
if (exchange != null) {
getExceptionHandler().handleException("Error processing exchange",
exchange, e);
} else {
getExceptionHandler().handleException(e);
}
}
}
/**
* Implementation of the {@link LifecycleAwareExchangeEventHandler} interface that passes all Exchanges to the
* {@link Processor} registered at this {@link DisruptorConsumer}.
*/
private class ConsumerEventHandler extends AbstractLifecycleAwareExchangeEventHandler {
private final int ordinal;
private final int concurrentConsumers;
ConsumerEventHandler(final int ordinal, final int concurrentConsumers) {
this.ordinal = ordinal;
this.concurrentConsumers = concurrentConsumers;
}
@Override
public void onEvent(final ExchangeEvent event, final long sequence, final boolean endOfBatch) throws Exception {
// Consumer threads are managed at the endpoint to achieve the optimal performance.
// However, both multiple consumers (pub-sub style multicasting) as well as 'worker-pool' consumers dividing
// exchanges amongst them are scheduled on their own threads and are provided with all exchanges.
// To prevent duplicate exchange processing by worker-pool event handlers, they are all given an ordinal,
// which can be used to determine whether he should process the exchange, or leave it for his brethren.
//see http://code.google.com/p/disruptor/wiki/FrequentlyAskedQuestions#How_do_you_arrange_a_Disruptor_with_multiple_consumers_so_that_e
if (sequence % concurrentConsumers == ordinal) {
process(event.getSynchronizedExchange());
}
}
}
}