/**
* 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.processor;
import org.apache.camel.Endpoint;
import org.apache.camel.Exchange;
import org.apache.camel.PollingConsumer;
import org.apache.camel.Processor;
import org.apache.camel.impl.LoggingExceptionHandler;
import org.apache.camel.impl.ServiceSupport;
import org.apache.camel.processor.resequencer.ResequencerEngine;
import org.apache.camel.processor.resequencer.SequenceElementComparator;
import org.apache.camel.processor.resequencer.SequenceSender;
import org.apache.camel.spi.ExceptionHandler;
import org.apache.camel.util.ServiceHelper;
/**
* A resequencer that re-orders a (continuous) stream of {@link Exchange}s. The
* algorithm implemented by {@link ResequencerEngine} is based on the detection
* of gaps in a message stream rather than on a fixed batch size. Gap detection
* in combination with timeouts removes the constraint of having to know the
* number of messages of a sequence (i.e. the batch size) in advance.
* <p>
* Messages must contain a unique sequence number for which a predecessor and a
* successor is known. For example a message with the sequence number 3 has a
* predecessor message with the sequence number 2 and a successor message with
* the sequence number 4. The message sequence 2,3,5 has a gap because the
* sucessor of 3 is missing. The resequencer therefore has to retain message 5
* until message 4 arrives (or a timeout occurs).
* <p>
* Instances of this class poll for {@link Exchange}s from a given
* <code>endpoint</code>. Resequencing work and the delivery of messages to
* the next <code>processor</code> is done within the single polling thread.
*
* @author Martin Krasser
*
* @version $Revision: 699788 $
*
* @see ResequencerEngine
*/
public class StreamResequencer extends ServiceSupport implements SequenceSender<Exchange>, Runnable, Processor {
private ExceptionHandler exceptionHandler;
private ResequencerEngine<Exchange> engine;
private PollingConsumer<? extends Exchange> consumer;
private Endpoint<? extends Exchange> endpoint;
private Processor processor;
private Thread worker;
private int capacity;
/**
* Creates a new {@link StreamResequencer} instance.
*
* @param endpoint
* endpoint to poll exchanges from.
* @param processor
* next processor that processes re-ordered exchanges.
* @param comparator
* a sequence element comparator for exchanges.
*/
public StreamResequencer(Endpoint<? extends Exchange> endpoint, Processor processor, SequenceElementComparator<Exchange> comparator) {
this.exceptionHandler = new LoggingExceptionHandler(getClass());
this.engine = new ResequencerEngine<Exchange>(comparator);
this.engine.setSequenceSender(this);
this.endpoint = endpoint;
this.processor = processor;
}
/**
* Returns this resequencer's exception handler.
*
* @return this resequencer's exception handler.
*/
public ExceptionHandler getExceptionHandler() {
return exceptionHandler;
}
/**
* Returns the next processor.
*
* @return the next processor.
*/
public Processor getProcessor() {
return processor;
}
/**
* Returns this resequencer's capacity. The capacity is the maximum number
* of exchanges that can be managed by this resequencer at a given point in
* time. If the capacity if reached, polling from the endpoint will be
* skipped for <code>timeout</code> milliseconds giving exchanges the
* possibility to time out and to be delivered after the waiting period.
*
* @return this resequencer's capacity.
*/
public int getCapacity() {
return capacity;
}
/**
* Returns this resequencer's timeout. This sets the resequencer engine's
* timeout via {@link ResequencerEngine#setTimeout(long)}. This value is
* also used to define the polling timeout from the endpoint.
*
* @return this resequencer's timeout.
* (Processor)
* @see ResequencerEngine#setTimeout(long)
*/
public long getTimeout() {
return engine.getTimeout();
}
public void setCapacity(int capacity) {
this.capacity = capacity;
}
public void setTimeout(long timeout) {
engine.setTimeout(timeout);
}
@Override
public String toString() {
return "StreamResequencer[to: " + processor + "]";
}
@Override
protected void doStart() throws Exception {
consumer = endpoint.createPollingConsumer();
ServiceHelper.startServices(processor, consumer);
worker = new Thread(this, this + " Polling Thread");
engine.start();
worker.start();
}
@Override
protected void doStop() throws Exception {
// let's stop everything in the reverse order
// no need to stop the worker thread -- it will stop automatically when this service is stopped
engine.stop();
ServiceHelper.stopServices(consumer, processor);
}
/**
* Sends the <code>exchange</code> to the next <code>processor</code>.
*
* @param o
* exchange to send.
*/
public void sendElement(Exchange o) throws Exception {
processor.process(o);
}
/**
* Loops over {@link #processExchange()}.
*/
public void run() {
while (!isStopped() && !isStopping()) {
try {
processExchange();
} catch (Exception e) {
exceptionHandler.handleException(e);
}
}
}
/**
* Processes an exchange received from the this resequencer's
* <code>endpoint</code>. Received exchanges are processed via
* {@link ResequencerEngine#insert(Object)}.
* {@link ResequencerEngine#deliver()} is then called in any case regardless
* whether a message was received or receiving timed out.
*
* @throws Exception
* if exchange delivery fails.
*/
protected void processExchange() throws Exception {
if (engine.size() >= capacity) {
Thread.sleep(getTimeout());
} else {
Exchange exchange = consumer.receive(getTimeout());
if (exchange != null) {
engine.insert(exchange);
}
}
engine.deliver();
}
public void process(Exchange exchange) throws Exception {
// empty since exchanges come from endpoint's polling consumer
}
}