org.apache.camel.processor.StreamResequencer Maven / Gradle / Ivy
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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.processor;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.camel.AsyncCallback;
import org.apache.camel.CamelContext;
import org.apache.camel.CamelExchangeException;
import org.apache.camel.Exchange;
import org.apache.camel.Expression;
import org.apache.camel.Navigate;
import org.apache.camel.Processor;
import org.apache.camel.Traceable;
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.spi.IdAware;
import org.apache.camel.support.AsyncProcessorSupport;
import org.apache.camel.support.LoggingExceptionHandler;
import org.apache.camel.support.service.ServiceHelper;
import org.apache.camel.util.ObjectHelper;
/**
* 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.
*
* 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
* successor of 3 is missing. The resequencer therefore has to retain message 5
* until message 4 arrives (or a timeout occurs).
*
* Instances of this class poll for {@link Exchange}s from a given
* endpoint. Resequencing work and the delivery of messages to
* the next processor is done within the single polling thread.
*
*
* @see ResequencerEngine
*/
public class StreamResequencer extends AsyncProcessorSupport implements SequenceSender, Navigate, Traceable, IdAware {
private String id;
private final CamelContext camelContext;
private final ExceptionHandler exceptionHandler;
private final ResequencerEngine engine;
private final Processor processor;
private final Expression expression;
private Delivery delivery;
private int capacity;
private boolean ignoreInvalidExchanges;
private long deliveryAttemptInterval = 1000L;
/**
* Creates a new {@link StreamResequencer} instance.
*
* @param processor next processor that processes re-ordered exchanges.
* @param comparator a sequence element comparator for exchanges.
*/
public StreamResequencer(CamelContext camelContext, Processor processor, SequenceElementComparator comparator, Expression expression) {
ObjectHelper.notNull(camelContext, "CamelContext");
this.camelContext = camelContext;
this.engine = new ResequencerEngine<>(comparator);
this.engine.setSequenceSender(this);
this.processor = processor;
this.expression = expression;
this.exceptionHandler = new LoggingExceptionHandler(camelContext, getClass());
}
public Expression getExpression() {
return expression;
}
/**
* Returns this resequencer's exception handler.
*/
public ExceptionHandler getExceptionHandler() {
return exceptionHandler;
}
/**
* Returns 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 timeout 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);
}
public void setDeliveryAttemptInterval(long deliveryAttemptInterval) {
this.deliveryAttemptInterval = deliveryAttemptInterval;
}
public boolean isIgnoreInvalidExchanges() {
return ignoreInvalidExchanges;
}
public void setRejectOld(Boolean rejectOld) {
engine.setRejectOld(rejectOld);
}
public boolean isRejectOld() {
return engine.getRejectOld() != null && engine.getRejectOld();
}
/**
* Sets whether to ignore invalid exchanges which cannot be used by this stream resequencer.
*
* Default is false, by which an {@link CamelExchangeException} is thrown if the {@link Exchange}
* is invalid.
*/
public void setIgnoreInvalidExchanges(boolean ignoreInvalidExchanges) {
this.ignoreInvalidExchanges = ignoreInvalidExchanges;
}
@Override
public String toString() {
return "StreamResequencer[to: " + processor + "]";
}
@Override
public String getTraceLabel() {
return "streamResequence";
}
@Override
public String getId() {
return id;
}
@Override
public void setId(String id) {
this.id = id;
}
@Override
protected void doStart() throws Exception {
ServiceHelper.startService(processor);
delivery = new Delivery();
engine.start();
delivery.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.stopService(processor);
}
/**
* Sends the exchange to the next processor.
*
* @param exchange exchange to send.
*/
@Override
public void sendElement(Exchange exchange) throws Exception {
processor.process(exchange);
}
@Override
public boolean process(Exchange exchange, AsyncCallback callback) {
while (engine.size() >= capacity) {
try {
Thread.sleep(getTimeout());
} catch (InterruptedException e) {
// we was interrupted so break out
exchange.setException(e);
callback.done(true);
return true;
}
}
try {
engine.insert(exchange);
delivery.request();
} catch (Exception e) {
if (isIgnoreInvalidExchanges()) {
log.debug("Invalid Exchange. This Exchange will be ignored: {}", exchange);
} else {
exchange.setException(new CamelExchangeException("Error processing Exchange in StreamResequencer", exchange, e));
}
}
callback.done(true);
return true;
}
@Override
public boolean hasNext() {
return processor != null;
}
@Override
public List next() {
if (!hasNext()) {
return null;
}
List answer = new ArrayList<>(1);
answer.add(processor);
return answer;
}
class Delivery extends Thread {
private Lock deliveryRequestLock = new ReentrantLock();
private Condition deliveryRequestCondition = deliveryRequestLock.newCondition();
Delivery() {
super(camelContext.getExecutorServiceManager().resolveThreadName("Resequencer Delivery"));
}
@Override
public void run() {
while (isRunAllowed()) {
try {
deliveryRequestLock.lock();
try {
deliveryRequestCondition.await(deliveryAttemptInterval, TimeUnit.MILLISECONDS);
} finally {
deliveryRequestLock.unlock();
}
} catch (InterruptedException e) {
break;
}
try {
engine.deliver();
} catch (Throwable t) {
// a fail safe to handle all exceptions being thrown
getExceptionHandler().handleException(t);
}
}
}
public void cancel() {
interrupt();
}
public void request() {
deliveryRequestLock.lock();
try {
deliveryRequestCondition.signal();
} finally {
deliveryRequestLock.unlock();
}
}
}
}