001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.processor;
018
019 import java.util.ArrayList;
020 import java.util.List;
021 import java.util.concurrent.TimeUnit;
022 import java.util.concurrent.locks.Condition;
023 import java.util.concurrent.locks.Lock;
024 import java.util.concurrent.locks.ReentrantLock;
025
026 import org.apache.camel.Exchange;
027 import org.apache.camel.Navigate;
028 import org.apache.camel.Processor;
029 import org.apache.camel.impl.LoggingExceptionHandler;
030 import org.apache.camel.impl.ServiceSupport;
031 import org.apache.camel.processor.resequencer.ResequencerEngine;
032 import org.apache.camel.processor.resequencer.SequenceElementComparator;
033 import org.apache.camel.processor.resequencer.SequenceSender;
034 import org.apache.camel.spi.ExceptionHandler;
035 import org.apache.camel.util.ServiceHelper;
036
037 /**
038 * A resequencer that re-orders a (continuous) stream of {@link Exchange}s. The
039 * algorithm implemented by {@link ResequencerEngine} is based on the detection
040 * of gaps in a message stream rather than on a fixed batch size. Gap detection
041 * in combination with timeouts removes the constraint of having to know the
042 * number of messages of a sequence (i.e. the batch size) in advance.
043 * <p>
044 * Messages must contain a unique sequence number for which a predecessor and a
045 * successor is known. For example a message with the sequence number 3 has a
046 * predecessor message with the sequence number 2 and a successor message with
047 * the sequence number 4. The message sequence 2,3,5 has a gap because the
048 * sucessor of 3 is missing. The resequencer therefore has to retain message 5
049 * until message 4 arrives (or a timeout occurs).
050 * <p>
051 * Instances of this class poll for {@link Exchange}s from a given
052 * <code>endpoint</code>. Resequencing work and the delivery of messages to
053 * the next <code>processor</code> is done within the single polling thread.
054 *
055 * @author Martin Krasser
056 *
057 * @version $Revision: 769303 $
058 *
059 * @see ResequencerEngine
060 */
061 public class StreamResequencer extends ServiceSupport implements SequenceSender<Exchange>, Processor, Navigate<Processor> {
062
063 private static final long DELIVERY_ATTEMPT_INTERVAL = 1000L;
064
065 private final ExceptionHandler exceptionHandler;
066 private final ResequencerEngine<Exchange> engine;
067 private final Processor processor;
068 private Delivery delivery;
069 private int capacity;
070
071 /**
072 * Creates a new {@link StreamResequencer} instance.
073 *
074 * @param processor next processor that processes re-ordered exchanges.
075 * @param comparator a sequence element comparator for exchanges.
076 */
077 public StreamResequencer(Processor processor, SequenceElementComparator<Exchange> comparator) {
078 this.exceptionHandler = new LoggingExceptionHandler(getClass());
079 this.engine = new ResequencerEngine<Exchange>(comparator);
080 this.engine.setSequenceSender(this);
081 this.processor = processor;
082 }
083
084 /**
085 * Returns this resequencer's exception handler.
086 */
087 public ExceptionHandler getExceptionHandler() {
088 return exceptionHandler;
089 }
090
091 /**
092 * Returns the next processor.
093 */
094 public Processor getProcessor() {
095 return processor;
096 }
097
098 /**
099 * Returns this resequencer's capacity. The capacity is the maximum number
100 * of exchanges that can be managed by this resequencer at a given point in
101 * time. If the capacity if reached, polling from the endpoint will be
102 * skipped for <code>timeout</code> milliseconds giving exchanges the
103 * possibility to time out and to be delivered after the waiting period.
104 *
105 * @return this resequencer's capacity.
106 */
107 public int getCapacity() {
108 return capacity;
109 }
110
111 /**
112 * Returns this resequencer's timeout. This sets the resequencer engine's
113 * timeout via {@link ResequencerEngine#setTimeout(long)}. This value is
114 * also used to define the polling timeout from the endpoint.
115 *
116 * @return this resequencer's timeout. (Processor)
117 * @see ResequencerEngine#setTimeout(long)
118 */
119 public long getTimeout() {
120 return engine.getTimeout();
121 }
122
123 public void setCapacity(int capacity) {
124 this.capacity = capacity;
125 }
126
127 public void setTimeout(long timeout) {
128 engine.setTimeout(timeout);
129 }
130
131 @Override
132 public String toString() {
133 return "StreamResequencer[to: " + processor + "]";
134 }
135
136 @Override
137 protected void doStart() throws Exception {
138 ServiceHelper.startServices(processor);
139 delivery = new Delivery();
140 engine.start();
141 delivery.start();
142 }
143
144 @Override
145 protected void doStop() throws Exception {
146 // let's stop everything in the reverse order
147 // no need to stop the worker thread -- it will stop automatically when this service is stopped
148 engine.stop();
149 ServiceHelper.stopServices(processor);
150 }
151
152 /**
153 * Sends the <code>exchange</code> to the next <code>processor</code>.
154 *
155 * @param exchange exchange to send.
156 */
157 public void sendElement(Exchange exchange) throws Exception {
158 processor.process(exchange);
159 }
160
161 public void process(Exchange exchange) throws Exception {
162 while (engine.size() >= capacity) {
163 Thread.sleep(getTimeout());
164 }
165 engine.insert(exchange);
166 delivery.request();
167 }
168
169 public boolean hasNext() {
170 return processor != null;
171 }
172
173 public List<Processor> next() {
174 if (!hasNext()) {
175 return null;
176 }
177 List<Processor> answer = new ArrayList<Processor>(1);
178 answer.add(processor);
179 return answer;
180 }
181
182 private class Delivery extends Thread {
183
184 private Lock deliveryRequestLock = new ReentrantLock();
185 private Condition deliveryRequestCondition = deliveryRequestLock.newCondition();
186
187 public Delivery() {
188 super("Resequencer Delivery Thread");
189 }
190
191 @Override
192 public void run() {
193 while (true) {
194 try {
195 deliveryRequestLock.lock();
196 try {
197 deliveryRequestCondition.await(DELIVERY_ATTEMPT_INTERVAL, TimeUnit.MILLISECONDS);
198 } finally {
199 deliveryRequestLock.unlock();
200 }
201 } catch (InterruptedException e) {
202 break;
203 }
204 try {
205 engine.deliver();
206 } catch (Exception e) {
207 exceptionHandler.handleException(e);
208 }
209 }
210 }
211
212 public void cancel() {
213 interrupt();
214 }
215
216 public void request() {
217 deliveryRequestLock.lock();
218 try {
219 deliveryRequestCondition.signal();
220 } finally {
221 deliveryRequestLock.unlock();
222 }
223 }
224
225 }
226
227 }