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 * @version $Revision: 792319 $
056 *
057 * @see ResequencerEngine
058 */
059 public class StreamResequencer extends ServiceSupport implements SequenceSender<Exchange>, Processor, Navigate<Processor>, Traceable {
060
061 private static final long DELIVERY_ATTEMPT_INTERVAL = 1000L;
062
063 private final ExceptionHandler exceptionHandler;
064 private final ResequencerEngine<Exchange> engine;
065 private final Processor processor;
066 private Delivery delivery;
067 private int capacity;
068
069 /**
070 * Creates a new {@link StreamResequencer} instance.
071 *
072 * @param processor next processor that processes re-ordered exchanges.
073 * @param comparator a sequence element comparator for exchanges.
074 */
075 public StreamResequencer(Processor processor, SequenceElementComparator<Exchange> comparator) {
076 this.exceptionHandler = new LoggingExceptionHandler(getClass());
077 this.engine = new ResequencerEngine<Exchange>(comparator);
078 this.engine.setSequenceSender(this);
079 this.processor = processor;
080 }
081
082 /**
083 * Returns this resequencer's exception handler.
084 */
085 public ExceptionHandler getExceptionHandler() {
086 return exceptionHandler;
087 }
088
089 /**
090 * Returns the next processor.
091 */
092 public Processor getProcessor() {
093 return processor;
094 }
095
096 /**
097 * Returns this resequencer's capacity. The capacity is the maximum number
098 * of exchanges that can be managed by this resequencer at a given point in
099 * time. If the capacity if reached, polling from the endpoint will be
100 * skipped for <code>timeout</code> milliseconds giving exchanges the
101 * possibility to time out and to be delivered after the waiting period.
102 *
103 * @return this resequencer's capacity.
104 */
105 public int getCapacity() {
106 return capacity;
107 }
108
109 /**
110 * Returns this resequencer's timeout. This sets the resequencer engine's
111 * timeout via {@link ResequencerEngine#setTimeout(long)}. This value is
112 * also used to define the polling timeout from the endpoint.
113 *
114 * @return this resequencer's timeout. (Processor)
115 * @see ResequencerEngine#setTimeout(long)
116 */
117 public long getTimeout() {
118 return engine.getTimeout();
119 }
120
121 public void setCapacity(int capacity) {
122 this.capacity = capacity;
123 }
124
125 public void setTimeout(long timeout) {
126 engine.setTimeout(timeout);
127 }
128
129 @Override
130 public String toString() {
131 return "StreamResequencer[to: " + processor + "]";
132 }
133
134 public String getTraceLabel() {
135 return "StreamResequence";
136 }
137
138 @Override
139 protected void doStart() throws Exception {
140 ServiceHelper.startServices(processor);
141 delivery = new Delivery();
142 engine.start();
143 delivery.start();
144 }
145
146 @Override
147 protected void doStop() throws Exception {
148 // let's stop everything in the reverse order
149 // no need to stop the worker thread -- it will stop automatically when this service is stopped
150 engine.stop();
151 ServiceHelper.stopServices(processor);
152 }
153
154 /**
155 * Sends the <code>exchange</code> to the next <code>processor</code>.
156 *
157 * @param exchange exchange to send.
158 */
159 public void sendElement(Exchange exchange) throws Exception {
160 processor.process(exchange);
161 }
162
163 public void process(Exchange exchange) throws Exception {
164 while (engine.size() >= capacity) {
165 Thread.sleep(getTimeout());
166 }
167 engine.insert(exchange);
168 delivery.request();
169 }
170
171 public boolean hasNext() {
172 return processor != null;
173 }
174
175 public List<Processor> next() {
176 if (!hasNext()) {
177 return null;
178 }
179 List<Processor> answer = new ArrayList<Processor>(1);
180 answer.add(processor);
181 return answer;
182 }
183
184 private class Delivery extends Thread {
185
186 private Lock deliveryRequestLock = new ReentrantLock();
187 private Condition deliveryRequestCondition = deliveryRequestLock.newCondition();
188
189 public Delivery() {
190 super("Resequencer Delivery Thread");
191 }
192
193 @Override
194 public void run() {
195 while (true) {
196 try {
197 deliveryRequestLock.lock();
198 try {
199 deliveryRequestCondition.await(DELIVERY_ATTEMPT_INTERVAL, TimeUnit.MILLISECONDS);
200 } finally {
201 deliveryRequestLock.unlock();
202 }
203 } catch (InterruptedException e) {
204 break;
205 }
206 try {
207 engine.deliver();
208 } catch (Exception e) {
209 exceptionHandler.handleException(e);
210 }
211 }
212 }
213
214 public void cancel() {
215 interrupt();
216 }
217
218 public void request() {
219 deliveryRequestLock.lock();
220 try {
221 deliveryRequestCondition.signal();
222 } finally {
223 deliveryRequestLock.unlock();
224 }
225 }
226
227 }
228
229 }