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 import org.apache.camel.util.concurrent.ExecutorServiceHelper;
037
038 /**
039 * A resequencer that re-orders a (continuous) stream of {@link Exchange}s. The
040 * algorithm implemented by {@link ResequencerEngine} is based on the detection
041 * of gaps in a message stream rather than on a fixed batch size. Gap detection
042 * in combination with timeouts removes the constraint of having to know the
043 * number of messages of a sequence (i.e. the batch size) in advance.
044 * <p>
045 * Messages must contain a unique sequence number for which a predecessor and a
046 * successor is known. For example a message with the sequence number 3 has a
047 * predecessor message with the sequence number 2 and a successor message with
048 * the sequence number 4. The message sequence 2,3,5 has a gap because the
049 * sucessor of 3 is missing. The resequencer therefore has to retain message 5
050 * until message 4 arrives (or a timeout occurs).
051 * <p>
052 * Instances of this class poll for {@link Exchange}s from a given
053 * <code>endpoint</code>. Resequencing work and the delivery of messages to
054 * the next <code>processor</code> is done within the single polling thread.
055 *
056 * @version $Revision: 836213 $
057 *
058 * @see ResequencerEngine
059 */
060 public class StreamResequencer extends ServiceSupport implements SequenceSender<Exchange>, Processor, Navigate<Processor>, Traceable {
061
062 private static final long DELIVERY_ATTEMPT_INTERVAL = 1000L;
063
064 private final ExceptionHandler exceptionHandler;
065 private final ResequencerEngine<Exchange> engine;
066 private final Processor processor;
067 private Delivery delivery;
068 private int capacity;
069
070 /**
071 * Creates a new {@link StreamResequencer} instance.
072 *
073 * @param processor next processor that processes re-ordered exchanges.
074 * @param comparator a sequence element comparator for exchanges.
075 */
076 public StreamResequencer(Processor processor, SequenceElementComparator<Exchange> comparator) {
077 this.exceptionHandler = new LoggingExceptionHandler(getClass());
078 this.engine = new ResequencerEngine<Exchange>(comparator);
079 this.engine.setSequenceSender(this);
080 this.processor = processor;
081 }
082
083 /**
084 * Returns this resequencer's exception handler.
085 */
086 public ExceptionHandler getExceptionHandler() {
087 return exceptionHandler;
088 }
089
090 /**
091 * Returns the next processor.
092 */
093 public Processor getProcessor() {
094 return processor;
095 }
096
097 /**
098 * Returns this resequencer's capacity. The capacity is the maximum number
099 * of exchanges that can be managed by this resequencer at a given point in
100 * time. If the capacity if reached, polling from the endpoint will be
101 * skipped for <code>timeout</code> milliseconds giving exchanges the
102 * possibility to time out and to be delivered after the waiting period.
103 *
104 * @return this resequencer's capacity.
105 */
106 public int getCapacity() {
107 return capacity;
108 }
109
110 /**
111 * Returns this resequencer's timeout. This sets the resequencer engine's
112 * timeout via {@link ResequencerEngine#setTimeout(long)}. This value is
113 * also used to define the polling timeout from the endpoint.
114 *
115 * @return this resequencer's timeout. (Processor)
116 * @see ResequencerEngine#setTimeout(long)
117 */
118 public long getTimeout() {
119 return engine.getTimeout();
120 }
121
122 public void setCapacity(int capacity) {
123 this.capacity = capacity;
124 }
125
126 public void setTimeout(long timeout) {
127 engine.setTimeout(timeout);
128 }
129
130 @Override
131 public String toString() {
132 return "StreamResequencer[to: " + processor + "]";
133 }
134
135 public String getTraceLabel() {
136 return "streamResequence";
137 }
138
139 @Override
140 protected void doStart() throws Exception {
141 ServiceHelper.startServices(processor);
142 delivery = new Delivery();
143 engine.start();
144 delivery.start();
145 }
146
147 @Override
148 protected void doStop() throws Exception {
149 // let's stop everything in the reverse order
150 // no need to stop the worker thread -- it will stop automatically when this service is stopped
151 engine.stop();
152 ServiceHelper.stopServices(processor);
153 }
154
155 /**
156 * Sends the <code>exchange</code> to the next <code>processor</code>.
157 *
158 * @param exchange exchange to send.
159 */
160 public void sendElement(Exchange exchange) throws Exception {
161 processor.process(exchange);
162 }
163
164 public void process(Exchange exchange) throws Exception {
165 while (engine.size() >= capacity) {
166 Thread.sleep(getTimeout());
167 }
168 engine.insert(exchange);
169 delivery.request();
170 }
171
172 public boolean hasNext() {
173 return processor != null;
174 }
175
176 public List<Processor> next() {
177 if (!hasNext()) {
178 return null;
179 }
180 List<Processor> answer = new ArrayList<Processor>(1);
181 answer.add(processor);
182 return answer;
183 }
184
185 private class Delivery extends Thread {
186
187 private Lock deliveryRequestLock = new ReentrantLock();
188 private Condition deliveryRequestCondition = deliveryRequestLock.newCondition();
189
190 public Delivery() {
191 super(ExecutorServiceHelper.getThreadName("Resequencer Delivery"));
192 }
193
194 @Override
195 public void run() {
196 while (isRunAllowed()) {
197 try {
198 deliveryRequestLock.lock();
199 try {
200 deliveryRequestCondition.await(DELIVERY_ATTEMPT_INTERVAL, TimeUnit.MILLISECONDS);
201 } finally {
202 deliveryRequestLock.unlock();
203 }
204 } catch (InterruptedException e) {
205 break;
206 }
207 try {
208 engine.deliver();
209 } catch (Exception e) {
210 exceptionHandler.handleException(e);
211 }
212 }
213 }
214
215 public void cancel() {
216 interrupt();
217 }
218
219 public void request() {
220 deliveryRequestLock.lock();
221 try {
222 deliveryRequestCondition.signal();
223 } finally {
224 deliveryRequestLock.unlock();
225 }
226 }
227
228 }
229
230 }