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.AsyncCallback;
027 import org.apache.camel.AsyncProcessor;
028 import org.apache.camel.CamelContext;
029 import org.apache.camel.CamelExchangeException;
030 import org.apache.camel.Exchange;
031 import org.apache.camel.Navigate;
032 import org.apache.camel.Processor;
033 import org.apache.camel.Traceable;
034 import org.apache.camel.impl.LoggingExceptionHandler;
035 import org.apache.camel.processor.resequencer.ResequencerEngine;
036 import org.apache.camel.processor.resequencer.SequenceElementComparator;
037 import org.apache.camel.processor.resequencer.SequenceSender;
038 import org.apache.camel.spi.ExceptionHandler;
039 import org.apache.camel.support.ServiceSupport;
040 import org.apache.camel.util.AsyncProcessorHelper;
041 import org.apache.camel.util.ObjectHelper;
042 import org.apache.camel.util.ServiceHelper;
043 import org.slf4j.Logger;
044 import org.slf4j.LoggerFactory;
045
046 /**
047 * A resequencer that re-orders a (continuous) stream of {@link Exchange}s. The
048 * algorithm implemented by {@link ResequencerEngine} is based on the detection
049 * of gaps in a message stream rather than on a fixed batch size. Gap detection
050 * in combination with timeouts removes the constraint of having to know the
051 * number of messages of a sequence (i.e. the batch size) in advance.
052 * <p>
053 * Messages must contain a unique sequence number for which a predecessor and a
054 * successor is known. For example a message with the sequence number 3 has a
055 * predecessor message with the sequence number 2 and a successor message with
056 * the sequence number 4. The message sequence 2,3,5 has a gap because the
057 * successor of 3 is missing. The resequencer therefore has to retain message 5
058 * until message 4 arrives (or a timeout occurs).
059 * <p>
060 * Instances of this class poll for {@link Exchange}s from a given
061 * <code>endpoint</code>. Resequencing work and the delivery of messages to
062 * the next <code>processor</code> is done within the single polling thread.
063 *
064 * @version
065 *
066 * @see ResequencerEngine
067 */
068 public class StreamResequencer extends ServiceSupport implements SequenceSender<Exchange>, AsyncProcessor, Navigate<Processor>, Traceable {
069
070 private static final long DELIVERY_ATTEMPT_INTERVAL = 1000L;
071 private static final Logger LOG = LoggerFactory.getLogger(StreamResequencer.class);
072
073 private final CamelContext camelContext;
074 private final ExceptionHandler exceptionHandler;
075 private final ResequencerEngine<Exchange> engine;
076 private final Processor processor;
077 private Delivery delivery;
078 private int capacity;
079 private boolean ignoreInvalidExchanges;
080
081 /**
082 * Creates a new {@link StreamResequencer} instance.
083 *
084 * @param processor next processor that processes re-ordered exchanges.
085 * @param comparator a sequence element comparator for exchanges.
086 */
087 public StreamResequencer(CamelContext camelContext, Processor processor, SequenceElementComparator<Exchange> comparator) {
088 ObjectHelper.notNull(camelContext, "CamelContext");
089 this.camelContext = camelContext;
090 this.engine = new ResequencerEngine<Exchange>(comparator);
091 this.engine.setSequenceSender(this);
092 this.processor = processor;
093 this.exceptionHandler = new LoggingExceptionHandler(camelContext, getClass());
094 }
095
096 /**
097 * Returns this resequencer's exception handler.
098 */
099 public ExceptionHandler getExceptionHandler() {
100 return exceptionHandler;
101 }
102
103 /**
104 * Returns the next processor.
105 */
106 public Processor getProcessor() {
107 return processor;
108 }
109
110 /**
111 * Returns this resequencer's capacity. The capacity is the maximum number
112 * of exchanges that can be managed by this resequencer at a given point in
113 * time. If the capacity if reached, polling from the endpoint will be
114 * skipped for <code>timeout</code> milliseconds giving exchanges the
115 * possibility to time out and to be delivered after the waiting period.
116 *
117 * @return this resequencer's capacity.
118 */
119 public int getCapacity() {
120 return capacity;
121 }
122
123 /**
124 * Returns this resequencer's timeout. This sets the resequencer engine's
125 * timeout via {@link ResequencerEngine#setTimeout(long)}. This value is
126 * also used to define the polling timeout from the endpoint.
127 *
128 * @return this resequencer's timeout. (Processor)
129 * @see ResequencerEngine#setTimeout(long)
130 */
131 public long getTimeout() {
132 return engine.getTimeout();
133 }
134
135 public void setCapacity(int capacity) {
136 this.capacity = capacity;
137 }
138
139 public void setTimeout(long timeout) {
140 engine.setTimeout(timeout);
141 }
142
143 public boolean isIgnoreInvalidExchanges() {
144 return ignoreInvalidExchanges;
145 }
146
147 public void setRejectOld(Boolean rejectOld) {
148 engine.setRejectOld(rejectOld);
149 }
150
151 /**
152 * Sets whether to ignore invalid exchanges which cannot be used by this stream resequencer.
153 * <p/>
154 * Default is <tt>false</tt>, by which an {@link CamelExchangeException} is thrown if the {@link Exchange}
155 * is invalid.
156 */
157 public void setIgnoreInvalidExchanges(boolean ignoreInvalidExchanges) {
158 this.ignoreInvalidExchanges = ignoreInvalidExchanges;
159 }
160
161 @Override
162 public String toString() {
163 return "StreamResequencer[to: " + processor + "]";
164 }
165
166 public String getTraceLabel() {
167 return "streamResequence";
168 }
169
170 @Override
171 protected void doStart() throws Exception {
172 ServiceHelper.startServices(processor);
173 delivery = new Delivery();
174 engine.start();
175 delivery.start();
176 }
177
178 @Override
179 protected void doStop() throws Exception {
180 // let's stop everything in the reverse order
181 // no need to stop the worker thread -- it will stop automatically when this service is stopped
182 engine.stop();
183 ServiceHelper.stopServices(processor);
184 }
185
186 /**
187 * Sends the <code>exchange</code> to the next <code>processor</code>.
188 *
189 * @param exchange exchange to send.
190 */
191 public void sendElement(Exchange exchange) throws Exception {
192 processor.process(exchange);
193 }
194
195 public void process(Exchange exchange) throws Exception {
196 AsyncProcessorHelper.process(this, exchange);
197 }
198
199 public boolean process(Exchange exchange, AsyncCallback callback) {
200 while (engine.size() >= capacity) {
201 try {
202 Thread.sleep(getTimeout());
203 } catch (InterruptedException e) {
204 // we was interrupted so break out
205 exchange.setException(e);
206 callback.done(true);
207 return true;
208 }
209 }
210
211 try {
212 engine.insert(exchange);
213 delivery.request();
214 } catch (Exception e) {
215 if (isIgnoreInvalidExchanges()) {
216 LOG.debug("Invalid Exchange. This Exchange will be ignored: {}", exchange);
217 } else {
218 exchange.setException(new CamelExchangeException("Error processing Exchange in StreamResequencer", exchange, e));
219 }
220 }
221
222 callback.done(true);
223 return true;
224 }
225
226 public boolean hasNext() {
227 return processor != null;
228 }
229
230 public List<Processor> next() {
231 if (!hasNext()) {
232 return null;
233 }
234 List<Processor> answer = new ArrayList<Processor>(1);
235 answer.add(processor);
236 return answer;
237 }
238
239 class Delivery extends Thread {
240
241 private Lock deliveryRequestLock = new ReentrantLock();
242 private Condition deliveryRequestCondition = deliveryRequestLock.newCondition();
243
244 public Delivery() {
245 super(camelContext.getExecutorServiceManager().resolveThreadName("Resequencer Delivery"));
246 }
247
248 @Override
249 public void run() {
250 while (isRunAllowed()) {
251 try {
252 deliveryRequestLock.lock();
253 try {
254 deliveryRequestCondition.await(DELIVERY_ATTEMPT_INTERVAL, TimeUnit.MILLISECONDS);
255 } finally {
256 deliveryRequestLock.unlock();
257 }
258 } catch (InterruptedException e) {
259 break;
260 }
261 try {
262 engine.deliver();
263 } catch (Throwable t) {
264 // a fail safe to handle all exceptions being thrown
265 getExceptionHandler().handleException(t);
266 }
267 }
268 }
269
270 public void cancel() {
271 interrupt();
272 }
273
274 public void request() {
275 deliveryRequestLock.lock();
276 try {
277 deliveryRequestCondition.signal();
278 } finally {
279 deliveryRequestLock.unlock();
280 }
281 }
282
283 }
284
285 }