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.Timer;
020    import java.util.TimerTask;
021    import java.util.concurrent.RejectedExecutionException;
022    
023    import org.apache.camel.AsyncCallback;
024    import org.apache.camel.AsyncProcessor;
025    import org.apache.camel.Exchange;
026    import org.apache.camel.Message;
027    import org.apache.camel.Predicate;
028    import org.apache.camel.Processor;
029    import org.apache.camel.impl.converter.AsyncProcessorTypeConverter;
030    import org.apache.camel.model.ExceptionType;
031    import org.apache.camel.model.LoggingLevel;
032    import org.apache.camel.processor.exceptionpolicy.ExceptionPolicyStrategy;
033    import org.apache.camel.util.AsyncProcessorHelper;
034    import org.apache.camel.util.MessageHelper;
035    import org.apache.camel.util.ServiceHelper;
036    import org.apache.commons.logging.Log;
037    import org.apache.commons.logging.LogFactory;
038    
039    /**
040     * Implements a <a
041     * href="http://activemq.apache.org/camel/dead-letter-channel.html">Dead Letter
042     * Channel</a> after attempting to redeliver the message using the
043     * {@link RedeliveryPolicy}
044     *
045     * @version $Revision: 740263 $
046     */
047    public class DeadLetterChannel extends ErrorHandlerSupport implements AsyncProcessor {
048        public static final String REDELIVERY_COUNTER = "org.apache.camel.RedeliveryCounter";
049        public static final String REDELIVERED = "org.apache.camel.Redelivered";
050        public static final String EXCEPTION_CAUSE_PROPERTY = "CamelCauseException";
051        public static final String CAUGHT_EXCEPTION_HEADER = "org.apache.camel.CamelCaughtException";    
052        
053        private static final transient Log LOG = LogFactory.getLog(DeadLetterChannel.class);
054        private static final String FAILURE_HANDLED_PROPERTY = DeadLetterChannel.class.getName() + ".FAILURE_HANDLED";
055        
056        private static Timer timer = new Timer();
057        private Processor output;
058        private Processor deadLetter;
059        private AsyncProcessor outputAsync;
060        private RedeliveryPolicy redeliveryPolicy;
061        private Logger logger;
062        private Processor redeliveryProcessor;
063    
064        private class RedeliveryData {
065            int redeliveryCounter;
066            long redeliveryDelay;
067            boolean sync = true;
068            Predicate handledPredicate;
069    
070            // default behavior which can be overloaded on a per exception basis
071            RedeliveryPolicy currentRedeliveryPolicy = redeliveryPolicy;
072            Processor failureProcessor = deadLetter;
073        }
074        
075        private class RedeliverTimerTask extends TimerTask {
076            private final Exchange exchange;
077            private final AsyncCallback callback;
078            private final RedeliveryData data;
079            
080            public RedeliverTimerTask(Exchange exchange, AsyncCallback callback, RedeliveryData data) {
081                this.exchange = exchange;
082                this.callback = callback;
083                this.data = data;
084            }
085    
086            @Override
087            public void run() {
088                //only handle the real AsyncProcess the exchange 
089                outputAsync.process(exchange, new AsyncCallback() {
090                    public void done(boolean sync) {
091                        // Only handle the async case...
092                        if (sync) {
093                            return;
094                        }
095                        data.sync = false;
096                        // only process if the exchange hasn't failed
097                        // and it has not been handled by the error processor
098                        if (exchange.getException() != null && !isFailureHandled(exchange)) {
099                            // if we are redelivering then sleep before trying again
100                            asyncProcess(exchange, callback, data);
101                        } else {
102                            callback.done(sync);
103                        }
104                    }
105                });                
106            } 
107        }
108    
109        public DeadLetterChannel(Processor output, Processor deadLetter, Processor redeliveryProcessor, RedeliveryPolicy redeliveryPolicy, Logger logger, ExceptionPolicyStrategy exceptionPolicyStrategy) {
110            this.output = output;
111            this.deadLetter = deadLetter;
112            this.redeliveryProcessor = redeliveryProcessor;
113            this.outputAsync = AsyncProcessorTypeConverter.convert(output);
114            this.redeliveryPolicy = redeliveryPolicy;
115            this.logger = logger;
116            setExceptionPolicy(exceptionPolicyStrategy);
117        }
118    
119        public static <E extends Exchange> Logger createDefaultLogger() {
120            return new Logger(LOG, LoggingLevel.ERROR);
121        }
122    
123        @Override
124        public String toString() {
125            return "DeadLetterChannel[" + output + ", " + deadLetter + "]";
126        }
127    
128        public void process(Exchange exchange) throws Exception {
129            AsyncProcessorHelper.process(this, exchange);
130        }
131    
132        public boolean process(Exchange exchange, final AsyncCallback callback) {
133            return process(exchange, callback, new RedeliveryData());
134        }
135    
136        /**
137         * Processes the exchange using decorated with this dead letter channel.
138         */
139        protected boolean process(final Exchange exchange, final AsyncCallback callback, final RedeliveryData data) {
140    
141            while (true) {
142                // we can't keep retrying if the route is being shutdown.
143                if (!isRunAllowed()) {
144                    if (exchange.getException() == null) {
145                        exchange.setException(new RejectedExecutionException());
146                    }
147                    callback.done(data.sync);
148                    return data.sync;
149                }
150    
151                // if the exchange is transacted then let the underlying system handle the redelivery etc.
152                // this DeadLetterChannel is only for non transacted exchanges
153                if (exchange.isTransacted() && exchange.getException() != null) {
154                    if (LOG.isDebugEnabled()) {
155                        LOG.debug("This is a transacted exchange, bypassing this DeadLetterChannel: " + this + " for exchange: " + exchange);
156                    }
157                    return data.sync;
158                }
159    
160                // did previous processing caused an exception?
161                if (exchange.getException() != null) {
162                    handleException(exchange, data);
163                }
164    
165                // compute if we should redeliver or not
166                boolean shouldRedeliver = shouldRedeliver(exchange, data);
167                if (!shouldRedeliver) {
168                    return deliverToFaultProcessor(exchange, callback, data);
169                }
170    
171                // if we are redelivering then sleep before trying again
172                if (data.redeliveryCounter > 0) {
173                    // okay we will give it another go so clear the exception so we can try again
174                    if (exchange.getException() != null) {
175                        exchange.setException(null);
176                    }
177    
178                    // reset cached streams so they can be read again
179                    MessageHelper.resetStreamCache(exchange.getIn());
180    
181                    // wait until we should redeliver
182                    data.redeliveryDelay = data.currentRedeliveryPolicy.sleep(data.redeliveryDelay);
183    
184                    // letting onRedeliver be executed
185                    deliverToRedeliveryProcessor(exchange, callback, data);
186                }
187    
188                // process the exchange
189                boolean sync = outputAsync.process(exchange, new AsyncCallback() {
190                    public void done(boolean sync) {
191                        // Only handle the async case...
192                        if (sync) {
193                            return;
194                        }
195                        data.sync = false;
196                        // only process if the exchange hasn't failed
197                        // and it has not been handled by the error processor
198                        if (exchange.getException() != null && !isFailureHandled(exchange)) {                        
199                            //TODO Call the Timer for the asyncProcessor
200                            asyncProcess(exchange, callback, data);
201                        } else {
202                            callback.done(sync);
203                        }
204                    }
205                });
206                if (!sync) {
207                    // It is going to be processed async..
208                    return false;
209                }
210                if (exchange.getException() == null || isFailureHandled(exchange)) {
211                    // If everything went well.. then we exit here..
212                    callback.done(true);
213                    return true;
214                }
215                // error occurred so loop back around.....
216            }
217    
218        }
219    
220        protected void asyncProcess(final Exchange exchange, final AsyncCallback callback, final RedeliveryData data) {
221            // set the timer here
222            if (!isRunAllowed()) {
223                if (exchange.getException() == null) {
224                    exchange.setException(new RejectedExecutionException());
225                }
226                callback.done(data.sync);
227                return;
228            }
229    
230            // if the exchange is transacted then let the underlying system handle the redelivery etc.
231            // this DeadLetterChannel is only for non transacted exchanges
232            if (exchange.isTransacted() && exchange.getException() != null) {
233                if (LOG.isDebugEnabled()) {
234                    LOG.debug("This is a transacted exchange, bypassing this DeadLetterChannel: " + this + " for exchange: " + exchange);
235                }
236                return;
237            }
238            
239            // did previous processing caused an exception?
240            if (exchange.getException() != null) {
241                handleException(exchange, data);
242            }
243            
244            // compute if we should redeliver or not
245            boolean shouldRedeliver = shouldRedeliver(exchange, data);
246            if (!shouldRedeliver) {
247                deliverToFaultProcessor(exchange, callback, data);
248                return;
249            }
250            
251            // process the next try
252            // if we are redelivering then sleep before trying again
253            if (data.redeliveryCounter > 0) {
254                // okay we will give it another go so clear the exception so we can try again
255                if (exchange.getException() != null) {
256                    exchange.setException(null);
257                }
258                // wait until we should redeliver
259                data.redeliveryDelay = data.currentRedeliveryPolicy.getRedeliveryDelay(data.redeliveryDelay);
260                timer.schedule(new RedeliverTimerTask(exchange, callback, data), data.redeliveryDelay);
261    
262                // letting onRedeliver be executed
263                deliverToRedeliveryProcessor(exchange, callback, data);
264            }
265        }
266        
267        private void handleException(Exchange exchange, RedeliveryData data) {
268            Throwable e = exchange.getException();
269            // set the original caused exception
270            exchange.setProperty(EXCEPTION_CAUSE_PROPERTY, e);
271    
272            // find the error handler to use (if any)
273            ExceptionType exceptionPolicy = getExceptionPolicy(exchange, e);
274            if (exceptionPolicy != null) {
275                data.currentRedeliveryPolicy = exceptionPolicy.createRedeliveryPolicy(exchange.getContext(), data.currentRedeliveryPolicy);
276                data.handledPredicate = exceptionPolicy.getHandledPolicy();
277                Processor processor = exceptionPolicy.getErrorHandler();
278                if (processor != null) {
279                    data.failureProcessor = processor;
280                }
281            }
282    
283            String msg = "Failed delivery for exchangeId: " + exchange.getExchangeId()
284                    + ". On delivery attempt: " + data.redeliveryCounter + " caught: " + e;
285            logFailedDelivery(true, exchange, msg, data, e);
286    
287            data.redeliveryCounter = incrementRedeliveryCounter(exchange, e);
288        }
289    
290        /**
291         * Gives an optional configure redelivery processor a chance to process before the Exchange
292         * will be redelivered. This can be used to alter the Exchange.
293         */
294        private boolean deliverToRedeliveryProcessor(final Exchange exchange, final AsyncCallback callback,
295                                                final RedeliveryData data) {
296            if (redeliveryProcessor == null) {
297                return true;
298            }
299    
300            if (LOG.isTraceEnabled()) {
301                LOG.trace("RedeliveryProcessor " + redeliveryProcessor + " is processing Exchange before its redelivered");
302            }
303            AsyncProcessor afp = AsyncProcessorTypeConverter.convert(redeliveryProcessor);
304            boolean sync = afp.process(exchange, new AsyncCallback() {
305                public void done(boolean sync) {
306                    callback.done(data.sync);
307                }
308            });
309    
310            return sync;
311        }
312    
313        private boolean deliverToFaultProcessor(final Exchange exchange, final AsyncCallback callback,
314                                                final RedeliveryData data) {
315            // we did not success with the redelivery so now we let the failure processor handle it
316            setFailureHandled(exchange);
317            // must decrement the redelivery counter as we didn't process the redelivery but is
318            // handling by the failure handler. So we must -1 to not let the counter be out-of-sync
319            decrementRedeliveryCounter(exchange);
320    
321            AsyncProcessor afp = AsyncProcessorTypeConverter.convert(data.failureProcessor);
322            boolean sync = afp.process(exchange, new AsyncCallback() {
323                public void done(boolean sync) {
324                    restoreExceptionOnExchange(exchange, data.handledPredicate);
325                    callback.done(data.sync);
326                }
327            });
328    
329            String msg = "Failed delivery for exchangeId: " + exchange.getExchangeId()
330                    + ". Handled by the failure processor: " + data.failureProcessor;
331            logFailedDelivery(false, exchange, msg, data, null);
332    
333            return sync;
334        }
335    
336        // Properties
337        // -------------------------------------------------------------------------
338    
339        public static boolean isFailureHandled(Exchange exchange) {
340            return exchange.getProperty(FAILURE_HANDLED_PROPERTY) != null
341                || exchange.getIn().getHeader(CAUGHT_EXCEPTION_HEADER) != null;
342        }
343    
344        public static void setFailureHandled(Exchange exchange) {
345            exchange.setProperty(FAILURE_HANDLED_PROPERTY, exchange.getException());
346            exchange.getIn().setHeader(CAUGHT_EXCEPTION_HEADER, exchange.getException());
347            exchange.setException(null);
348        }
349    
350        /**
351         * Returns the output processor
352         */
353        public Processor getOutput() {
354            return output;
355        }
356    
357        /**
358         * Returns the dead letter that message exchanges will be sent to if the
359         * redelivery attempts fail
360         */
361        public Processor getDeadLetter() {
362            return deadLetter;
363        }
364    
365        public RedeliveryPolicy getRedeliveryPolicy() {
366            return redeliveryPolicy;
367        }
368    
369        /**
370         * Sets the redelivery policy
371         */
372        public void setRedeliveryPolicy(RedeliveryPolicy redeliveryPolicy) {
373            this.redeliveryPolicy = redeliveryPolicy;
374        }
375    
376        public Logger getLogger() {
377            return logger;
378        }
379    
380        /**
381         * Sets the logger strategy; which {@link Log} to use and which
382         * {@link LoggingLevel} to use
383         */
384        public void setLogger(Logger logger) {
385            this.logger = logger;
386        }
387    
388        // Implementation methods
389        // -------------------------------------------------------------------------
390    
391        protected static void restoreExceptionOnExchange(Exchange exchange, Predicate handledPredicate) {
392            if (handledPredicate == null || !handledPredicate.matches(exchange)) {
393                if (LOG.isDebugEnabled()) {
394                    LOG.debug("This exchange is not handled so its marked as failed: " + exchange);
395                }
396                // exception not handled, put exception back in the exchange
397                exchange.setException(exchange.getProperty(FAILURE_HANDLED_PROPERTY, Throwable.class));
398            } else {
399                if (LOG.isDebugEnabled()) {
400                    LOG.debug("This exchange is handled so its marked as not failed: " + exchange);
401                }
402                exchange.setProperty(Exchange.EXCEPTION_HANDLED_PROPERTY, Boolean.TRUE);
403            }
404        }
405    
406        private void logFailedDelivery(boolean shouldRedeliver, Exchange exchange, String message, RedeliveryData data, Throwable e) {
407            LoggingLevel newLogLevel;
408            if (shouldRedeliver) {
409                newLogLevel = data.currentRedeliveryPolicy.getRetryAttemptedLogLevel();
410            } else {
411                newLogLevel = data.currentRedeliveryPolicy.getRetriesExhaustedLogLevel();
412            }
413            if (e != null) {
414                logger.log(message, e, newLogLevel);
415            } else {
416                logger.log(message, newLogLevel);
417            }
418        }
419    
420        private boolean shouldRedeliver(Exchange exchange, RedeliveryData data) {
421            return data.currentRedeliveryPolicy.shouldRedeliver(data.redeliveryCounter);
422        }
423    
424        /**
425         * Increments the redelivery counter and adds the redelivered flag if the
426         * message has been redelivered
427         */
428        protected int incrementRedeliveryCounter(Exchange exchange, Throwable e) {
429            Message in = exchange.getIn();
430            Integer counter = in.getHeader(REDELIVERY_COUNTER, Integer.class);
431            int next = 1;
432            if (counter != null) {
433                next = counter + 1;
434            }
435            in.setHeader(REDELIVERY_COUNTER, next);
436            in.setHeader(REDELIVERED, Boolean.TRUE);
437            return next;
438        }
439    
440        /**
441         * Prepares the redelivery counter and boolean flag for the failure handle processor
442         */
443        private void decrementRedeliveryCounter(Exchange exchange) {
444            Message in = exchange.getIn();
445            Integer counter = in.getHeader(REDELIVERY_COUNTER, Integer.class);
446            if (counter != null) {
447                int prev = counter - 1;
448                in.setHeader(REDELIVERY_COUNTER, prev);
449                // set boolean flag according to counter
450                in.setHeader(REDELIVERED, prev > 0 ? Boolean.TRUE : Boolean.FALSE);
451            } else {
452                // not redelivered
453                in.setHeader(REDELIVERY_COUNTER, 0);
454                in.setHeader(REDELIVERED, Boolean.FALSE);
455            }
456        }
457    
458        @Override
459        protected void doStart() throws Exception {
460            ServiceHelper.startServices(output, deadLetter);
461        }
462    
463        @Override
464        protected void doStop() throws Exception {
465            ServiceHelper.stopServices(deadLetter, output);
466        }    
467        
468    }