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.impl;
018
019 import java.util.HashMap;
020 import java.util.Map;
021
022 import org.apache.camel.Consumer;
023 import org.apache.camel.Endpoint;
024 import org.apache.camel.Service;
025 import org.apache.camel.util.ServiceHelper;
026
027 /**
028 * A {@link org.apache.camel.spi.PollingConsumerPollStrategy} which supports suspending consumers if they
029 * failed for X number of times in a row.
030 * <p/>
031 * If Camel cannot successfully consumer from a given consumer, then after X consecutive failed attempts the consumer
032 * will be suspended/stopped. This prevents the log to get flooded with failed attempts, for example during nightly runs.
033 *
034 * @version
035 */
036 public class LimitedPollingConsumerPollStrategy extends DefaultPollingConsumerPollStrategy implements Service {
037
038 private final Map<Consumer, Integer> state = new HashMap<Consumer, Integer>();
039 private int limit = 3;
040
041 public int getLimit() {
042 return limit;
043 }
044
045 /**
046 * Sets the limit for how many straight rollbacks causes this strategy to suspend the fault consumer.
047 * <p/>
048 * When the consumer has been suspended, it has to be manually resumed/started to be active again.
049 * The limit is by default 3.
050 *
051 * @param limit the limit
052 */
053 public void setLimit(int limit) {
054 this.limit = limit;
055 }
056
057 @Override
058 public void commit(Consumer consumer, Endpoint endpoint, int polledMessages) {
059 // we could commit so clear state
060 state.remove(consumer);
061 }
062
063 public boolean rollback(Consumer consumer, Endpoint endpoint, int retryCounter, Exception cause) throws Exception {
064 // keep track how many times in a row we have rolled back
065 Integer times = state.get(consumer);
066 if (times == null) {
067 times = 1;
068 } else {
069 times += 1;
070 }
071 log.debug("Rollback occurred after {} times when consuming {}", times, endpoint);
072
073 boolean retry = false;
074
075 if (times >= limit) {
076 // clear state when we suspend so if its restarted manually we start all over again
077 state.remove(consumer);
078 onSuspend(consumer, endpoint);
079 } else {
080 // error occurred
081 state.put(consumer, times);
082 retry = onRollback(consumer, endpoint);
083 }
084
085 return retry;
086 }
087
088 /**
089 * The consumer is to be suspended because it exceeded the limit
090 *
091 * @param consumer the consumer
092 * @param endpoint the endpoint
093 * @throws Exception is thrown if error suspending the consumer
094 */
095 protected void onSuspend(Consumer consumer, Endpoint endpoint) throws Exception {
096 log.warn("Suspending consumer " + consumer + " after " + limit + " attempts to consume from " + endpoint
097 + ". You have to manually resume the consumer!");
098 ServiceHelper.suspendService(consumer);
099 }
100
101 /**
102 * Rollback occurred.
103 *
104 * @param consumer the consumer
105 * @param endpoint the endpoint
106 * @return whether or not to retry immediately, is default <tt>false</tt>
107 * @throws Exception can be thrown in case something goes wrong
108 */
109 protected boolean onRollback(Consumer consumer, Endpoint endpoint) throws Exception {
110 // do not retry by default
111 return false;
112 }
113
114 public void start() throws Exception {
115 // noop
116 }
117
118 public void stop() throws Exception {
119 state.clear();
120 }
121 }