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.concurrent.ScheduledExecutorService;
020    
021    import org.apache.camel.BatchConsumer;
022    import org.apache.camel.Endpoint;
023    import org.apache.camel.Exchange;
024    import org.apache.camel.Processor;
025    import org.apache.camel.ShutdownRunningTask;
026    import org.apache.camel.spi.ShutdownAware;
027    import org.slf4j.Logger;
028    import org.slf4j.LoggerFactory;
029    
030    /**
031     * A useful base class for any consumer which is polling batch based
032     */
033    public abstract class ScheduledBatchPollingConsumer extends ScheduledPollConsumer implements BatchConsumer, ShutdownAware {
034        private static final transient Logger LOG = LoggerFactory.getLogger(ScheduledBatchPollingConsumer.class);
035        protected volatile ShutdownRunningTask shutdownRunningTask;
036        protected volatile int pendingExchanges;
037        protected int maxMessagesPerPoll;
038    
039        public ScheduledBatchPollingConsumer(Endpoint endpoint, Processor processor) {
040            super(endpoint, processor);
041        }
042    
043        public ScheduledBatchPollingConsumer(Endpoint endpoint, Processor processor, ScheduledExecutorService executor) {
044            super(endpoint, processor, executor);
045        }
046    
047        @Override
048        public boolean deferShutdown(ShutdownRunningTask shutdownRunningTask) {
049            // store a reference what to do in case when shutting down and we have pending messages
050            this.shutdownRunningTask = shutdownRunningTask;
051            // do not defer shutdown
052            return false;
053        }
054    
055        @Override
056        public int getPendingExchangesSize() {
057            int answer;
058            // only return the real pending size in case we are configured to complete all tasks
059            if (ShutdownRunningTask.CompleteAllTasks == shutdownRunningTask) {
060                answer = pendingExchanges;
061            } else {
062                answer = 0;
063            }
064    
065            if (answer == 0 && isPolling()) {
066                // force at least one pending exchange if we are polling as there is a little gap
067                // in the processBatch method and until an exchange gets enlisted as in-flight
068                // which happens later, so we need to signal back to the shutdown strategy that
069                // there is a pending exchange. When we are no longer polling, then we will return 0
070                LOG.trace("Currently polling so returning 1 as pending exchanges");
071                answer = 1;
072            }
073    
074            return answer;
075        }
076    
077        @Override
078        public void prepareShutdown(boolean forced) {
079            // reset task as the state of the task is not to be preserved
080            // which otherwise may cause isBatchAllowed() to return a wrong answer
081            this.shutdownRunningTask = null;
082        }
083    
084        @Override
085        public void setMaxMessagesPerPoll(int maxMessagesPerPoll) {
086            this.maxMessagesPerPoll = maxMessagesPerPoll;
087        }
088    
089        /**
090         * Gets the maximum number of messages as a limit to poll at each polling.
091         * <p/>
092         * Is default unlimited, but use 0 or negative number to disable it as unlimited.
093         *
094         * @return max messages to poll
095         */
096        public int getMaxMessagesPerPoll() {
097            return maxMessagesPerPoll;
098        }
099    
100        @Override
101        public boolean isBatchAllowed() {
102            // stop if we are not running
103            boolean answer = isRunAllowed();
104            if (!answer) {
105                return false;
106            }
107    
108            if (shutdownRunningTask == null) {
109                // we are not shutting down so continue to run
110                return true;
111            }
112    
113            // we are shutting down so only continue if we are configured to complete all tasks
114            return ShutdownRunningTask.CompleteAllTasks == shutdownRunningTask;
115        }
116    
117        @Override
118        protected void processEmptyMessage() throws Exception {
119            Exchange exchange = getEndpoint().createExchange();
120            // enrich exchange, so we send an empty message with the batch details
121            exchange.setProperty(Exchange.BATCH_INDEX, 0);
122            exchange.setProperty(Exchange.BATCH_SIZE, 1);
123            exchange.setProperty(Exchange.BATCH_COMPLETE, true);
124            log.debug("Sending empty message as there were no messages from polling: {}", this.getEndpoint());
125            getProcessor().process(exchange);
126        }
127    }