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 */
017package org.apache.camel.impl;
018
019import java.util.concurrent.ScheduledExecutorService;
020
021import org.apache.camel.BatchConsumer;
022import org.apache.camel.Endpoint;
023import org.apache.camel.Exchange;
024import org.apache.camel.Processor;
025import org.apache.camel.ShutdownRunningTask;
026import org.apache.camel.spi.ShutdownAware;
027import org.apache.camel.spi.UriParam;
028import org.slf4j.Logger;
029import org.slf4j.LoggerFactory;
030
031/**
032 * A useful base class for any consumer which is polling batch based
033 */
034public abstract class ScheduledBatchPollingConsumer extends ScheduledPollConsumer implements BatchConsumer, ShutdownAware {
035    private static final Logger LOG = LoggerFactory.getLogger(ScheduledBatchPollingConsumer.class);
036    protected volatile ShutdownRunningTask shutdownRunningTask;
037    protected volatile int pendingExchanges;
038    @UriParam
039    protected int maxMessagesPerPoll;
040
041    public ScheduledBatchPollingConsumer(Endpoint endpoint, Processor processor) {
042        super(endpoint, processor);
043    }
044
045    public ScheduledBatchPollingConsumer(Endpoint endpoint, Processor processor, ScheduledExecutorService executor) {
046        super(endpoint, processor, executor);
047    }
048
049    @Override
050    public boolean deferShutdown(ShutdownRunningTask shutdownRunningTask) {
051        // store a reference what to do in case when shutting down and we have pending messages
052        this.shutdownRunningTask = shutdownRunningTask;
053        // do not defer shutdown
054        return false;
055    }
056
057    @Override
058    public int getPendingExchangesSize() {
059        int answer;
060        // only return the real pending size in case we are configured to complete all tasks
061        if (ShutdownRunningTask.CompleteAllTasks == shutdownRunningTask) {
062            answer = pendingExchanges;
063        } else {
064            answer = 0;
065        }
066
067        if (answer == 0 && isPolling()) {
068            // force at least one pending exchange if we are polling as there is a little gap
069            // in the processBatch method and until an exchange gets enlisted as in-flight
070            // which happens later, so we need to signal back to the shutdown strategy that
071            // there is a pending exchange. When we are no longer polling, then we will return 0
072            LOG.trace("Currently polling so returning 1 as pending exchanges");
073            answer = 1;
074        }
075
076        return answer;
077    }
078
079    @Override
080    public void prepareShutdown(boolean forced) {
081        // reset task as the state of the task is not to be preserved
082        // which otherwise may cause isBatchAllowed() to return a wrong answer
083        this.shutdownRunningTask = null;
084    }
085
086    @Override
087    public void setMaxMessagesPerPoll(int maxMessagesPerPoll) {
088        this.maxMessagesPerPoll = maxMessagesPerPoll;
089    }
090
091    /**
092     * Gets the maximum number of messages as a limit to poll at each polling.
093     * <p/>
094     * Is default unlimited, but use 0 or negative number to disable it as unlimited.
095     *
096     * @return max messages to poll
097     */
098    public int getMaxMessagesPerPoll() {
099        return maxMessagesPerPoll;
100    }
101
102    @Override
103    public boolean isBatchAllowed() {
104        // stop if we are not running
105        boolean answer = isRunAllowed();
106        if (!answer) {
107            return false;
108        }
109
110        if (shutdownRunningTask == null) {
111            // we are not shutting down so continue to run
112            return true;
113        }
114
115        // we are shutting down so only continue if we are configured to complete all tasks
116        return ShutdownRunningTask.CompleteAllTasks == shutdownRunningTask;
117    }
118
119    @Override
120    protected void processEmptyMessage() throws Exception {
121        Exchange exchange = getEndpoint().createExchange();
122        // enrich exchange, so we send an empty message with the batch details
123        exchange.setProperty(Exchange.BATCH_INDEX, 0);
124        exchange.setProperty(Exchange.BATCH_SIZE, 1);
125        exchange.setProperty(Exchange.BATCH_COMPLETE, true);
126        log.debug("Sending empty message as there were no messages from polling: {}", this.getEndpoint());
127        getProcessor().process(exchange);
128    }
129}