com.amazon.sqs.javamessaging.acknowledge.RangedAcknowledger Maven / Gradle / Ivy

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The Amazon SQS Java Messaging Library holds the Java Message Service compatible classes, that are used for communicating with Amazon Simple Queue Service.
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/*
 * Copyright 2010-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */
package com.amazon.sqs.javamessaging.acknowledge;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicLong;

import javax.jms.JMSException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.amazon.sqs.javamessaging.AmazonSQSMessagingClientWrapper;
import com.amazon.sqs.javamessaging.SQSSession;
import com.amazon.sqs.javamessaging.message.SQSMessage;
import com.amazonaws.services.sqs.model.DeleteMessageBatchRequest;
import com.amazonaws.services.sqs.model.DeleteMessageBatchRequestEntry;

/**
 * Used to acknowledge group of messages. Acknowledging a consumed message
 * acknowledges all messages that the session has consumed before and including
 * that message.
 * 
 * A big backlog of consumed messages can cause memory pressure, as well as an
 * increase on the probability of duplicates.
 * 
 * This class is not safe for concurrent use.
 */
public class RangedAcknowledger extends BulkSQSOperation implements Acknowledger {
    private static final Log LOG = LogFactory.getLog(RangedAcknowledger.class);
    
    protected static final AtomicLong batchIdGenerator = new AtomicLong();

    private final AmazonSQSMessagingClientWrapper amazonSQSClient;

    private final SQSSession session;
    
    private final Queue unAckMessages;

    public RangedAcknowledger(AmazonSQSMessagingClientWrapper amazonSQSClient, SQSSession session) {
        this.amazonSQSClient = amazonSQSClient;
        this.session = session;
        this.unAckMessages  = new LinkedList();
    }
    
    /**
     * Acknowledges all the consumed messages as well as the previously consumed
     * messages on the session via calling deleteMessageBatch until
     * all the messages are deleted.
     */
    @Override
    public void acknowledge(SQSMessage message) throws JMSException {
        session.checkClosed();

        SQSMessageIdentifier ackMessage = new SQSMessageIdentifier(
                message.getQueueUrl(), message.getReceiptHandle(), message.getSQSMessageId());

        int indexOfMessage = indexOf(ackMessage);

        /**
         * In case the message has already been deleted, warn user about it and
         * return. If not then then it should continue with acknowledging all
         * the messages received before that
         */
        if (indexOfMessage == -1) {
            LOG.warn("SQSMessageID: " + message.getSQSMessageId() + " with SQSMessageReceiptHandle: " +
                     message.getReceiptHandle() + " does not exist.");
        } else {
            bulkAction(getUnAckMessages(), indexOfMessage);
        }
    }

    /**
     * Return the index of message if the message is in queue. Return -1 if
     * message does not exist in queue.
     */
    private int indexOf(SQSMessageIdentifier findMessage) {
        int i = 0;
        for (SQSMessageIdentifier sqsMessageIdentifier : unAckMessages) {
            i++;
            if (sqsMessageIdentifier.equals(findMessage)) {
                return i;
            }
        }
        return -1;
    }
    
    /**
     * Updates the internal queue for the consumed but not acknowledged
     * messages if the message was not already on queue.
     */
    @Override
    public void notifyMessageReceived(SQSMessage message) throws JMSException {
        SQSMessageIdentifier messageIdentifier = new SQSMessageIdentifier(
                message.getQueueUrl(), message.getReceiptHandle(), message.getSQSMessageId());
        if (!unAckMessages.contains(messageIdentifier)) {
            unAckMessages.add(messageIdentifier);
        }
    } 
    
    /**
     * Returns the list of all consumed but not acknowledged messages.
     */
    @Override
    public List getUnAckMessages() {
        return new ArrayList(unAckMessages);
    }
    
    /**
     * Clears the list of not acknowledged messages.
     */
    @Override
    public void forgetUnAckMessages() {
        unAckMessages.clear();
    }
    
    /**
     * Acknowledges up to 10 messages via calling
     * deleteMessageBatch.
     */
    @Override
    public void action(String queueUrl, List receiptHandles) throws JMSException {
        if (receiptHandles == null || receiptHandles.isEmpty()) {
            return;
        }

        List deleteMessageBatchRequestEntries = new ArrayList();
        for (String receiptHandle : receiptHandles) {
            // Remove the message from queue of unAckMessages
            unAckMessages.poll();
            
            DeleteMessageBatchRequestEntry entry = new DeleteMessageBatchRequestEntry(
                    Long.toString(batchIdGenerator.incrementAndGet()), receiptHandle);
            deleteMessageBatchRequestEntries.add(entry);
        }
        
        DeleteMessageBatchRequest deleteMessageBatchRequest = new DeleteMessageBatchRequest(
                queueUrl, deleteMessageBatchRequestEntries);
        /**
         * TODO: If one of the batch calls fail, then the remaining messages on
         * the batch will not be deleted, and will be visible and delivered as
         * duplicate after visibility timeout expires.
         */
        amazonSQSClient.deleteMessageBatch(deleteMessageBatchRequest);
    }
}