Retrieve multiple messages from SQS

Question

I have multiple messages in SQS. The following code always returns only one, even if there are dozens visible (not in flight). setMaxNumberOfMessages I th

Answer 1

For small task list I use FIFO queue like stackoverflow.com/a/55149351/13678017 for example modified AWS tutorial

            // Create a queue.
        System.out.println("Creating a new Amazon SQS FIFO queue called " + "MyFifoQueue.fifo.\n");
        final Map<String, String> attributes = new HashMap<>();

        // A FIFO queue must have the FifoQueue attribute set to true.
        attributes.put("FifoQueue", "true");
        /*
         * If the user doesn't provide a MessageDeduplicationId, generate a
         * MessageDeduplicationId based on the content.
         */
        attributes.put("ContentBasedDeduplication", "true");
        // The FIFO queue name must end with the .fifo suffix.
        final CreateQueueRequest createQueueRequest = new CreateQueueRequest("MyFifoQueue4.fifo")
                        .withAttributes(attributes);
        final String myQueueUrl = sqs.createQueue(createQueueRequest).getQueueUrl();

        // List all queues.
        System.out.println("Listing all queues in your account.\n");
        for (final String queueUrl : sqs.listQueues().getQueueUrls()) {
            System.out.println("  QueueUrl: " + queueUrl);
        }
        System.out.println();

        // Send a message.
        System.out.println("Sending a message to MyQueue.\n");

        for (int i = 0; i < 4; i++) {

            var request = new SendMessageRequest()
                    .withQueueUrl(myQueueUrl)
                    .withMessageBody("message " + i)
                    .withMessageGroupId("userId1");
                    ;

            sqs.sendMessage(request);
        }

        for (int i = 0; i < 6; i++) {

            var request = new SendMessageRequest()
                    .withQueueUrl(myQueueUrl)
                    .withMessageBody("message " + i)
                    .withMessageGroupId("userId2");
                    ;

            sqs.sendMessage(request);
        }

        // Receive messages.
        System.out.println("Receiving messages from MyQueue.\n");
        var receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);

        receiveMessageRequest.setMaxNumberOfMessages(10);
        receiveMessageRequest.setWaitTimeSeconds(20);

        // what receive?
        receiveMessageRequest.withMessageAttributeNames("userId2");


        final List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
        for (final Message message : messages) {
            System.out.println("Message");
            System.out.println("  MessageId:     "
                    + message.getMessageId());
            System.out.println("  ReceiptHandle: "
                    + message.getReceiptHandle());
            System.out.println("  MD5OfBody:     "
                    + message.getMD5OfBody());
            System.out.println("  Body:          "
                    + message.getBody());
            for (final Entry<String, String> entry : message.getAttributes()
                    .entrySet()) {
                System.out.println("Attribute");
                System.out.println("  Name:  " + entry
                        .getKey());
                System.out.println("  Value: " + entry
                        .getValue());
            }
        }

Answer 2

Thanks Caoilte!

I faced this issue also. Finally solved by using long polling follow the configuration here: https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-configure-long-polling-for-queue.html

Unfortunately, to use long polling, you must create your queue as FIFO one. I tried standard queue with no luck.

And when receiving, need also set MaxNumberOfMessages. So my code is like:

ReceiveMessageRequest receive_request = new ReceiveMessageRequest() .withQueueUrl(QUEUE_URL) .withWaitTimeSeconds(20) .withMaxNumberOfMessages(10);

Although solved, still feel too wired. AWS should definitely provide a more neat API for this kind of basic receiving operation.

From my point, AWS has many many cool features but not good APIs. Like those guys are rushing out all the time.