AWS SQS Java. Not all messages are retrieved from the SQS queue

I've been trying to use AWS SDK for Java to retrieve all messages from the SQS queue I have learned about the distributed nature of AWS SQS, and messages are stored on different servers But I don't understand why this architecture won't be hidden by end users What skills do I need to apply in Java code to retrieve all messages and be 100% sure no one misses?

I try to use "long polling":

ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
for (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 (Entry<String,String> entry : message.getAttributes().entrySet()) {
System.out.println(" Attribute");
System.out.println(" Name: " + entry.getKey());
System.out.println(" Value: " + entry.getValue());
}
}
System.out.println();

This is similar to request batching / client buffering:

// Create the basic Amazon SQS async client
    AmazonSQSAsync sqsAsync = new AmazonSQSAsyncClient();

    // Create the buffered client
    AmazonSQSAsync bufferedSqs = new AmazonSQSBufferedAsyncClient(sqsAsync);

    CreateQueueRequest createRequest = new CreateQueueRequest().withQueueName("MyTestQueue");

    CreateQueueResult res = bufferedSqs.createQueue(createRequest);

    SendMessageRequest request = new SendMessageRequest();
    String body = "test message_" + System.currentTimeMillis();
    request.setMessageBody( body );
    request.setQueueUrl(res.getQueueUrl());

    SendMessageResult sendResult = bufferedSqs.sendMessage(request);

    ReceiveMessageRequest receiveRq = new ReceiveMessageRequest()
    .withMaxNumberOfMessages(10)
    .withQueueUrl(queueUrl);
    ReceiveMessageResult rx = bufferedSqs.receiveMessage(receiveRq);

    List<Message> messages = rx.getMessages();
    for (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 (Entry<String,String> entry : message.getAttributes().entrySet()) {
    System.out.println(" Attribute");
    System.out.println(" Name: " + entry.getKey());
    System.out.println(" Value: " + entry.getValue());
    }
    }

But I still can't retrieve all the messages

Any ideas?

AWS forum kept silent on my post

Solution

When receiving a message from the SQS queue, you need to call SQS: receivemessage repeatedly

Every time you call SQS: receivemessage, you will get 0 or more messages from the queue. You need to iterate over these messages For each message, you also need to call SQS: deletemessage to delete the message from the queue after processing each message

Add a loop around the "long polling" example above to receive all messages

for (;;) {
    ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
    List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
    for (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 (Entry<String,String> entry : message.getAttributes().entrySet()) {
            System.out.println(" Attribute");
            System.out.println(" Name: " + entry.getKey());
            System.out.println(" Value: " + entry.getValue());
        }
    }
    System.out.println();
}

Also note that you may receive the same message multiple times Therefore, allow your work to "reprocess" the same message or detect duplicate messages