How does Amazon's SQS notify one of my "worker" servers whenever there is something in the queue?

Question

I'm following this tutorial: http://boto.s3.amazonaws.com/sqs_tut.html

When there's something in the queue, how do I assign one of my 20 workers to process it?

I'm using Python.

Answer 1

Unfortunately, SQS lacks some of the semantics we've often come to expect in queues. There's no notification or any sort of blocking "get" call.

Amazon's related SNS/Simple Notification Service may be useful to you in this effort. When you've added work to the queue, you can send out a notification to subscribed workers.

See also:

http://aws.amazon.com/sns/

Best practices for using Amazon SQS - Polling the queue

Answer 2

This is (now) possible with Long polling on a SQS queue.

http://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/Query_QueryReceiveMessage.html

Long poll support (integer from 1 to 20) - the duration (in seconds) that the ReceiveMessage action call will wait until a message is in the queue to include in the response, as opposed to returning an empty response if a message is not yet available.

If you do not specify WaitTimeSeconds in the request, the queue attribute ReceiveMessageWaitTimeSeconds is used to determine how long to wait.

Type: Integer from 0 to 20 (seconds)

Default: The ReceiveMessageWaitTimeSeconds of the queue.