What is a good practice to achieve the "Exactly-once delivery" behavior with Amazon SQS?

Question

Q: How many times will I receive each message?

Amazon SQS is engineered to provide “at least once” delivery of all messages in its queues. Although most of the time each message will be delivered to your application exactly once, you should design your system so that processing a message more than once does not create any errors or inconsistencies.

Is there any good practice to achieve the exactly-once delivery?

I was thinking about using the DynamoDB “Conditional Writes” as distributed locking mechanism but... any better idea?

Some reference to this topic:

The following article sums up the solutions (Idempotent vs using locks) pretty well linkedin.com/pulse/… — Ben Yitzhaki

Jeff Jeff · Accepted Answer · 2012-11-21T09:25:50

The best solution really depends on exactly how critical it is that you not perform the action suggested in the message more than once. For some actions such as deleting a file or resizing an image it doesn't really matter if it happens twice, so it is fine to do nothing. When it is more critical to not do the work a second time I use an identifier for each message (generated by the sender) and the receiver tracks dups by marking the ids as seen in memchachd. Fine for many things, but probably not if life or money depends on it, especially if there a multiple consumers.

Conditional writes sound like a clever solution, but it has me wondering if perhaps AWS isn't such a great solution for your problem if you need a bullet proof exactly-once solution.

What is a good practice to achieve the "Exactly-once delivery" behavior with Amazon SQS?

3 Answers