Amazon SNS delivery retry policies for SQS

Question

We're implementing AWS fanout pattern using SNS topic with multiple SQS queue subscribers. I was wondering what would happen if I successfully publish a message on a SNS topic but it fails (for some reason) to forward it to the queue(s). Will SNS retry and if so, is there a way to control this.

I found this page http://docs.aws.amazon.com/sns/latest/dg/DeliveryPolicies.html that talks about configuring retry policies for SNS HTTP/HTTPS endpoints but there's nothing on SQS.

Answer 1

Practically, AWS guarantees the delivery of messages to SQS from SNS. Since the question quotes as below, I want to point out a reason where delivery to SQS can fail.

I was wondering what would happen if I successfully publish a message on a SNS topic but it fails (for some reason) to forward it to the queue(s).

This can happen only if the SQS we are pointing to, has been deleted (or is being deleted) by some process. As taken from SNS Faqs, if the SQS is unavailable, it will retry for a number of tries until the message is discarded.

SQS: If a SQS queue is not available, SNS will retry 10 times immediately, then 100,000 times every 20 seconds for a total of 100,010 attempts over more than 23 days before the message is discarded from SNS.

This was pointed out by @grigori in a comment.

Answer 2

I'm a member of the SNS development team. For the SQS deliveries, SNS will retry thousands of times before giving up. Except in the case of catastrophic multi-day outages, message deliveries to SQS are guaranteed.