How to prevent AWS SQS from deleting a message when Lambda function triggered fails to process that message?

Question

I have deployed a AWS Lambda function that triggers when a SQS queue receives a message. The function makes a request to a Rest API and if the response is not Ok the SQS message needs to be processed again.

That's why I need to resend the message to the queue but I would prefer to delete the SQS messages programatically, although I can't find how to configure SQS. I have tried message retention but it seems the trigger event causes the message being deleted anyway.

Other possible options could be back up the message in S3 or persisting it in DynamoDB but I wonder if there's a better option.

Any insights on this question would be very helpful.

Answer 1

From AWS Lambda Retry Behavior - AWS Lambda:

If you configure an Amazon SQS queue as an event source, AWS Lambda will poll a batch of records in the queue and invoke your Lambda function. If the invocation fails or times out, every message in the batch will be returned to the queue, and each will be available for processing once the Visibility Timeout period expires. (Visibility timeouts are a period of time during which Amazon Simple Queue Service prevents other consumers from receiving and processing the message).

Once an invocation successfully processes a batch, each message in that batch will be removed from the queue. When a message is not successfully processed, it is either discarded or if you have configured an Amazon SQS Dead Letter Queue, the failure information will be directed there for you to analyze.

So, it seems (from reading this) that a simple option would be set a high visibility timeout on the queue and then raise an error if the function cannot process the message. This message will remain invisible for the configured timeout period, then would reappear on the queue for processing. If it exceeds the permitted number of retries, it would be deleted or moved to a Dead Letter Queue (if configured).