AWS Lambda + SQS (Java)。 Lambda 已成功完成工作，但未从 SQS 中删除消息。 是否应再次发送此消息以进行处理？

Question

I faced with such aws sqs behavior.

I have lambda is triggered by api gateway. In this lambda in some cases i need to reprocess incoming request. So in such cases i send incoming request as message to sqs with delay (30s). In sqs "Default Visibility Timeout" set up to 1 min and and linked dlq queue.

In lambda i have next logic:

1. When i get request by api gateway and my lambda decides to reprocess it, then it first time sends message to sqs for reprocessing. Them my lambda gets message back in 30s. Ok.

2. But when during this reprocessing i need to reprocess it again, my lambda does nothing and simply finishes. Because in aws docs says that for the message acknowledge in sqs i need to send the delete request. Lambda doesn't send it. I thought it should work. But not.

3. Then my lambda doesn't get this message again and also i don't see the message in the queue.

4. But when i throw the exception instead of simply finish work, lambda gets message again.

Is this really need to throw the exception for getting message from sqs to lambda again instead of simply not send the delete request for message.

Thank you!

Answer 1

As you wrote docs for SQS says messages need to be deleted from the queue to be considered as handled. Otherwise they are considered not handled and SQS will try to deliver them again until configured limit is reached.

If AWS docs says something and AWS works respectively, then there is no need to ask if AWS docs are really really correct.