Discussion on: AWS Lambda SQS events with Serverless Framework

[Pedro Rodrigues]

Do I have to delete the message after receiving and processing?

Like:

var params = {
QueueUrl: 'STRING_VALUE', /* required /
ReceiptHandle: 'STRING_VALUE' / required */
};

sqs.deleteMessage(params, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data); // successful response
});

[Marcin Piczkowski]

Hi Pedro, I was confused at the beginning too, because this was the way to handle messages before SQS events were supported in Lambda when you had to poll the queue yourself.

It is not needed anymore and explained in AWS documentation (docs.aws.amazon.com/lambda/latest/...)

Lambda takes care of:
 - Automatically retrieving messages and directing them to the target Lambda function.
 - Deleting them once your Lambda function successfully completes.

What is important is the "successfully completes", because if the Lambda fails the message will remain in the queue and will be processed again, so you need to handle exceptions carefully.

You can e.g. surround lambda in try-catch clause and do not let Lambda fail because of wrong message or configure dead-letter queues where failed messages will be redirected automatically after Lambda fails. Then you can have e.g. separate lambda for dead-letter queues to handle such messages.

I'm planning to write more about Lambda error handling soon.