Using a Dead Letter Queue for AWS Lambda Errors

Question

I have attempted to follow the documentation about setting up an SQS Dead Letter Queue for my Lambda on AWS but I can't seem to get the errors to pass through to it.

I have a Lambda on eu-west-2

exports.handler = async (event) => {
    if (event.desire === 'error') {
        throw new Error('dutifully throw an error');
    }
    
    const response = {
        statusCode: 200,
        body: JSON.stringify('Complete the lambda!'),
    };
    return response;
};

with asynchronous invocation set to my sqs queue test-dlq

I've added the following into the role:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "",
            "Effect": "Allow",
            "Action": "sqs:*",
            "Resource": "arn:aws:sqs:eu-west-2:123456789:test-dlq"
        }
    ]
}

(I've previously had this set to "Action": "sqs:SendMessage" but have made it more permissive for brevity)

And I've setup my SQS Queue to receive the messages:

My test case payload is:

{
    "desire": "error"
}

which causes the lambda to error and add the error to the CloudWatch log but doesn't pass to the DLQ.

Do I need to do anything to route the errors to the Queue or have I misconfigured this please?

Just using the test button at the top right of the lambda function page in the console. I've also tried using the following on the command line: aws lambda invoke --function-name testFunction --payload '{"desire":"error"}' /tmp/out.json — obie

Marcin Marcin · Accepted Answer · 2020-11-05T22:46:52

The reason why your DLQ does not work is because using Test button or invoking function using:

aws lambda invoke --function-name testFunction --payload '{"desire":"error"}' /tmp/out.json

result in synchronous invocations, rather then asynchronous ones.

To invoke your function asynchronously, you have to use Event type in the CLI:

aws lambda invoke --function-name testFunction --invocation-type Event --payload '{"desire":"error"}' /tmp/out.json

Using a Dead Letter Queue for AWS Lambda Errors

1 Answers