How do I fail a specific SQS message in a batch from a Lambda?

Question

I have a Lambda with an SQS trigger. When it gets hit, a batch of records from SQS comes in (usually about 10 at a time, I think). If I return a failed status code from the handler, all 10 messages will be retried. If I return a success code, they'll all be removed from the queue. What if 1 out of those 10 messages failed and I want to retry just that one?

exports.handler = async (event) => {

    for(const e of event.Records){
        try {
            let body = JSON.parse(e.body);
            // do things
        }
        catch(e){
            // one message failed, i want it to be retried
        }        
    }

    // returning this causes ALL messages in 
    // this batch to be removed from the queue
    return {
        statusCode: 200,
        body: 'Finished.'
    };
};

Do I have to manually re-add that ones message back to the queue? Or can I return a status from my handler that indicates that one message failed and should be retried?

Answer 1

Yes you have to manually re-add the failed messages back to the queue.

What I suggest doing is setting up a fail count, so that if all messages failed you can simply return a failed status for all messages, otherwise if the fail count is < 10 then you can individually send back the failed messages to the queue.