How to handle timeouts in a python lambda?

Question

I know this has been questioned before, but no real solution was proposed and I was wondering if there any new ways nowadays.

Is there anyway to hook an event using any AWS service to check if a lambda has timed out? I mean it logs into the CloudWatch logs that it timed out so there must be a way.

Specifically in Python because its not so simple to keep checking if its reaching the 20 minute mark as you can with Javascript and other naturally concurrent languages.

Ideally I want to execute a lambda if the python lambda times out, with the same payload the original one received.

Answer 1

Here's an example from cloudformation-custom-resources/lambda/python · GitHub showing how an AWS Lambda function written in Python can realise that it is about to timeout.

(I've edited out the other stuff, here's the relevant bits):

import signal

def handler(event, context):

    # Setup alarm for remaining runtime minus a second
    signal.alarm((context.get_remaining_time_in_millis() / 1000) - 1)

    # Do other stuff
    ...

def timeout_handler(_signal, _frame):
    '''Handle SIGALRM'''
    raise Exception('Time exceeded')

signal.signal(signal.SIGALRM, timeout_handler)