Lambda 可以从直接调用和 SNS 消息中获取 arguments

Question

Is it possible to construct a Lambda handler such that it will be able to get its arguments from either SNS, or via direct invocation?
In other words, the same Lambda can be invoked either explicitly or via subscription to SNS topic.

Purpose is to have a Lambda that is usually triggered via SNS 90% of the time, but also allow for manual invocation via Console or web API.

It looks like this may be possible via something like

def lambda_handler(event, context):
   args = parse_sns_event(event) if 'Records' in event else event

Assuming that 'Records' is the top-level key in the Lambda SNS event , and that 'Records' is not the name of one of the expected arguments.

Is there a better way to do this? (Short of having two Lambdas - one main worker plus another to receive the SNS message and invoke the other)

Answer 1

Your idea for checking for 'Records' is a good one. When you invoke manually you can pass whatever payload you like so as long as it doesn't include 'Records' then you've got your decision point.

Example:

def handler(event, context):
    if 'Records' in event:
        # Handle SNS trigger
    else:
        # Handle manual trigger

You can pass a payload that you define via the AWS CLI:

aws lambda invoke --function-name your-lambda-function --payload '{"Manual":"yes"}'

Answer 2

What I have done in the past is created a service class that has all the logic

ie LoginService takes in all the params it needs only

Then created 2 functions and I thought of them as controller endpoints Those endpoints all they do is get the params validate them then send them to the service

If called the wrong way the validation would tell the caller

I hope this helps.