Question 201847 in Amazon Web Sevices Question posted in
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Amazon web services – How to prevent a Python AWS Lambda from logging an unhandled exception

How do I prevent a Python 3.8 AWS Lambda from logging an unhandled exception?

We have a Python 3.8 AWS Lambda function that is only invoked directly, not via API Gateway or any other AWS service. We have custom logging that formats it correctly for a third party service to consume.

When this lambda has an exception, we want it to fail. Currently the invocation response is:

{
    "StatusCode": 200,
    "FunctionError": "Unhandled",
    "ExecutedVersion": "$LATEST"
}

And the returned payload is:

{
    "errorMessage": "It broke.",
    "errorType": "BrokeError",
    "stackTrace": [
        "many redacted lines...n"
    ]
}

This is great, except when Python crashes, AWS logs this exception using the default AWS logger (which I suspect is stderr), not our custom one. This disrupts integration with our third party log aggregator.

We can wrap the whole lambda function in a try/except and log it explicitly, but we ideally want the "FunctionError": "Unhandled" in the client response. How can this be caused without triggering an automatic error log?

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2

Answers


  1. 0

    This should allow you guys to respond with HTTP 500 without triggering a crash in the Python runtime.

    import json

def lambda_handler(event, context):
  try:
    # Do work here

    return {
        "statusCode": 200,
        "headers": {
            "Content-Type": "application/json"
        },
        "body": json.dumps({})
    }
  except:
    print("An exception occurred")

    return {
          "statusCode": 500,
          "headers": {
              "Content-Type": "application/json"
          },
          "body": json.dumps({})
    }
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  2. 0

    but we ideally want the "FunctionError": "Unhandled" in the client response

    Then handle the error, and put that message in the response:

    def lambda_handler(event, context):
  try:
    # Your current handler code goes here
  except:
    return {
        "statusCode": 500,
        "headers": {
            "Content-Type": "application/json"
        },
        "body": json.dumps({
            "FunctionError": "Unhandled"
        })
    }
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