basic config to run a python docker image via AWS Lambda function

January 30, 2024

I have five hours trying to get a Lambda function to successfully return a response, using a Docker image, and failing miserably.

Dockerfile

FROM python:3.9.6-buster
WORKDIR /app
COPY . /app
CMD ["python", "/app/lambda_handler.py"]

Python files
p.py

def c(a1, a1, a1):
    result = {
        "a1": a1,
        "a2": a2,
        "a3": a3,
    }
    return result

lambda_handler.py

import json
from p import c
def lambda_handler(event, context):
    arg1 = event["a1"]
    arg2 = event["a2"]
    arg3 = event["a3"]

    result = classify(arg1, arg2, arg3)

    response = {"statusCode": 200, "body": result}

    return json.dumps(response, indent=4, default=str)

I get an unhelpful error of

{
"errorType": "Runtime.InvalidEntrypoint",
"errorMessage": "RequestId: 330fa2c3-f68b-4225-a53c-96f2409f186d Error: exec: "lambda_function.lambda_handler": executable file not found in $PATH"
}

I have tried:

zipping the files and uploading to the lambda function which works
read this link which suggests using using something like CMD [ "lambda_function.handler" ] so I have set the override CMD to combinations of app.lambda_function.lambda_handler, lambda_function.lambda_handler with and without quotes
I have tried setting the ENTRYPOINT to python, and then trying to point the CMD to /app/lambda_handler
instead of using CMD exclusively using ENTRYPOINT override python, /app/lambda_handler.py

Any help would be most appreciated.

>Solution :

The error appears to be a configuration problem with your AWS Lambda function.

If you check the message it says Error type: Runtime.InvalidEntrypoint ... Error: exec: "lambda_function.lambda_handler"

By default the Entrypoint of AWS Lambda in the console is lambda_function.lambda_handler and according to the documentation this is

.. This function handler name reflects the function name (lambda_handler) and the file where the handler code is stored (lambda_function.py).

In your case your python file is named lambda_handler.py instead of lambda_function.py which is why AWS Lambda fails to find your handler and throws the error InvalidEntrypoint.

Try changing the name of your file to lambda_function.py