AWS Lambda's Python runtime behaves differently from local

[limanjun99]

This issue was first discovered in this PR. The executor lambda was found to behave differently than in local testing, causing errors.

Consider the following testcase (which is already one of the unit tests):

{
    "code": dedent(
        """\
        a = 1
        b = int(input())
        c = int(input())
        d = a + b + c
        print(f'Value of d is {d}')"""
    ),
    "input": dedent(
        """\
        2
        3
        Extra input is ignored"""
    ),
}

It runs fine locally, but when deployed to AWS lambda and we manually run an invocation, we get this response instead:

{
    "executed": true,
    "data": [
        {
            "line_number": 1,
            "local_variable_changes": {
                "a": {
                    "type": "int",
                    "value": 1
                }
            },
            "global_variable_changes": {},
            "function_scope": []
        }
    ],
    "output": "Value of d is 6\n"
}

Looking at the logs, we see that at some point in code execution, we enter a frame with the name awslambdaric.bootstrap, which highly suggests that Lambda is doing something that causes our code to error out.

TODO

• In the future, it would be good to add in a few integration tests as well, since this issue has shown that unit tests alone are not sufficient.
• Figure out why this is happening (and why it hasn't happened till now, since other branches were working fine) and fix it. Might need to look into some kind of sandbox or docker.

[limanjun99]

Not entirely sure why we did not encounter this issue before. The fix for now is to ignore frames where the __name__ in frame globals is awslambdaric.bootstrap, by passing it to the skip parameter when initing a bdb instance. This fix should be sufficient if this is a one-time issue. If this occurs again with multiple other module names, it might be worth the effort to look into sandboxing/docker.

Another issue will be opened to look into adding integration tests in the future.