feat(logger): accept arbitrary keyword=value for ephemeral metadata

[heitorlessa]

Issue number: #1167

This supersedes PR #1505 as (1) Noah is busy with his day-to-day work priorities, and (2) the actual solution requires a full rewrite of the original PR

Summary

This PR backports the necessary code implemented in CPython 3.8, monkeypatch and adds additional guards to only use the backported code in older Python versions to not impact performance and future improvements.

Changes

Please provide a summary of what's being changed

This change allows customers to pass arbitrary and ephemeral keyword=value arguments in log statements.

It addresses one of the oldest issues and makes it a better UX than extra argument. Both can coexist. This is a backport feature from Python 3.8.

Why did it take us so long?

The reason that this took us so long was that we inject the location key in log, so customers know where a logging statement came from in their code.

{
    "level": "WARNING",
    "location": "warning:465",
    "message": "Testing",
    "timestamp": "2022-10-26 16:22:27,543+0200",
    "service": "payment",
    "request_id": "0c7ff166-3be1-4795-8f0c-b48ca5ce5a95"
}

When using a class like Logger, we need to override all log statement methods. When doing so, it moves the stack frame location, where the location key now points to where the statement was called inside Logger, instead of the customer log statement location.

def warning(msg, *args, **kwargs):...
def info(msg, *args, **kwargs):
    return self._logger.info(msg, *args, **kwargs)  # <--- location would always show up here
....

With this change, the location continues to be precise as we move the stack frame location.

{
    "level": "WARNING",
    "location": "<module>:7",
    "message": "Testing",
    "timestamp": "2022-10-26 15:54:34,945+0200",
    "service": "payment",
    "request_id": "c344d8ca-2697-42b1-ad67-2bed036c550d",
}

User experience

Please share what the user experience looks like before and after this change

BEFORE

from aws_lambda_powertools import Logger

from uuid import uuid4

logger = Logger(service="payment")

logger.warning("Testing", extra={"request_id": f"{uuid4()}"})

AFTER

from aws_lambda_powertools import Logger

from uuid import uuid4

logger = Logger(service="payment")

logger.warning("Testing", request_id=f"{uuid4()}")

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• Meet tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

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[heitorlessa]

Waiting for CI to complete to ensure it works in a fresh Python env, then will refresh Docs.

[heitorlessa]

Need to add co-authorship for Noah before merging (@OGoodness). I'll work on docs now as we've finished peer review due to the complexity of this change.

[heitorlessa]

Docs now in!

[leandrodamascena]

Amazing work @heitorlessa! Thanks for sharing the ideas you had for changing the code this way and make it simple.