Docs: The output of the bring_your_own_formatter_from_scratch.py example does not match the documentation.

[wchaws]

What were you searching in the docs?

In https://docs.powertools.aws.dev/lambda/python/latest/core/logger/#bring-your-own-formatter doc, the output is

{
    "event": "Collecting payment",
    "timestamp": "2021-05-03 11:47:12,494",
    "my_default_key": "test",
    "cold_start": true,
    "function_name": "test",
    "function_memory_size": 128,
    "function_arn": "arn:aws:lambda:eu-west-1:12345678910:function:test",
    "function_request_id": "52fdfc07-2182-154f-163f-5f0f9a621d72"
}

But actually, in my lambda environment the output is

{"event": "Collecting payment", "timestamp": null, "my_default_key": "test", "level": null, "location": null, "message": null, "service": "payment", "sampling_rate": null, "cold_start": true, "function_name": "PowertoolsTest", "function_memory_size": "128", "function_arn": "arn:aws:lambda:us-west-2:*******:function:PowertoolsTest", "function_request_id": "67a57243-9819-4637-af53-8b2116bd5dbd"}

timestamp and log level are null.

My lambda layer version is arn:aws:lambda:us-west-2:017000801446:layer:AWSLambdaPowertoolsPythonV2:48

Is this related to an existing documentation section?

No response

How can we improve?

Fix the wrong document

Got a suggestion in mind?

No response

Acknowledgment

• I understand the final update might be different from my proposed suggestion, or refused.

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out the #python channel on our Powertools for AWS Lambda Discord: Invite link

[heitorlessa]

Thank you @wchaws for taking the time to report this - we'll look into it this afternoon.

[heitorlessa]

I couldn't replicate in Lambda using the same version, would you be able to share how does your custom formatter look like?

I've just used the same custom formatter code and invoke a Lambda function via API Gateway to be sure.

---

Code used and CloudWatch Logs

Code snippet

from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import APIGatewayRestResolver
from aws_lambda_powertools.logging.formatter import LambdaPowertoolsFormatter
from aws_lambda_powertools.logging.types import LogRecord


class CustomFormatter(LambdaPowertoolsFormatter):
    def serialize(self, log: LogRecord) -> str:
        """Serialize final structured log dict to JSON str"""
        # in this example, log["message"] is a required field
        # but we want to remap to "event" and delete "message", hence mypy ignore checks
        log["event"] = log.pop("message")  # type: ignore[typeddict-unknown-key,misc]
        return self.json_serializer(log)


app = APIGatewayRestResolver()
logger = Logger(logger_formatter=CustomFormatter())


@app.get("/todos")
def get_todos():
    logger.info("Timestamp and level shouldn't be null")
    return {
        "issue": "https://github.com/aws-powertools/powertools-lambda-python/issues/3378"
    }


@logger.inject_lambda_context
def lambda_handler(event: dict, context):
    return app.resolve(event, context)

[heitorlessa]

Closing; please feel free to reopen if I missed anything when trying to reproduce.

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