feat: support extra parameter in Logger messages

[heitorlessa]

Issue #, if available: #253

Description of changes:

This PR adds support for extra parameter when logging messages across all levels. Any key/value added using extra parameter will be at the root level of the structured log.

Before this PR, all fields added in extra parameter are discarded when structuring logs.

UX

Add request_id field while logging a message

logger = Logger(service="payment")

fields = { "request_id": "1123" }
logger.info("Hello", extra=fields)

{
    "level": "INFO",
    "location": "<module>:5",
    "message": "Hello",
    "timestamp": "2021-01-12 14:08:12,357",
    "service": "payment",
    "sampling_rate": 0.0,
    "request_id": "1123"
}

FAQ

Q: What's the difference between structure_log and extra after this PR?

Keys added with structure_log will persist across multiple log messages while keys added via extra will only be available in a given log message operation.

Example - Persisting payment_id not request_id

from aws_lambda_powertools import Logger

logger = Logger(service="payment")
logger.structure_logs(append=True, payment_id="123456789")

try:
    booking_id = book_flight()
    logger.info("Flight booked successfully", extra={ "booking_id": booking_id})
except BookingReservationError:
    ...

logger.info("goodbye")

Note that payment_id remains in both log messages while booking_id is only available in the first message.

{
    "level": "INFO",
    "location": "<module>:5",
    "message": "Flight booked successfully",
    "timestamp": "2021-01-12 14:09:10,859",
    "service": "payment",
    "sampling_rate": 0.0,
    "payment_id": "123456789",
    "booking_id": "75edbad0-0857-4fc9-b547-6180e2f7959b"
},
{
    "level": "INFO",
    "location": "<module>:6",
    "message": "goodbye",
    "timestamp": "2021-01-12 14:09:10,860",
    "service": "payment",
    "sampling_rate": 0.0,
    "payment_id": "123456789"
}

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

RFC issue #:

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

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[heitorlessa]

customer approvals: #253 (comment)