feat(buffer-handler): add buffering support for external loggers

[acascell]

Issue number: closes #7918

Summary

This PR implements log buffering support for external libraries when using AWS Lambda Powertools Logger with buffering enabled.

Changes

1. New BufferingHandler class (aws_lambda_powertools/logging/buffer/handler.py):

   • Custom logging handler that intercepts logs from external libraries extending logging.Handler
   • Override and extends emit() method delegating to the source Logger's _add_log_record_to_buffer() function
   • Shares the same buffer cache and tracer_id as the Powertools Logger
   • Ensures external library logs are buffered and flushed together with application logs

2. Enhanced copy_config_to_registered_loggers() function (aws_lambda_powertools/logging/utils.py):

   • Added new include_buffering parameter (default: False)
   • Maintains backward compatibility - existing behavior unchanged when parameter is False

3. Updated configuration logic (-):

   • adds BufferingHandler on include_buffering flag

4. Included unit and functional tests

• tests/functional/logger/required_dependencies/test_logger_utils.py
• tests/unit/logger/required_dependencies/test_logger_buffer_handler.py

User Experience

Before this change:
When using Logger with buffering enabled, external library logs (botocore, mangum, etc.) were NOT buffered - they appeared immediately in CloudWatch, defeating the purpose of buffering:

from aws_lambda_powertools import Logger
from aws_lambda_powertools.logging import utils
from aws_lambda_powertools.logging.config import LoggerBufferConfig

# Enable buffering on Powertools Logger
buffer_config = LoggerBufferConfig(
    max_bytes=20480,
    buffer_at_verbosity="DEBUG",
    flush_on_error_log=True
)
LOGGER = Logger(service="payment", buffer_config=buffer_config)

# Configure external loggers
utils.copy_config_to_registered_loggers(source_logger=LOGGER)

# Get external logger
botocore_logger = logging.getLogger("botocore")

def handler(event, context):
    LOGGER.debug("Processing payment")              # Buffered
    LOGGER.info("Validating request")               # Buffered
    botocore_logger.info("Making API call")         # NOT buffered (appears immediately)
    botocore_logger.debug("Request headers set")    # NOT buffered (appears immediately)
    LOGGER.error("Payment failed")                  # Flushes only LOGGER's logs

Result: External library logs appeared immediately in CloudWatch, while application logs were buffered.

After this change:
External library logs are now buffered alongside application logs when include_buffering=True:

from aws_lambda_powertools import Logger
from aws_lambda_powertools.logging import utils
from aws_lambda_powertools.logging.config import LoggerBufferConfig

# Enable buffering on Powertools Logger
buffer_config = LoggerBufferConfig(
    max_bytes=20480,
    buffer_at_verbosity="DEBUG",
    flush_on_error_log=True
)
LOGGER = Logger(service="payment", buffer_config=buffer_config)

# Configure external loggers WITH buffering
utils.copy_config_to_registered_loggers(
    source_logger=LOGGER,
    include_buffering=True  # Enable buffering for external loggers
)

# Get external logger
botocore_logger = logging.getLogger("botocore")

def handler(event, context):
    LOGGER.debug("Processing payment")              # Buffered
    LOGGER.info("Validating request")               # Buffered
    botocore_logger.info("Making API call")         # Buffered
    botocore_logger.debug("Request headers set")    # Buffered
    LOGGER.error("Payment failed")                  # Flushes ALL logs (app + external)

Result: All logs (application + external libraries) are buffered together and flushed as a unit

---

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

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[boring-cyborg]

Thanks a lot for your first contribution! Please check out our contributing guidelines and don't hesitate to ask whatever you need.
In the meantime, check out the #python channel on our Powertools for AWS Lambda Discord: Invite link

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dreamorosi]

Hi @acascell - thanks for the PR and sorry for the delayed review.

@leandrodamascena will most likely review this next week once he's back.