feat(logger): add thread safe logging keys

[SimonBFrank]

Issue number: #991

Summary

Changes

• New logger methods:
  • append_thread_local_keys : add key to thread-local ContextVar
  • get_current_thread_keys: get all keys from thread-local ContextVar
  • remove_thread_local_keys: remove list of keys from thread-local ContextVar
  • clear_thread_local_keys: remove all keys from thread-local ContextVar
• Add new logic to_extract_log_keys method to handle error when an additional logging key's value is not a string and the name conflicts with a reserved keys
• clear_state in inject_lambda_context also clears thread-local keys

User experience

Before:

import concurrent.futures

from aws_lambda_powertools import Logger

logger = Logger(service="payment")


def process_payments(payment_id):
    logger.info("Start processing payment", extra={"payment_id": payment_id})
    ...
    logger.info("End processing payment", extra={"payment_id": payment_id})


with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    futures = [executor.submit(process_payments, payment_id) for payment_id in range(10)]
    for future in concurrent.futures.as_completed(futures):
        future.result()

After:

import concurrent.futures

from aws_lambda_powertools import Logger

logger = Logger(service="payment")


def process_payments(payment_id):
    logger.clear_thread_local_keys()
    logger.append_thread_local_keys(payment_id=payment_id)
    logger.info("Start processing payment")
    ...
    logger.info("End processing payment")


with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    futures = [executor.submit(process_payments, payment_id) for payment_id in range(10)]
    for future in concurrent.futures.as_completed(futures):
        future.result()

Checklist

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

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

Is this a breaking change?: No, existing functionality isn't broken.

RFC issue number:

Checklist:

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

Acknowledgment

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