feat(logger): add method to return currently configured keys

aws_lambda_powertools/logging/formatter.py

@@ -48,6 +48,9 @@ class BasePowertoolsFormatter(logging.Formatter, metaclass=ABCMeta):
     def append_keys(self, **additional_keys) -> None:
         raise NotImplementedError()
 
+    def get_current_keys(self) -> Dict[str, Any]:
+        return {}
+
     def remove_keys(self, keys: Iterable[str]) -> None:
         raise NotImplementedError()
 
@@ -231,6 +234,9 @@ def formatTime(self, record: logging.LogRecord, datefmt: Optional[str] = None) -
     def append_keys(self, **additional_keys) -> None:
         self.log_format.update(additional_keys)
 
+    def get_current_keys(self) -> Dict[str, Any]:
+        return self.log_format
+
     def remove_keys(self, keys: Iterable[str]) -> None:
         for key in keys:
             self.log_format.pop(key, None)

aws_lambda_powertools/logging/logger.py

@@ -583,6 +583,12 @@ def debug(
     def append_keys(self, **additional_keys: object) -> None:
         self.registered_formatter.append_keys(**additional_keys)
 
+    def get_current_keys(self) -> Dict[str, Any]:
+        if isinstance(self.registered_formatter, LambdaPowertoolsFormatter):
+            return self.registered_formatter.get_current_keys()
+
+        return {}
+
     def remove_keys(self, keys: Iterable[str]) -> None:
         self.registered_formatter.remove_keys(keys)
 

docs/core/logger.md

@@ -274,6 +274,16 @@ Logger is commonly initialized in the global scope. Due to [Lambda Execution Con
     --8<-- "examples/logger/src/clear_state_event_two.json"
     ```
 
+### Accessing currently configured keys
+
+You can view all currently configured keys from the Logger state using the `get_current_keys()` method. This method is useful when you need to avoid overwriting keys that are already configured.
+
+=== "get_current_keys.py"
+
+    ```python hl_lines="4 11"
+    --8<-- "examples/logger/src/get_current_keys.py"
+    ```
+
 ### Log levels
 
 The default log level is `INFO`. It can be set using the `level` constructor option, `setLevel()` method or by using the `POWERTOOLS_LOG_LEVEL` environment variable.
@@ -732,7 +742,7 @@ The `log` argument is the final log record containing [our standard keys](#stand
 For exceptional cases where you want to completely replace our formatter logic, you can subclass `BasePowertoolsFormatter`.
 
 ???+ warning
-    You will need to implement `append_keys`, `clear_state`, override `format`, and optionally `remove_keys` to keep the same feature set Powertools for AWS Lambda (Python) Logger provides. This also means keeping state of logging keys added.
+    You will need to implement `append_keys`, `clear_state`, override `format`, and optionally `get_current_keys`, and `remove_keys` to keep the same feature set Powertools for AWS Lambda (Python) Logger provides. This also means tracking the added logging keys.
 
 === "bring_your_own_formatter_from_scratch.py"
 

examples/logger/src/bring_your_own_formatter_from_scratch.py

@@ -1,6 +1,6 @@
 import json
 import logging
-from typing import Iterable, List, Optional
+from typing import Any, Dict, Iterable, List, Optional
 
 from aws_lambda_powertools import Logger
 from aws_lambda_powertools.logging.formatter import BasePowertoolsFormatter
@@ -16,6 +16,9 @@ def append_keys(self, **additional_keys):
         # also used by `inject_lambda_context` decorator
         self.log_format.update(additional_keys)
 
+    def current_keys(self) -> Dict[str, Any]:
+        return self.log_format
+
     def remove_keys(self, keys: Iterable[str]):
         for key in keys:
             self.log_format.pop(key, None)

examples/logger/src/get_current_keys.py

@@ -0,0 +1,14 @@
+from aws_lambda_powertools import Logger
+from aws_lambda_powertools.utilities.typing import LambdaContext
+
+logger = Logger()
+
+
+@logger.inject_lambda_context
+def lambda_handler(event: dict, context: LambdaContext) -> str:
+    logger.info("Collecting payment")
+
+    if "order" not in logger.get_current_keys():
+        logger.append_keys(order=event.get("order"))
+
+    return "hello world"

tests/functional/test_logger.py

@@ -9,10 +9,9 @@
 import string
 import sys
 import warnings
-from ast import Dict
 from collections import namedtuple
 from datetime import datetime, timezone
-from typing import Any, Callable, Iterable, List, Optional, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, Union
 
 import pytest
 
@@ -606,6 +605,45 @@ def test_logger_append_remove_keys(stdout, service_name):
     assert (extra_keys.items() <= keys_removed_log.items()) is False
 
 
+def test_logger_append_and_show_current_keys(stdout, service_name):
+    # GIVEN a Logger is initialized
+    logger = Logger(service=service_name, stream=stdout)
+    extra_keys = {"request_id": "id", "context": "value"}
+
+    # WHEN keys are updated
+    logger.append_keys(**extra_keys)
+
+    # THEN appended keys must be present in logger
+    current_keys = logger.get_current_keys()
+    assert "request_id" in current_keys
+    assert "context" in current_keys
+
+
+def test_logger_formatter_without_get_current_keys_method(stdout, service_name):
+    class CustomFormatter(BasePowertoolsFormatter):
+        def append_keys(self, **additional_keys):
+            # Fake method
+            pass
+
+        def clear_state(self) -> None:
+            # Fake method
+            pass
+
+    custom_formater = CustomFormatter()
+
+    # GIVEN a Logger is initialized with a Logger Formatter from scratch
+
+    logger = Logger(service=service_name, stream=stdout, logger_formatter=custom_formater)
+    extra_keys = {"request_id": "id", "context": "value"}
+
+    # WHEN keys are updated
+    logger.append_keys(**extra_keys)
+
+    # THEN the appended keys will not persist
+    # unless the customer implements the required methods and persists the log_format
+    assert logger.get_current_keys() == {}
+
+
 def test_logger_custom_formatter(stdout, service_name, lambda_context):
     class CustomFormatter(BasePowertoolsFormatter):
         custom_format = {}