feat(logger-utils): preserve log level for discovered third-party top-level loggers

aws_lambda_powertools/logging/utils.py

@@ -9,17 +9,21 @@
 def copy_config_to_registered_loggers(
     source_logger: Logger,
     log_level: Optional[Union[int, str]] = None,
+    ignore_log_level=False,
     exclude: Optional[Set[str]] = None,
     include: Optional[Set[str]] = None,
 ) -> None:
     """Copies source Logger level and handler to all registered loggers for consistent formatting.
 
     Parameters
     ----------
+    ignore_log_level
     source_logger : Logger
         Powertools for AWS Lambda (Python) Logger to copy configuration from
     log_level : Union[int, str], optional
         Logging level to set to registered loggers, by default uses source_logger logging level
+    ignore_log_level: bool
+        Whether to not touch log levels for discovered loggers. log_level param is disregarded when this is set.
     include : Optional[Set[str]], optional
         List of logger names to include, by default all registered loggers are included
     exclude : Optional[Set[str]], optional
@@ -54,7 +58,7 @@ def copy_config_to_registered_loggers(
 
     registered_loggers = _find_registered_loggers(source_logger, loggers, filter_func)
     for logger in registered_loggers:
-        _configure_logger(source_logger, logger, level)
+        _configure_logger(source_logger=source_logger, logger=logger, level=level, ignore_log_level=ignore_log_level)
 
 
 def _include_registered_loggers_filter(loggers: Set[str]):
@@ -78,13 +82,21 @@ def _find_registered_loggers(
     return root_loggers
 
 
-def _configure_logger(source_logger: Logger, logger: logging.Logger, level: Union[int, str]) -> None:
+def _configure_logger(
+    source_logger: Logger,
+    logger: logging.Logger,
+    level: Union[int, str],
+    ignore_log_level: bool = False,
+) -> None:
+    # customers may not want to copy the same log level from Logger to discovered loggers
+    if not ignore_log_level:
+        logger.setLevel(level)
+        source_logger.debug(f"Logger {logger} reconfigured to use logging level {level}")
+
     logger.handlers = []
-    logger.setLevel(level)
     logger.propagate = False  # ensure we don't propagate logs to existing loggers, #1073
     source_logger.append_keys(name="%(name)s")  # include logger name, see #1267
 
-    source_logger.debug(f"Logger {logger} reconfigured to use logging level {level}")
     for source_handler in source_logger.handlers:
         logger.addHandler(source_handler)
         source_logger.debug(f"Logger {logger} reconfigured to use {source_handler}")

docs/core/logger.md

@@ -811,10 +811,11 @@ for the given name and level to the logging module. By default, this logs all bo
 
 You can copy the Logger setup to all or sub-sets of registered external loggers. Use the `copy_config_to_registered_logger` method to do this.
 
-???+ tip
-    To help differentiate between loggers, we include the standard logger `name` attribute for all loggers we copied configuration to.
+!!! tip "We include the logger `name` attribute for all loggers we copied configuration to help you differentiate them."
+
+By default all registered loggers will be modified. You can change this behavior by providing `include` and `exclude` attributes.
 
-By default all registered loggers will be modified. You can change this behavior by providing `include` and `exclude` attributes. You can also provide optional `log_level` attribute external loggers will be configured with.
+You can also provide optional `log_level` attribute external top-level loggers will be configured with, by default it'll use the source logger log level. You can opt-out by using `ignore_log_level=True` parameter.
 
 ```python hl_lines="10" title="Cloning Logger config to all other registered standard loggers"
 ---8<-- "examples/logger/src/cloning_logger_config.py"

tests/functional/test_logger_utils.py

@@ -131,8 +131,8 @@ def test_copy_config_to_ext_loggers_include_exclude(stdout, logger, log_level):
     # AND external logger_1 is also in EXCLUDE list
     utils.copy_config_to_registered_loggers(
         source_logger=powertools_logger,
-        include={logger_1.name, logger_2.name},
         exclude={logger_1.name},
+        include={logger_1.name, logger_2.name},
     )
     msg = "test message3"
     logger_2.info(msg)
@@ -175,8 +175,8 @@ def test_copy_config_to_ext_loggers_custom_log_level(stdout, logger, log_level,
     # AND external logger used with custom log_level
     utils.copy_config_to_registered_loggers(
         source_logger=powertools_logger,
-        include={logger.name},
         log_level=level_to_set,
+        include={logger.name},
     )
     msg = "test message4"
     logger.warning(msg)
@@ -263,7 +263,7 @@ def test_copy_config_to_ext_loggers_no_duplicate_logs(stdout, logger, log_level)
 
     # WHEN configuration copied from Powertools for AWS Lambda (Python) logger
     # AND external logger used with custom log_level
-    utils.copy_config_to_registered_loggers(source_logger=powertools_logger, include={logger.name}, log_level=level)
+    utils.copy_config_to_registered_loggers(source_logger=powertools_logger, log_level=level, include={logger.name})
     msg = "test message4"
     logger.warning(msg)
 
@@ -294,3 +294,22 @@ def test_logger_name_is_included_during_copy(stdout, logger, log_level):
     assert logger1_log["name"] == logger_1.name
     assert logger2_log["name"] == logger_2.name
     assert pt_log["name"] == powertools_logger.name
+
+
+def test_copy_config_to_ext_loggers_but_preserve_log_levels(stdout, logger, log_level):
+    # GIVEN two external loggers and Powertools for AWS Lambda (Python) logger initialized
+    third_party_log_level = logging.CRITICAL
+
+    logger_1 = logger()
+    logger_2 = logger()
+    logger_1.setLevel(third_party_log_level)
+    logger_2.setLevel(third_party_log_level)
+
+    powertools_logger = Logger(service=service_name(), stream=stdout)
+
+    # WHEN configuration copied from Powertools for AWS Lambda (Python) logger to ALL external loggers
+    utils.copy_config_to_registered_loggers(source_logger=powertools_logger, ignore_log_level=True)
+
+    # THEN external loggers log levels should be preserved
+    assert logger_1.level != powertools_logger.log_level
+    assert logger_2.level != powertools_logger.log_level