logger

This module provides logging utilities

close_logger(logger)

Close all handlers associated to a logging.Logger object

Parameters:

Name	Type	Description	Default
logger	Logger	The actual logger	required

Source code in fractal_server/logger.py

def close_logger(logger: logging.Logger) -> None:
    """
    Close all handlers associated to a `logging.Logger` object

    Arguments:
        logger: The actual logger
    """
    for handle in logger.handlers:
        handle.close()

config_uvicorn_loggers()

Change the formatter for the uvicorn access/error loggers.

This is similar to https://stackoverflow.com/a/68864979/19085332. See also https://github.com/tiangolo/fastapi/issues/1508.

This function is meant to work in two scenarios:

1. The most relevant case is for a gunicorn startup command, with --access-logfile and --error-logfile options set.
2. The case of fractalctl start (directly calling uvicorn).

Because of the second use case, we need to check whether uvicorn loggers already have a handler. If not, we skip the formatting.

Source code in fractal_server/logger.py

def config_uvicorn_loggers():
    """
    Change the formatter for the uvicorn access/error loggers.

    This is similar to https://stackoverflow.com/a/68864979/19085332. See also
    https://github.com/tiangolo/fastapi/issues/1508.

    This function is meant to work in two scenarios:

    1. The most relevant case is for a `gunicorn` startup command, with
       `--access-logfile` and `--error-logfile` options set.
    2. The case of `fractalctl start` (directly calling `uvicorn`).

    Because of the second use case, we need to check whether uvicorn loggers
    already have a handler. If not, we skip the formatting.
    """

    access_logger = logging.getLogger("uvicorn.access")
    if len(access_logger.handlers) > 0:
        access_logger.handlers[0].setFormatter(LOG_FORMATTER)

    error_logger = logging.getLogger("uvicorn.error")
    if len(error_logger.handlers) > 0:
        error_logger.handlers[0].setFormatter(LOG_FORMATTER)

get_logger(logger_name=None)

Wrap the logging.getLogger function.

The typical use case for this function is to retrieve a logger that was already defined, as in the following example:

def function1(logger_name):
    logger = get_logger(logger_name)
    logger.info("Info from function1")

def funtion2():
    logger_name = "my_logger"
    logger = set_logger(logger_name)
    logger.info("Info from function2")
    function1(logger_name)
    close_logger(logger)

Parameters:

Name	Type	Description	Default
logger_name	Optional[str]	Name of logger	None

Returns: Logger with name logger_name

Source code in fractal_server/logger.py

def get_logger(logger_name: Optional[str] = None) -> logging.Logger:
    """
    Wrap the
    [`logging.getLogger`](https://docs.python.org/3/library/logging.html#logging.getLogger)
    function.

    The typical use case for this function is to retrieve a logger that was
    already defined, as in the following example:
    ```python
    def function1(logger_name):
        logger = get_logger(logger_name)
        logger.info("Info from function1")

    def funtion2():
        logger_name = "my_logger"
        logger = set_logger(logger_name)
        logger.info("Info from function2")
        function1(logger_name)
        close_logger(logger)
    ```

    Arguments:
        logger_name: Name of logger
    Returns:
        Logger with name `logger_name`
    """
    return logging.getLogger(logger_name)

reset_logger_handlers(logger)

Close and remove all handlers associated to a logging.Logger object

Parameters:

Name	Type	Description	Default
logger	Logger	The actual logger	required

Source code in fractal_server/logger.py

def reset_logger_handlers(logger: logging.Logger) -> None:
    """
    Close and remove all handlers associated to a `logging.Logger` object

    Arguments:
        logger: The actual logger
    """
    close_logger(logger)
    logger.handlers.clear()

set_logger(logger_name, *, log_file_path=None)

Set up a fractal-server logger

The logger (a logging.Logger object) will have the following properties:

• The attribute Logger.propagate set to False;
• One and only one logging.StreamHandler handler, with severity level set to FRACTAL_LOGGING_LEVEL and formatter set as in the logger.LOG_FORMAT variable from the current module;
• One or many logging.FileHandler handlers, including one pointint to log_file_path (if set); all these handlers have severity level set to logging.DEBUG.

Parameters:

Name	Type	Description	Default
logger_name	str	The identifier of the logger.	required
log_file_path	Optional[Union[str, Path]]	Path to the log file.	None

Returns:

Name	Type	Description
logger	Logger	The logger, as configured by the arguments.

Source code in fractal_server/logger.py

def set_logger(
    logger_name: str,
    *,
    log_file_path: Optional[Union[str, Path]] = None,
) -> logging.Logger:
    """
    Set up a `fractal-server` logger

    The logger (a `logging.Logger` object) will have the following properties:

    * The attribute `Logger.propagate` set to `False`;
    * One and only one `logging.StreamHandler` handler, with severity level set
    to `FRACTAL_LOGGING_LEVEL` and formatter set as in the `logger.LOG_FORMAT`
    variable from the current module;
    * One or many `logging.FileHandler` handlers, including one pointint to
    `log_file_path` (if set); all these handlers have severity level set to
    `logging.DEBUG`.

    Args:
        logger_name: The identifier of the logger.
        log_file_path: Path to the log file.

    Returns:
        logger: The logger, as configured by the arguments.
    """

    logger = logging.getLogger(logger_name)
    logger.propagate = False
    logger.setLevel(logging.DEBUG)

    current_stream_handlers = [
        handler
        for handler in logger.handlers
        if isinstance(handler, logging.StreamHandler)
    ]

    if not current_stream_handlers:
        stream_handler = logging.StreamHandler()
        settings = Inject(get_settings)
        stream_handler.setLevel(settings.FRACTAL_LOGGING_LEVEL)
        stream_handler.setFormatter(LOG_FORMATTER)
        logger.addHandler(stream_handler)

    if log_file_path is not None:
        file_handler = logging.FileHandler(log_file_path, mode="a")
        file_handler.setLevel(logging.DEBUG)
        file_handler.setFormatter(LOG_FORMATTER)
        file_handler.setFormatter(LOG_FORMATTER)
        logger.addHandler(file_handler)
        current_file_handlers = [
            handler
            for handler in logger.handlers
            if isinstance(handler, logging.FileHandler)
        ]
        if len(current_file_handlers) > 1:
            logger.warning(f"Logger {logger_name} has multiple file handlers.")

    return logger