Source code for spinningdiskanalyzer.logger

"""Handles setup of the debug log."""

from . import meta

import logging
import logging.handlers
from appdirs import user_log_dir
from pathlib import Path
import sys
import re




def setup():
    """Configures event logging for the application."""

    # Set log granularity on root logger.
    log = logging.getLogger()
    log.setLevel(logging.DEBUG)

    # Suppress noise from certain libraries in the log output.
    mute = ('pyvips', 'PIL', 'matplotlib')
    for package in mute:
        logging.getLogger(package).propagate = False

    # Store log files inside the system's application data folder.
    logs = logs_folder()
    logs.mkdir(exist_ok=True, parents=True)

    # Also log to the console.
    handler = logging.StreamHandler(sys.stdout)
    log.setLevel(logging.DEBUG)
    logging.setLogRecordFactory(timed_records)
    entry = '%(timestamp)s | %(levelname)-8s | %(message)s'
    times = '%Y-%m-%d %H:%M:%S'
    formatter = logging.Formatter(entry, datefmt=times)
    handler.setFormatter(formatter)
    log.addHandler(handler)

    # Rotate out old log entries to separate file once a day.
    handler = logging.handlers.TimedRotatingFileHandler(
        logs/'today.txt', encoding='UTF-8-sig', when='midnight')
    handler.rotation_filename = rotation_filename
    entry = '%(asctime)s | %(levelname)-8s | %(message)s | %(name)s'
    times = '%H:%M:%S'
    formatter = logging.Formatter(entry, datefmt=times)
    handler.setFormatter(formatter)
    log.addHandler(handler)





def logs_folder() -> Path:
    """Returns the folder containing the log files."""
    return Path(user_log_dir(appname=meta.title, appauthor=''))





def rotation_filename(path: Path) -> Path:
    """
    Monkey-patches the logging handler's file renaming mechanism so that,
    on roll-over, log files from previous days get the actual date, and
    only that, as the file name, and have `.txt` as the suffix.

    *Note*: A proper implementation would also have to override the
    `getFilesToDelete()` method. But this here works for our use case
    where we never purge logs. Refer to the [source code][1] for further
    details.

    [1]: https://github.com/python/cpython/blob/master/Lib/logging/handlers.py
    """
    path = Path(path)
    date = re.match(r'\.(\d\d\d\d-\d\d-\d\d)', path.suffix).group(1)
    return path.with_name(f'{date}.txt')



original_records = logging.getLogRecordFactory()




def timed_records(*args, **kwargs) -> logging.LogRecord:
    """
    Adds a relative `timestamp` to the log record attributes.

    Example usage:
    ```
    logging.setLogRecordFactory(timed_records)
    logging.basicConfig(format='[%(timestamp)s] %(message)s')
    ```
    """
    record = original_records(*args, **kwargs)
    (minutes, seconds) = divmod(record.relativeCreated/1000, 60)
    record.timestamp = f'{minutes:02.0f}:{seconds:06.3f}'
    return record