Logging kit

Drop-in logging for Python and Flask projects. No colors. Rotating file + console. Optional JSON file output. Safe in or out of Flask context.

For projects where I want logs formatted like this:

2023-03-26 11:42:29,661 INFO in auth_routes.py:93 [login]: Attempting login for username 'superadmin1'
2023-03-26 11:42:29,981 INFO in auth_routes.py:98 [login]: Password correct for user ID '671'
2023-03-26 11:42:30,151 INFO in dashboard_routes.py:31 [dashboard]: Super Admin 1 (671) accessed the dashboard
2023-03-26 11:43:14,388 INFO in rbac.py:57 [perm_req]: Checking permissions for Super Admin 1 (671)
2023-03-26 11:43:14,388 INFO in rbac.py:66 [perm_req]: Permission 'user_view_all' is required
2023-03-26 11:43:14,475 INFO in rbac.py:87 [perm_req]: Access Granted. Super Admin 1 (671) has permission 'user_view_all'
2023-03-26 11:43:14,475 INFO in user_routes.py:24 [users]: Super Admin 1 (671) viewed the users list page

With this I simplify the process so I can add log statements like this:

log_info("Attempting login for username '%s'", username)
log_warning("Failed login attempt for %s", username)
log_error("Some error happened...")

Package layout

src/
  my_logging/
    __init__.py             # exports init_logging + log_* helpers
    config.py
    filters.py
    formatters.py
    init_logging.py
    helpers/__init__.py     # log_debug/log_info/log_warning/log_error/log_critical

Quick start (plain Python)

from my_logging import init_logging, log_info, log_warning, log_error, log_critical

init_logging()  # creates logs/app.log (5MB rotate, 20 backups)
log_info("service started")
log_warning("using defaults")
log_error("example problem")

Quick start (Flask)

from flask import Flask
from my_logging import init_logging, log_info

def create_app():
    app = Flask(__name__)
    init_logging(app=app)   # attaches handlers to app.logger, silences noisy libs
    @app.route("/")
    def ping():
        log_info("ping")
        return "ok"
    return app

Env vars (optional)

LOG_DIR=logs
LOG_FILE=app.log
LOG_LEVEL=INFO
LOG_CONSOLE_LEVEL=DEBUG
LOG_FILE_LEVEL=INFO
LOG_MAX_BYTES=5242880
LOG_BACKUP_COUNT=20
LOG_FORMAT_CONSOLE="%(asctime)s %(levelname)s in %(module)s [%(funcName)s]: %(message)s"
LOG_FORMAT_FILE="%(asctime)s %(levelname)s in %(filename)s:%(lineno)d [%(funcName)s]: %(message)s"
LOG_JSON_FILE=0   # 1 enables JSON lines for file handler

Notes

• Handlers are reset on init to avoid duplicates.
• log_* helpers prefer Flask.current_app.logger when available, else fall back to the root logger.
• ANSI codes are stripped in formatters to keep files clean.
• werkzeug, sqlalchemy.engine, socketio, and engineio are set to WARNING by default. Use silence_noisy_libs() to adjust.

License

MIT