fix: show app logs when running on gunicorn and change format

Set a nice log formatting to all logs, and make them work the same
whether the app is running with gunicorn or the default flask server.

This was not an easy task ^^'. Among the pitfalls:

- the app loggers need to be cleared since the app is created before
  the custom logging config is applied (to avoid duplicates)
- PYTHONUNBUFFERED need to be set in the Docker container since we
  are streaming logs in stdout
- setting the config directly in python doesn't work well when running
  with gunicorn: the first worker uses the new config, but the workers
  spawned afterwards will use the default config. We thus need
  to use the gunicorn.conf.py !

Dockerfile

@@ -38,6 +38,8 @@ FROM python:3.11-alpine3.17 as final
 # number of gunicorn workers to use
 ARG WORKERS=1
 ENV WORKERS=${WORKERS}
+# the logging config outputs to stdout, so we need unbuffered !
+ENV PYTHONUNBUFFERED=TRUE
 
 EXPOSE 8080
 WORKDIR /app
@@ -54,6 +56,7 @@ ENV PATH="/app/.venv/bin:$PATH"
 COPY --chown=app --from=venv /app/.venv .venv
 
 # gunicorn will automatically find modules in $PWD, and all deps are in venv
+COPY gunicorn.conf.py gunicorn.conf.py
 COPY rickroll rickroll
 
 # do not use curl, as it would have to be installed only for healthcheck...

gunicorn.conf.py

@@ -0,0 +1,8 @@
+from rickroll.log import logging_config
+from os import getenv
+
+# Apply custom log configuration when using gunicorn
+# Note that if this is done from the app itself, it won't be
+# applied to all workers...
+
+logconfig_dict = logging_config(getenv("APP_LOGGING_LEVEL", "INFO").upper())

rickroll/__init__.py

@@ -7,6 +7,10 @@
 from .rickroller import RickRoller
 
 app = Flask(__name__, static_folder="assets")
+# If we do not clear the default handlers, we will have duplicate logs
+# This is because we are in __init__.py, so neither main nor gunicorn
+# have run yet (they will set the logging config later)
+app.logger.handlers.clear()
 
 
 @app.errorhandler(Exception)

rickroll/__main__.py

@@ -1,17 +1,16 @@
 import argparse
-
 from rickroll import app
+from rickroll.log import logging_config
+from logging.config import dictConfig
 
+if __name__ == "__main__":
+    # apply logging config manually when not running with gunicorn
+    dictConfig(logging_config("DEBUG"))
 
-def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("--port", default="8080")
     parser.add_argument("--host", default="127.0.0.1")
     parser.add_argument("-d", "--debug", action="store_true")
     args = parser.parse_args()
 
     app.run(host=args.host, port=args.port, debug=args.debug)
-
-
-if __name__ == "__main__":
-    main()

rickroll/log.py

@@ -0,0 +1,51 @@
+# This logging configuration should be applied in gunicorn (see gunicorn.conf.py)
+# and when running flask directly (see __main__.py).
+# NOTES:
+#  - this requires PYTHONUNBUFFERED=True as we stream to stdout
+#  - since the app is created in __init__.py (which runs before anything else),
+#    the default handlers need to be cleared to avoid duplicate logs (app.logger.handlers.clear())
+
+
+def logging_config(app_log_level):
+    return {
+        "version": 1,
+        "disable_existing_loggers": True,
+        "formatters": {
+            "default": {"format": "%(asctime)s %(levelname)8s | %(message)s"},
+            "app": {
+                "format": "%(asctime)s %(levelname)8s > %(message)s  (%(filename)s:%(lineno)s)"
+            },
+        },
+        "handlers": {
+            "console": {
+                "level": "INFO",
+                "class": "logging.StreamHandler",
+                "formatter": "default",
+                "stream": "ext://sys.stdout",
+            },
+            "console_app": {
+                "level": "INFO",
+                "class": "logging.StreamHandler",
+                "formatter": "app",
+                "stream": "ext://sys.stdout",
+            },
+        },
+        "loggers": {
+            "gunicorn.error": {
+                "handlers": ["console"],
+                "level": "INFO",
+                "propagate": False,
+            },
+            "gunicorn.access": {
+                "handlers": ["console"],
+                "level": "INFO",
+                "propagate": False,
+            },
+            "rickroll": {
+                "handlers": ["console_app"],
+                "level": app_log_level,
+                "propagate": False,
+            },
+        },
+        "root": {"level": "INFO", "handlers": ["console"]},
+    }