NEX-7: Configure logging framework

.gitignore

@@ -7,6 +7,7 @@ __pycache__
 
 # Pytest folders
 .pytest_cache
+logs
 reports
 
 # Node.js

app.py

@@ -1,30 +1,92 @@
+import os
+import logging
+
 from flask import Flask
+from logging.handlers import RotatingFileHandler
+from typing import Mapping
 
 
-def create_app():
+def create_app(config: Mapping):
     """
-    Creates and configures the Flask application instance. Intended for use by both production and test code.
+    Creates and configures the Flask application instance using the provided config mapping.
+
+    :param config: The config mapping containing configuration key-value pairs
     """
     app = Flask(__name__)
+
+    app.config.from_mapping(config)
+    configure_logging(app)
+    app.logger.info("Creating Flask application instance")
+
     # TODO: Secure this before deploying into production
     app.secret_key = "cUrR33_ChI_#"
 
     # Configure app
-    app.config.from_mapping(
-        {
-            "FLASK_ENV": "development",
-        }
-    )
+    app.logger.debug(f"Using application configuration {config}")
 
     # Register routes via Flask blueprint
     from routes import app_blueprint
 
+    app.logger.info("Registering server endpoints")
     app.register_blueprint(app_blueprint)
 
     return app
 
 
-app = create_app()
+def configure_logging(app: Flask):
+    """
+    Configure logging for the Flask application. Attempts to get the log level from a LOG_LEVEL environment variable,
+    defaults to INFO if environment variable not set.
+
+    :param app: The Flask app instance to configure logging on
+    """
+
+    # Get log level from env-var, default to INFO if env-var invalid or not set
+    log_level = logging.getLevelName(os.getenv("LOG_LEVEL"))
+
+    if log_level is None or isinstance(log_level, str):
+        log_level = logging.INFO
+
+    app.logger.setLevel(log_level)
+
+    # Clear default handler
+    #
+    # TODO: Configure logging before creating the Flask app instance to prevent default handler from being added.
+    # TODO: See https://flask.palletsprojects.com/en/stable/logging/
+    app.logger.handlers.clear()
+
+    # Create and configure formatter
+    detailed_formatter = logging.Formatter(
+        "[%(asctime)s.%(msecs)03d] %(levelname)s (%(module)s): %(message)s",
+        "%Y-%m-%d, %H:%M:%S"
+    )
+
+    # Create and configure console handler for development logging
+    console_handler = logging.StreamHandler()
+    console_handler.setLevel(logging.DEBUG)
+    console_handler.setFormatter(detailed_formatter)
+    app.logger.addHandler(console_handler)
+
+    # Add file handler with rotation for longer-running production deployments, omit during testing
+    if not bool(app.config["TESTING"]):
+        # Create logs directory if it doesn't exist
+        if not os.path.exists("logs"):
+            os.mkdir("logs")
+
+        # Max 10MB per file, keep 10 backup files
+        file_handler = RotatingFileHandler(
+            "logs/netex.log", maxBytes=10 * 1024 * 1024, backupCount=10  # 10MB
+        )
+        file_handler.setLevel(logging.INFO)
+        file_handler.setFormatter(detailed_formatter)
+        app.logger.addHandler(file_handler)
+
 
 if __name__ == "__main__":
+    # TODO: Support environment- and file-based configuration
+    app = create_app(
+        {
+            "FLASK_ENV": "development",
+        }
+    )
     app.run(debug=True)

routes.py

@@ -1,12 +1,19 @@
 import humanize
 import xarray
 
-from flask import Blueprint, redirect, render_template, request, session, url_for
+from flask import (
+    Blueprint,
+    current_app,
+    redirect,
+    render_template,
+    request,
+    session,
+    url_for,
+)
 from http import HTTPMethod
 from io import BytesIO
 
 
-
 app_blueprint = Blueprint("netex", __name__)
 
 FILE_SESSION_KEY = "netcdf_file"
@@ -17,6 +24,9 @@
 def index():
     if request.method == HTTPMethod.POST:
         netcdf_file = request.files["netcdf_file"]
+        current_app.logger.debug(
+            f"Received NetCDF summary request for file '{netcdf_file.filename}'"
+        )
         if netcdf_file:
             # Get file size
             netcdf_file.seek(0, 2)
@@ -34,13 +44,17 @@ def index():
                 url_for("netex.summary", netcdf_filename=netcdf_file.filename)
             )
 
+    current_app.logger.debug("Received GET request for index page")
     return render_template("index.html.jinja")
 
 
 @app_blueprint.get("/summary/<netcdf_filename>")
 def summary(netcdf_filename):
     summary = session["summary_text"]
     file_size = session["file_size"]
+
+    current_app.logger.debug(f"Showing summary for file '{netcdf_filename}'")
+
     return render_template(
         "summary.html.jinja",
         file_name=netcdf_filename,

tests/conftest.py

@@ -3,16 +3,17 @@
 import pytest
 
 from app import create_app
+from tests import constants
 
 # TODO: Explain why this is needed for tests
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 
 @pytest.fixture(scope="class")
 def test_client():
-    flask_app = create_app()
-
-    flask_app.config["TESTING"] = True
+    flask_app = create_app(
+        {"FLASK_ENV": "development", "TESTING": constants.SET_TESTING_CONFIG}
+    )
 
     # Create a test client using the Flask application configured for testing
     with flask_app.test_client() as test_client:

tests/constants.py

@@ -0,0 +1,2 @@
+# Adds the "TESTING" config to the Flask app if True
+SET_TESTING_CONFIG = True

tests/unit/app_test.py

@@ -1,5 +1,6 @@
 from app import create_app
 from http import HTTPMethod
+from tests import constants
 
 
 class TestApp:
@@ -12,11 +13,11 @@ def test_app_contains_index_route(self):
         WHEN create_app() is called
         THEN a Flask app with an index route ("/") supporting GET and POST methods should be returned.
         """
-        app = create_app()
+        app = create_app({"TESTING": constants.SET_TESTING_CONFIG})
 
         # Assert configs
         assert app is not None
-        assert app.config["FLASK_ENV"] == "development"
+        assert app.config["TESTING"] == constants.SET_TESTING_CONFIG
         assert app.secret_key is not None
 
         url_map = app.url_map
@@ -26,7 +27,7 @@ def test_app_contains_index_route(self):
         index_rule = routes[0]
 
         assert index_rule.rule == "/"
-        
+
         assert HTTPMethod.GET in index_rule.methods
         assert HTTPMethod.POST in index_rule.methods
 
@@ -35,7 +36,7 @@ def test_app_contains_summary_route(self):
         WHEN create_app() is called
         THEN a Flask app with a "/summary/{netcdf_filename} route supporting only the GET method should be returned.
         """
-        app = create_app()
+        app = create_app({"TESTING": True})
 
         url_map = app.url_map
         # Assert summary route is registered and supports GET method