Refactored to use Flask app factory pattern

Author: rofrano

.devcontainer/docker-compose.yml

@@ -11,7 +11,7 @@ services:
       - ..:/app
     command: sleep infinity
     environment:
-      FLASK_APP: service:app
+      FLASK_APP: wsgi:app
       FLASK_DEBUG: "True"
       CLOUDANT_HOST: couchdb
       CLOUDANT_PORT: 5984

.github/workflows/build.yml

@@ -38,19 +38,22 @@ jobs:
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip wheel
-          pip install -r requirements.txt
+          python -m pip install -U pip poetry
+          poetry config virtualenvs.create false
+          poetry install
 
       - name: Create the test database
         run: |
           apt-get update
           apt-get install -y curl
           curl -X PUT http://admin:pass@couchdb:5984/test
 
-      - name: Run unit tests with green
-        run: green
+      - name: Run unit tests with pytest
+        run: pytest --pspec --cov=service --cov-fail-under=95 --disable-warnings
         env:
+          FLASK_APP: "wsgi:app"
           BINDING_CLOUDANT: '{"username":"admin","password":"pass","host":"couchdb","port":5984,"url":"http://admin:pass@couchdb:5984"}'
 
       - name: Upload code coverage
         uses: codecov/codecov-action@v3.1.4
+

Dockerfile

@@ -0,0 +1,31 @@
+##################################################
+# Create production image
+##################################################
+FROM python:3.11-slim
+
+# Establish a working folder
+WORKDIR /app
+
+# Establish dependencies
+COPY pyproject.toml poetry.lock ./
+RUN python -m pip install poetry && \
+    poetry config virtualenvs.create false && \
+    poetry install --without dev
+
+# Copy source files last because they change the most
+COPY wsgi.py .
+COPY service ./service
+
+# Switch to a non-root user and set file ownership
+RUN useradd --uid 1001 flask && \
+    chown -R flask:flask /app
+USER flask
+
+# Expose any ports the app is expecting in the environment
+ENV FLASK_APP=wsgi:app
+ENV PORT 8080
+EXPOSE $PORT
+
+ENV GUNICORN_BIND 0.0.0.0:$PORT
+ENTRYPOINT ["gunicorn"]
+CMD ["--log-level=info", "wsgi:app"]

Procfile

@@ -1 +1 @@
-web: gunicorn --bind 0.0.0.0:$PORT --log-level=info service:app
+web: gunicorn --bind 0.0.0.0:$PORT --log-level=info wsgi:app

service/__init__.py

@@ -30,60 +30,73 @@
 # The Flask app must be created
 # BEFORE you import modules that depend on it !!!
 
-# Create the Flask app
-app = Flask(__name__)
-app.config.from_object(config)
-
-# Turn off strict slashes because it violates best practices
-app.url_map.strict_slashes = False
-
 # Document the type of authorization required
 authorizations = {
     "apikey": {
-        "type": "apiKey", 
-        "in": "header", 
+        "type": "apiKey",
+        "in": "header",
         "name": "X-Api-Key"
     }
 }
 
-######################################################################
-# Configure Swagger before initializing it
-######################################################################
-api = Api(
-    app,
-    version="1.0.0",
-    title="Pet Demo REST API Service",
-    description="This is a sample server Pet store server.",
-    default="pets",
-    default_label="Pet shop operations",
-    doc="/apidocs",  # default also could use doc='/apidocs/'
-    authorizations=authorizations,
-    prefix="/api",
-)
-
-
-# Import the routes After the Flask app is created
-# pylint: disable=wrong-import-position, wrong-import-order, cyclic-import
-from service import routes, models  # noqa: F401, E402
-from service.common import error_handlers
-
-# Set up logging for production
-log_handlers.init_logging(app, "gunicorn.error")
-
-app.logger.info(70 * "*")
-app.logger.info("  P E T   S E R V I C E   R U N N I N G  ".center(70, "*"))
-app.logger.info(70 * "*")
-
-app.logger.info("Service initialized!")
-
-# If an API Key was not provided, autogenerate one
-if not app.config["API_KEY"]:
-    app.config["API_KEY"] = routes.generate_apikey()
-    app.logger.info("Missing API Key! Autogenerated: %s", app.config["API_KEY"])
-
-try:
-    models.Pet.init_db(app.config["CLOUDANT_DBNAME"])
-except Exception as error:  # pylint: disable=broad-except
-    app.logger.critical("%s: Cannot continue", error)
-    # gunicorn requires exit code 4 to stop spawning workers when they die
-    sys.exit(4)
+# Will be initialize when app is created
+api = None  # pylint: disable=invalid-name
+
+
+############################################################
+# Initialize the Flask instance
+############################################################
+def create_app():
+    """Initialize the core application."""
+
+    # Create the Flask app
+    app = Flask(__name__)
+    app.config.from_object(config)
+
+    # Turn off strict slashes because it violates best practices
+    app.url_map.strict_slashes = False
+
+    ######################################################################
+    # Configure Swagger before initializing it
+    ######################################################################
+    global api
+    api = Api(
+        app,
+        version="1.0.0",
+        title="Pet Demo REST API Service",
+        description="This is a sample server Pet store server.",
+        default="pets",
+        default_label="Pet shop operations",
+        doc="/apidocs",  # default also could use doc='/apidocs/'
+        authorizations=authorizations,
+        prefix="/api",
+    )
+
+    with app.app_context():
+        # Import the routes After the Flask app is created
+        # pylint: disable=import-outside-toplevel
+        from service import routes, models  # noqa: F401, E402
+        from service.common import error_handlers   # pylint: disable=unused-import
+
+        try:
+            models.Pet.init_db(app.config["CLOUDANT_DBNAME"])
+        except Exception as error:  # pylint: disable=broad-except
+            app.logger.critical("%s: Cannot continue", error)
+            # gunicorn requires exit code 4 to stop spawning workers when they die
+            sys.exit(4)
+
+        # Set up logging for production
+        log_handlers.init_logging(app, "gunicorn.error")
+
+        app.logger.info(70 * "*")
+        app.logger.info("  P E T   S E R V I C E   R U N N I N G  ".center(70, "*"))
+        app.logger.info(70 * "*")
+
+        # If an API Key was not provided, autogenerate one
+        if not app.config["API_KEY"]:
+            app.config["API_KEY"] = routes.generate_apikey()
+            app.logger.info("Missing API Key! Autogenerated: %s", app.config["API_KEY"])
+
+        app.logger.info("Service initialized!")
+
+        return app

service/common/error_handlers.py

@@ -20,7 +20,8 @@
 Handles all of the HTTP Error Codes returning JSON messages
 """
 
-from service import app, api
+from flask import current_app as app  # Import Flask application
+from service import api
 from service.models import DataValidationError, DatabaseConnectionError
 from . import status
 

service/models.py

@@ -52,9 +52,9 @@
 CLOUDANT_PASSWORD = os.getenv("CLOUDANT_PASSWORD", "pass")
 
 # global variables for retry (must be int)
-RETRY_COUNT = int(os.getenv("RETRY_COUNT", 10))
-RETRY_DELAY = int(os.getenv("RETRY_DELAY", 1))
-RETRY_BACKOFF = int(os.getenv("RETRY_BACKOFF", 2))
+RETRY_COUNT = int(os.getenv("RETRY_COUNT", "10"))
+RETRY_DELAY = int(os.getenv("RETRY_DELAY", "1"))
+RETRY_BACKOFF = int(os.getenv("RETRY_BACKOFF", "2"))
 
 
 class DatabaseConnectionError(Exception):

service/routes.py

@@ -31,10 +31,11 @@
 import secrets
 from functools import wraps
 from flask import request
+from flask import current_app as app  # Import Flask application
 from flask_restx import Resource, fields, reqparse, inputs
 from service.models import Pet, Gender
 from service.common import status  # HTTP Status Codes
-from . import app, api
+from . import api
 
 
 ######################################################################

tests/test_routes.py

@@ -25,11 +25,12 @@
 
 import logging
 from unittest import TestCase
-from unittest.mock import patch
+# from unittest.mock import patch
 from urllib.parse import quote_plus
-from service import app, routes
+from wsgi import app
+from service import routes
 from service.common import status
-from service.models import DatabaseConnectionError
+# from service.models import DatabaseConnectionError
 from tests.factories import PetFactory
 
 # Disable all but critical errors during normal test run

wsgi.py

@@ -0,0 +1,13 @@
+"""
+Web Server Gateway Interface (WSGI) entry point
+"""
+
+import os
+from service import create_app
+
+PORT = int(os.getenv("PORT", "8000"))
+
+app = create_app()
+
+if __name__ == "__main__":
+    app.run(host="0.0.0.0", port=PORT)