How to Host a Flask Application on Vertra Cloud

my-api-flask/
├── app.py
├── requirements.txt
└── vertracloud.config

flask==3.0.0
gunicorn==21.2.0
psycopg2-binary==2.9.9
requests==2.31.0

MAIN=app.py
START=gunicorn --bind 0.0.0.0:$PORT app:app
VERSION=recommended

from flask import Flask, jsonify, request
import os
import psycopg2
from psycopg2.extras import RealDictCursor

app = Flask(__name__)

# Database connection
def get_db_connection():
    conn = psycopg2.connect(
        host=os.environ.get('DB_HOST'),
        database=os.environ.get('DB_NAME'),
        user=os.environ.get('DB_USER'),
        password=os.environ.get('DB_PASSWORD'),
        port=os.environ.get('DB_PORT'),  # unique per database, copy it from the dashboard
        # Vertra databases require TLS and the client certificate (see /databases)
        sslmode='verify-full',
        sslrootcert=os.environ.get('DB_SSL_PEM', 'certificate.pem'),
        sslcert=os.environ.get('DB_SSL_CRT', 'certificate.crt'),
        sslkey=os.environ.get('DB_SSL_KEY', 'certificate.key'),
    )
    return conn

@app.route('/')
def index():
    return jsonify({
        'message': 'Flask API on Vertra Cloud',
        'version': '1.0.0'
    })

@app.route('/health')
def health():
    return jsonify({
        'status': 'healthy',
        'client_ip': request.remote_addr
    })

@app.route('/api/items', methods=['GET'])
def get_items():
    try:
        conn = get_db_connection()
        cur = conn.cursor(cursor_factory=RealDictCursor)
        cur.execute('SELECT * FROM items LIMIT 10;')
        items = cur.fetchall()
        cur.close()
        conn.close()
        return jsonify(items), 200
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.route('/api/items', methods=['POST'])
def create_item():
    try:
        data = request.get_json()
        conn = get_db_connection()
        cur = conn.cursor()
        cur.execute(
            'INSERT INTO items (name, description) VALUES (%s, %s) RETURNING id;',
            (data['name'], data.get('description', ''))
        )
        item_id = cur.fetchone()[0]
        conn.commit()
        cur.close()
        conn.close()
        return jsonify({'id': item_id, 'name': data['name']}), 201
    except Exception as e:
        return jsonify({'error': str(e)}), 500

@app.errorhandler(404)
def not_found(error):
    return jsonify({'error': 'Not found'}), 404

@app.errorhandler(500)
def server_error(error):
    return jsonify({'error': 'Internal server error'}), 500

if __name__ == '__main__':
    port = int(os.environ.get('PORT', 5000))
    app.run(host='0.0.0.0', port=port)