Refactor grpc-balancer to use Gunicorn and update playbook.yml for deployment

- Replaced the SSL server implementation in grpc-balancer.py with Gunicorn for improved performance and scalability.
- Updated playbook.yml to use Gunicorn for starting the grpc-balancer service, including SSL certificate configuration.
- Removed the waitress dependency in favor of Gunicorn, streamlining the application setup.

grpc-balancer.py

@@ -318,11 +318,4 @@ if __name__ == '__main__':
     upload_thread = threading.Thread(target=upload_stats_to_grist, daemon=True, args=(grist_callback,))
     upload_thread.start()
 
-    from waitress import serve
-    import ssl
-    
-    ssl_context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
-    ssl_context.load_cert_chain('/root/node/cert.pem', '/root/node/key.pem')
-    
-    logging.info(f"Starting SSL server on port {PORT}")
-    serve(app, host='0.0.0.0', port=PORT, threads=MAX_WORKERS, connection_limit=1000, _ssl_context=ssl_context)
+    app.run(host='0.0.0.0', port=PORT)

playbook.yml

@@ -200,7 +200,7 @@
           - grist-api
           - flask
           - requests
-          - waitress
+          - gunicorn
         extra_args: --break-system-packages
 
     - name: Create SSL certificate for grpcbalancer
@@ -229,7 +229,7 @@
           Type=simple
           User=root
           WorkingDirectory={{ ansible_env.HOME }}/node
-          ExecStart=/usr/bin/python3 {{ ansible_env.HOME }}/node/grpc-balancer.py
+          ExecStart=/usr/local/bin/gunicorn --certfile=/root/node/cert.pem --keyfile=/root/node/key.pem -b 0.0.0.0:5000 grpc-balancer:app
           Restart=always
           RestartSec=2