The Latent Space

Recent Notes

Debugging with uvicorn

2 min read

Yes, it is possible to run Uvicorn in debug mode within VS Code to debug your FastAPI application. This involves configuring the VS Code debugger to run Uvicorn with your FastAPI application and enabling breakpoints for debugging.

Steps to Debug Uvicorn in VS Code

1. Install Required Extensions

Ensure you have the following extensions installed in VS Code:

  • Python (by Microsoft).
  • Debugger for Python.

2. Configure launch.json

Set up a debug configuration in VS Code.

  1. Go to the Run and Debug view in VS Code (Ctrl + Shift + D or click the play icon on the left sidebar).
  2. Click on “create a launch.json file” if you don’t already have one.
  3. Select “Python” as the environment.
  4. Add a configuration for Uvicorn:
{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug Uvicorn App",
      "type": "python",
      "request": "launch",
      "module": "uvicorn",
      "args": [
        "multiquery.app:app",
        "--reload",
        "--host",
        "127.0.0.1",
        "--port",
        "8000"
      ],
      "jinja": true
    }
  ]
}

3. Key Points in the Configuration

  • "module": "uvicorn":
    • This runs Uvicorn directly as a module (python -m uvicorn).
  • "args":
    • "multiquery.app:app": Path to your FastAPI app instance (app in multiquery/app.py).
    • "--reload": Enables hot-reloading for development.
    • "--host" and "--port": Specify the host and port for the app.
  • "jinja": true:
    • Useful if you’re using Jinja templates.

4. Set Breakpoints

  1. Open the files you want to debug (e.g., query.py, llm_service.py).
  2. Click in the gutter next to a line of code to set a breakpoint.

5. Start Debugging

  1. In the Run and Debug view, select the Debug Uvicorn App configuration.
  2. Click the green Start Debugging button (F5).
  3. VS Code will start the server, and you can use the debugger.

6. Test the Debugger

  1. Make a request to the server, such as:

    curl -X POST "http://127.0.0.1:8000/query/" \
     -H "Content-Type: application/json" \
     -d '{"prompt": "What is the capital of France?"}'

  2. Execution will pause at any breakpoints you’ve set, allowing you to inspect variables, step through code, and debug effectively.

Additional Tips

  • Inspect Variables: Use the debug console (Ctrl + ~) to inspect variables and test expressions.
  • Reload on Changes: If hot-reloading is causing issues, remove the --reload flag from the args section.
  • Performance Considerations: Debug mode is slower because of additional overhead, so use it for development only.

Let me know if you encounter any issues setting this up or need further clarification! 😊

debugging uvicorn python research development

Graph View

Backlinks