How to deploy to Posit Connect

[zilch42]

Question

Hi there,

I'm trying to test whether NiceGUI will work on Posit Connect (I can't find any mention of the two together) before I get into learning it proper. Posit Connect works with FastAPI so I think it should work, but I'm currently stuck.

I'm just trying to upload the basic demo:

# app.py
from nicegui import ui

ui.label('Hello NiceGUI!')

ui.run()

I'm deploying it with:
rsconnect deploy fastapi -n rconnect --entrypoint app .

The deployment works but I get the following error on the Posit Connect logs when the app tries to start

2023/10/11 22:55:43.243207611 ERROR:    Traceback (most recent call last):
2023/10/11 22:55:43.243245111   File "/opt/rstudio-connect/mnt/app/python/env/lib/python3.9/site-packages/starlette/routing.py", line 677, in lifespan
2023/10/11 22:55:43.243275296     async with self.lifespan_context(app) as maybe_state:
2023/10/11 22:55:43.243276348   File "/opt/rstudio-connect/mnt/app/python/env/lib/python3.9/site-packages/starlette/routing.py", line 566, in __aenter__
2023/10/11 22:55:43.243296243     await self._router.startup()
2023/10/11 22:55:43.243306350   File "/opt/rstudio-connect/mnt/app/python/env/lib/python3.9/site-packages/starlette/routing.py", line 656, in startup
2023/10/11 22:55:43.243311926     handler()
2023/10/11 22:55:43.243312770   File "/opt/rstudio-connect/mnt/app/python/env/lib/python3.9/site-packages/nicegui/nicegui.py", line 75, in handle_startup
2023/10/11 22:55:43.243317822     raise RuntimeError('\n\n'
2023/10/11 22:55:43.243318250 RuntimeError: 
2023/10/11 22:55:43.243322835 
2023/10/11 22:55:43.243323595 You must call ui.run() to start the server.
2023/10/11 22:55:43.243330081 If ui.run() is behind a main guard
2023/10/11 22:55:43.243330511    if __name__ == "__main__":
2023/10/11 22:55:43.243334291 remove the guard or replace it with
2023/10/11 22:55:43.243334726    if __name__ in {"__main__", "__mp_main__"}:
2023/10/11 22:55:43.243338471 to allow for multiprocessing.
2023/10/11 22:55:43.243338936 

I've also tried

# app.py
from nicegui import ui

ui.label('Hello NiceGUI!')

app = ui.run()

and deploying it with:
rsconnect deploy fastapi -n rconnect --entrypoint app:app .

https://docs.posit.co/connect/user/fastapi/

Any help would be greatly appreciated

[rodja]

Hmm... does Posit Connect also allow arbitrary Python code to be deployed. There is much going on in ui.run() which would not be covered if you just specify the entrypoint "app". If that is not possible you can have a look at our FastAPI example: https://github.com/zauberzeug/nicegui/blob/main/examples/fastapi/main.py.

[zilch42]

Thanks @rodja for the quick response. The FastAPI example actually worked on Posit Connect (I was a little surprised. I wasn't sure if it would know to run uvicorn main:app --reload but it seemed to know what to do with it. I did still have to navigate to /show manually to get to the UI but that's probably workable.

I'm not really familiar with FastAPI either. I was wondering if you could please give me a brief description of what's going on in the example? Do I have a FastAPI running with a GUI sitting on top of it? Does that FastAPI matter or can I just happily ignore it's there and build out my app in frontend.py? What would someone normally use a FastAPI with a NiceGUI on top of it for?

Thanks

[rodja]

Yes, NiceGUI is just a FastAPI app. The FastAPI example demonstrates how to extend an existing FastAPI App to provide UI through the /show route. A simplified version which serves also the / as NiceGUI page would look like this:

from fastapi import FastAPI
from nicegui import app, ui

fastapi_app = FastAPI()

@ui.page('/')
def show():
    ui.label('Hello, FastAPI!')
    # NOTE dark mode will be persistent for each user across tabs and server restarts
    ui.dark_mode().bind_value(app.storage.user, 'dark_mode')
    ui.checkbox('dark mode').bind_value(app.storage.user, 'dark_mode')

ui.run_with(fastapi_app, storage_secret='secret')

if __name__ == '__main__':
    print('Please start with "uvicorn demo:fastapi_app --reload" (if your file is named "demo.py")')

[zilch42]

Thank you so much