How to deploy NiceGUI application to Heroku?

[200729]

I tried to deploy hellord app on Heroku:
code:

from nicegui import ui
import os

ui.label('Hello NiceGUI!')
ui.button('BUTTON', on_click=lambda: print('button was pressed', flush=True))

port = int(os.getenv('PORT'))
ui.run(port=port)

and I have error:

Exception: Could not find ui.run() command

Is possible to deploy on Heroku?

[falkoschindler]

Thanks for your feedback! You spotted an issue in NiceGUI's pre-evaluation of the ui.run command. Already during import we try to find this command at the end of the main script in order to tell whether the server should start with auto-reload or not. This works well in most cases. But when the specified port (or any other argument) is a variable or an even more complex expression, our pre-evaluation fails.

But we can avoid terminating the whole app and simply continue evaluating the script in a so-called interactive mode (same as if NiceGUI is used in an interactive Python shell). The auto-reloading feature does not work here, but at least the UI starts as expected and whatever expression is passed to ui.run will be evaluated correctly.

Please have a try with version 0.7.13. I haven't tested it on Heroku, yet. But I'm pretty confident that this new release will solve your issue.

[200729]

Thanks for quick answer and fix! I tried version 0.7.13 and error Exception: Could not find ui.run() command is not visible. However as it is in life of a programmer fixing one error discovers another error :D Now there is a warning, but application crashes. Warning seems to be from justpy:
WARNING: You must pass the application as an import string to enable 'reload' or 'workers'.
Do you have idea how to fix it?

[falkoschindler]

Oh, that's interesting. Would you mind sharing your deployment setup like Procfile, requirements.txt and runtime.txt? I could imagine that Heroku has trouble finding the right entry point for the guvicorn server.

[200729]

Sure, here is whole hello world project in zip nicegui_tets.zip

[falkoschindler]

Thanks! I identified two issues, one regarding your Heroku Settings and one deep inside the NiceGUI configuration... I'm still working on it. 🤞

[falkoschindler]

With version 0.7.15 it finally seems to work as expected. See my other answer for more details.

[falkoschindler]

The new NiceGUI version 0.7.15 should finally work nicely on Heroku. The main issue was that the environment variable PORT has been overwritten by the import statement from nicegui import ui. But now the variables HOST and PORT - if defined - will be read and used during ui.run(). So you don't even need to read them via os.getenv and pass them to ui.run.

In the meantime I thought using Heroku's default setting of WEB_CONCURRENCY=2 might be an issue. So I experimented with setting it to 1. But with version 0.7.15 this step is probably not necessary anymore.

So my final setup is as follows:

main.py

from nicegui import ui

label = ui.label('Hello NiceGUI!')
ui.button('BUTTON', on_click=lambda: label.set_text(label.text + '!'))

ui.run()

Procfile

web: python main.py

requirements.txt

nicegui==0.7.15

runtime.txt

python-3.9.10

[200729]

Great! Thank you! It is working now.

[alikalik9]

Hi, I am trying to deploy to Heroku using the same set up and I am getting the following error message:
Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch

[falkoschindler]

Hi @alikalik9! I'm not sure about this Error R10. We are currently working on another problem with Heroku (#469).
@rodja Do you think this could be related? Either way, I guess we need some documentation about hosting with Heroku.

[alikalik9]

Thanks for the quick answer. Yes, a documentation for Heroku (or any other convinient provider) would be much appteciated!
Keep up the good work!