Hey pants, I'm creating a monrepo for multiple fastapi servers. I've figured most things out, but right now I'm stuck at creating a development server. I intend to use the pex binaries for deployment using docker, but during development we can't constantly rebuild the containers. I use uvicorn for serving, there are 2 ways to start a uvicorn server, from the shell

uvicorn module:app --reload

and programmatically

uvicorn.run(app)

Unfortunately uvicorn discontinued usage of reload while programmatically running the server, so for reload feature to work(crucial in a development environment), the command has to be executed via shell. I can't for the life of me figure out how to run a shell command or create a shell entrypoint with pants. Also it would be great if you guys could provide point me to an actual real world project with pants for a reference to make sure I'm doing this correctly.

@witty-crayon-22786 will

--loop

work in this case?

it won’t currently, but it could be made to: https://github.com/pantsbuild/pants/issues/9462#issuecomment-716821870

Hi @full-keyboard-92367! So the issue here is that Pants runs each process in a "sandbox", to ensure consistency and avoid unpredictable side-effects. But what that means is that if you run uvicorn via Pants (say via a

pex_binary

target) it will run from the sandboxed copy of your code, not the original in your source tree. So it won't "see" edits in your source tree.

One solution is to run uvicorn outside of Pants (in a virtualenv that Pants can build for you)

Ya I tried that, I followed https://www.pantsbuild.org/docs/python-third-party-dependencies#tip-set-up-a-virtual-environment-optional to create a venv, but I require pant's dependency injection to import a "common" module into my servers.

Is this common module in your source tree?

3rdparty src project_1 project_2 common this is my directory structure

I see, and are

project_1

,

project_2

and

common

different source roots (https://www.pantsbuild.org/docs/source-roots) ?

Yes

So you can try adding them all to PYTHONPATH

Hmm, so there's no way to use loop for this? (until https://github.com/pantsbuild/pants/issues/9462 is closed)

Not really... You could use

--loop

with

package

and relaunch when a new file is produced maybe?

don't apologize 😅 thanks for the project btw! 😎 👍

… thanks for the reminder. i’ll bump https://github.com/pantsbuild/pants/issues/9462 up my list.