I'm very new to pantsbuild and pex files. I'm trying to run a very simple fast-api application from a pex file using a container/pex packaged using pants. I'm able to run the application using the pex file with

./pants run src/python/maergo:main

. When attempting to run the application via docker with

./pants run src/docker/maergo:python

I encounter the following:

Failed to find compatible interpreter on path /usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin.

Examined the following interpreters:
1.) /usr/local/bin/python3.10 CPython==3.10.7
2.)        /usr/bin/python3.9 CPython==3.9.2

No interpreter compatible with the requested constraints was found:

  Failed to resolve requirements from PEX environment @ /root/.pex/unzipped_pexes/dbe958d0761ce1dbfdab65e69c2ae9a4658f75b5.
  Needed cp310-cp310-manylinux_2_31_aarch64 compatible dependencies for:
   1: pydantic!=1.7,!=1.7.1,!=1.7.2,!=1.7.3,!=1.8,!=1.8.1,<2.0.0,>=1.6.2
      Required by:
        fastapi 0.85.2
      But this pex had no ProjectName(raw='pydantic', normalized='pydantic') distributions.
   2: pydantic<2.0.0,>=1.10.2
      But this pex had no ProjectName(raw='pydantic', normalized='pydantic') distributions.

This is a link to my test repository. Is there some other dependency I need to add to my Dockerfile to enable the execution of pex files?

So

cp310-manylinux_2_31_aarch64

- appears to be your Python / arch, what is the arch of the

python:3.10-bullseye

image?

support running Pants build steps in containers though.

-> this would be amazing

Yeah, I'm not fully versed in where that stands but @happy-kitchen-89482 probably knows better.

I think so

The other possibility is its glibc < 2.31

So I need to add a value for platform to the pex_binary ?

Yes.

I guess it's not clear to me what platform value I need. I'm getting the follow error when trying to package with a platform value:

ResolveError: The file or directory 'linux-x86_64-pp-310-none' does not exist on disk in the workspace, so the address 'linux-x86_64-pp-310-none' from the `complete_platforms` from the target src/python/maergo:main cannot be resolved.

We are building Linux images on macOS too. We do it via complete platforms: we have

3rdparty/platforms/

which contains a

BUILD

like the following, along with

docker_python_3_9_10_bullseye_amd64.json

and

docker_python_3_9_10_bullseye_arm64.json

(amd vs. arm) generated by the commands listed

# docker run -it --platform linux/arm64 python:3.9.10-bullseye bash -c 'pip install pex; pex3 interpreter inspect --markers --tags'
# docker run -it --platform linux/amd64 python:3.9.10-bullseye bash -c 'pip install pex; pex3 interpreter inspect --markers --tags'
files(
    name="docker_python_3_9_10_bullseye",
    sources=["docker_python_3_9_10_bullseye_*.json"],
)

(you'll presumably need to change the image used) This is then referred to like

pex_binary(...,  complete_platforms=("3rdparty/platforms:docker_python_3_9_10_bullseye",))

Slightly annoyingly, we build an ARM image on macOS, and an x86-64/AMD image on CI, hence having both complete platforms.

@broad-processor-92400 Thanks for chiming in! The disconnect for me is how do I define a complete platform? Could you share your

docker_python_3_9_10_bullseye_amd64.json

file? Also at what point to execute the

docker run

commands specified above?

Huon gave you the command lines right there above!

So are those images (docker runs) built outside of pants? The other thing that isn't clear to me is what should be in docker_python_3_9_10_bullseye_amd64.json? Sorry I think something is clicking for me this morning

Yes, this is a 1 time step outside of Pants to create a complete platform json file you then configure Pants with. You use a container that contains the exact Python you're targeting.

Thanks again for the help @enough-analyst-54434 and @broad-processor-92400!