Add support for testing on Python 3.10

[H-Shay]

As the title states. One of the tasks outlined here: matrix-org/synapse#11780. Builds a new Docker image with debian:bookworm as the base, pushes it to DockerHub and adds the new image to CI for testing.

[DMRobertson]

https://packages.debian.org/bookworm/python3 seems to suggest that bookworm includes Python 3.9 by default. We'd have to explicitly opt-in to using 3.10 I think, by apt-installing this.

Does that sound right @richvdh ?

[richvdh]

Yup, looks that way. Not only that, we need to use it explicitly:

rav@fred:~$ docker run --rm -it debian:bookworm
root@294ab397ee09:/# apt update -qq
1 package can be upgraded. Run 'apt list --upgradable' to see it.
root@294ab397ee09:/# apt install -y python3
...
root@294ab397ee09:/# python3 --version
Python 3.9.10

root@294ab397ee09:/# apt install -y python3.10
...
root@294ab397ee09:/# python3 --version
Python 3.9.10
root@294ab397ee09:/# python3.10 --version
Python 3.10.2

... so I think we need to change synapse.Dockerfile to use python3.10 explicitly, as well as installing the right package.

Not sure if this is best done via docker build args (https://docs.docker.com/engine/reference/commandline/build/#set-build-time-variables---build-arg) or with a completely separate dockerfile.

[H-Shay]

I took a stab at using a separate dockerfile for building the 3.10 image and using it explicitly. I am none too familiar with docker but I think I succeeded, very open to feedback if I am wrong or there's a more elegant way to do this!

fixed, needs a re-review

[H-Shay]

So I have managed to ditch the custom dockerfile for python 3.10 and achieve the same result using a build arg passed to the generic synapse dockerfile. However, I was unable to figure out how to add this particular build to the strategy matrix: in particular, I could not figure out how to pass an extra build arg for python 3.10 in that one case. I am sure there is something very simple I am missing, but I banged my head against the wall long enough that's time to ask.

Edit: ignore me, I am an idiot and figured out the matrix out soon after I wrote this. I think this should be good to go now.

[richvdh]

looks good, a few more tweaks!

[richvdh]

the old sytest_image_tag variables seem to be unused now. Could you get rid of them?

[H-Shay]

I believe they are still being used on line 54?:

  name: "Build sytest-${{ matrix.dockerfile }}:${{ matrix.sytest_image_tag }}"

[richvdh]

oh yeah. Hrm, that's not ideal - they are bound to get out of sync.

Not sure I've got any better ideas right now though. Let's ship it!

[richvdh]

oh yeah. Hrm, that's not ideal - they are bound to get out of sync.

Not sure I've got any better ideas right now though. Let's ship it!