docker: use slim base images to reduce size

There's probably still a lot of improvements to make here, but this is a pretty big size reduction to begin with

Base Image	Built Image Size
python:3.8	1.11 GB
python:3.8-slim	410 MB

If we want to take things further, here's a breakdown of where the bytes come from:

IMAGE          CREATED          CREATED BY                                      SIZE      COMMENT
8c96c42b044d   8 minutes ago    CMD ["/bin/sh" "-c" "bash -c \"./scripts/sta…   0B        buildkit.dockerfile.v0
<missing>      8 minutes ago    COPY /app/dist /code/tau-dashboard/dist # bu…   4.75MB    buildkit.dockerfile.v0
<missing>      8 minutes ago    COPY . /code # buildkit                         1.86MB    buildkit.dockerfile.v0
<missing>      31 minutes ago   COPY supervisord.conf /etc/supervisord.conf …   744B      buildkit.dockerfile.v0
<missing>      31 minutes ago   RUN /bin/sh -c pip install -r requirements.t…   194MB     buildkit.dockerfile.v0
<missing>      32 minutes ago   COPY requirements.txt . # buildkit              1.14kB    buildkit.dockerfile.v0
<missing>      32 minutes ago   WORKDIR /code                                   0B        buildkit.dockerfile.v0
<missing>      32 minutes ago   RUN /bin/sh -c pip install supervisor git+ht…   2.76MB    buildkit.dockerfile.v0
<missing>      32 minutes ago   RUN /bin/sh -c apt update && apt install -y …   82.6MB    buildkit.dockerfile.v0
<missing>      32 minutes ago   ENV PYTHONUNBUFFERED=1 PYTHONHASHSEED=random…   0B        buildkit.dockerfile.v0
<missing>      2 days ago       /bin/sh -c #(nop)  CMD ["python3"]              0B
<missing>      2 days ago       /bin/sh -c set -eux;   savedAptMark="$(apt-m…   11.4MB
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PYTHON_GET_PIP_SHA256…   0B
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PYTHON_GET_PIP_URL=ht…   0B
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PYTHON_SETUPTOOLS_VER…   0B
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PYTHON_PIP_VERSION=22…   0B
<missing>      2 days ago       /bin/sh -c set -eux;  for src in idle3 pydoc…   32B
<missing>      2 days ago       /bin/sh -c set -eux;   savedAptMark="$(apt-m…   28.5MB
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PYTHON_VERSION=3.8.16    0B
<missing>      2 days ago       /bin/sh -c #(nop)  ENV GPG_KEY=E3FF2839C048B…   0B
<missing>      2 days ago       /bin/sh -c set -eux;  apt-get update;  apt-g…   3.11MB
<missing>      2 days ago       /bin/sh -c #(nop)  ENV LANG=C.UTF-8             0B
<missing>      2 days ago       /bin/sh -c #(nop)  ENV PATH=/usr/local/bin:/…   0B
<missing>      2 days ago       /bin/sh -c #(nop)  CMD ["bash"]                 0B
<missing>      2 days ago       /bin/sh -c #(nop) ADD file:493a5b0c8d2d63a13…   80.5MB

We can see from the logs that this line is adding 194MB to the image: https://github.com/Team-TAU/tau/blob/818fd8750a4913ee45b687b640145b8cefe1bc8d/Dockerfile#L22

I'm not too familiar with the dependencies of the project, so I'm not sure which ones might be adding this;

Also, the fact that we need to install git in order to install the supervisor adds an additional 82.6MB to the image.

The lower bound using python:3.8-slim is around 130MB - if we want to go any smaller, we'd need to switch to alpine.

Testing

I tested this by deploying the image to my existing TAU instance - everything still appears to be working, and I don't see any app errors in the logs.

Team-TAU / tau

docker: use slim base images to reduce size #129

Testing