Docker compose builds pip 6 times

[cdolfi]

In the docker compose pip is built 6 times, is this necessary?
https://github.com/chaoss/augur/blob/main/docker/backend/Dockerfile#L105-119

[MoralCode]

i doubt it is necessary - if it was i suspect there would be a comment explaining why its necessary

you could at least get it down by ~ half by removing either the RUN call that does them all in one step, or the three that splits it out separately

I personally would probably also try and remove the venv things and just install directly, because at that point youre running an isolated virtual environment (designed to help keep things separated on a host that has multiple programs with possibly conflicting dependencies) into a container (which is seemingly used as a single-purpose environment just for augur)

while not directly related, i figure id also add #3006 as a reference since i probably would have mentioned this if i had noticed it while filing that issue/PR

[cdolfi]

That makes senes. In the docker clean up process cutting this down a bit might be a good idea