Temporary fix scale docker compose

[machow]

@mdbecker this should allow deploying multiple streamlit containers (I couldn't tell via streamlit docs and code, whether their tornado implementation uses subprocesses. Guessing not, based on their emphasis on load balancers).

Once merged, I'll go ahead and deploy on the linode box (and then hopefully the devops team will swoop in and save us 😅)

I don't set up load balancers that often so any eyes on this would be helpful!

[themightychris]

@machow I've never used this scaling ability of docker-compose, but I'm struggling to see how this could actually make multiple app instances available to nginx. If the port is constant, than either docker-compose would need to be round-robining the IP set on app somehow, or nginx would need to have some kind of capability to make its own DNS query and get back multiple IPs on a single A record -- but I doubt either of those setups are in place here (I could be wrong though)

I don't know that it's worth us diving too deep into docker-compose-based scaling strategies though if this isn't something we already know will work, k8s deploy should be ready soon and we know it will handle managing multiple app instances

[themightychris]

Hmm nvm sounds like docker-compose does round-robin the DNS and people talk about that working behind nginx, I'd expect nginx to be caching DNS on things it's proxy_passing to... ¯_(ツ)_/¯

[machow]

I'm surprised docker even implemented a feature like this, but it turned out weirdly useful in this case.