Add Dockerfile variant for clustered deployment on Fly.io

[jonatanklosko]

Preview

There is still an issue related to booting apps that I need to address.

[github-actions]

Uffizzi Preview deployment-38881 was deleted.

[josevalim]

Shall we move the static variables out of the script?

[jonatanklosko]

Is there a specific reason? If we could move them all that would make sense, but since LIVEBOOK_NODE is runtime, I would keep together for consistency.

[josevalim]

The idea was to keep only runtime ones in the runtime script. Also, any thoughts in an approach like this?

ENV ERL_AFLAGS "-proto_dist inet6_tcp"
ENV LIVEBOOK_DISTRIBUTION name
CMD [ 'sh', '-c' , 'LIVEBOOK_NODE="${FLY_APP_NAME}-${FLY_IMAGE_REF##*-}@${FLY_PRIVATE_IP}" LIVEBOOK_CLUSTER="dns:${FLY_APP_NAME}.internal" /app/bin/livebook start']

[jonatanklosko]

The idea was to keep only runtime ones in the runtime script.

Yeah, the practical difference is whether the env vars are set globally, which I don't think they necessarily should be? Also, normally all of these would go to env.sh.eex, that's why I prefer to keep them together.

I considered CMD, which we could even break it into multiple lines, but what I like about creating a startup file is that usually you'd have that file alongside and COPY it, so it's the closest to that (and if the user wants to do that, it's easy). Also for CMD you actually must use double quotes, because because technically it is parsed as a JSON array 🙈

# Custom startup script to cluster multiple Livebook nodes on Fly.io
RUN printf '\
#!/bin/bash\n\
export ERL_AFLAGS="-proto_dist inet6_tcp"\n\
export LIVEBOOK_DISTRIBUTION="name"\n\
export LIVEBOOK_NODE="${FLY_APP_NAME}-${FLY_IMAGE_REF##*-}@${FLY_PRIVATE_IP}"\n\
export LIVEBOOK_CLUSTER="dns:${FLY_APP_NAME}.internal"\n\
/app/bin/livebook start\n\
' > /app/bin/start.sh && chmod +x /app/bin/start.sh

CMD [ "/app/bin/start.sh" ]

vs

# Custom startup script to cluster multiple Livebook nodes on Fly.io
CMD [ "sh", "-c" , "\
  ERL_AFLAGS=\"-proto_dist inet6_tcp\" \
  LIVEBOOK_DISTRIBUTION=\"name\" \
  LIVEBOOK_NODE=\"${FLY_APP_NAME}-${FLY_IMAGE_REF##*-}@${FLY_PRIVATE_IP}\" \
  LIVEBOOK_CLUSTER=\"dns:${FLY_APP_NAME}.internal\" \
  /app/bin/livebook start" ]