using docker multi staging

[iham]

is there any approach towards using multi staging as docker supports?

as far as i understand the concept, it would be possilbe to split the created images into

• 1st stage: a basic python (with zc.buildout and setuptools installed based on requirements.txt)
• 2nd stage: a basic plone buildout (basic system packages and all the default eggs)
• 3rd stage: a custom plone buildout (extended system packages and additional eggs)
• 4th stage: the running instance (system build deps removed)

and for zeo purpose separate stages using the basic python stage:

• 2nd stage: a basic zeo buildout (basic system packages and all the default eggs only needed for zeo)
• 3rd stage: the running zeo (system build deps removed)

i see some advantages here:

• faster docker builds, as previous unchanged stages will not compile over and over again
• each stage can handle its own entrypoints and commands
  • while the basic plone buildout hat entrypoint "buildout" and CMD could be "-vvv" or such, the running instance has ENTRYPOINT "./bin/instance" and CMD "start"
• the docker-initialize.py and entrypoint.sh would be gone
  • switching inside the docker what might happen could be achieved more explicit
  • customising the docker image you want to build might become more handy
• in docker-compose you can select a stage you want to use "target"

as i don't see disadvantages i am ... in doubt ;)

any comments on that?
anybody already tried but failed horribly?
any concerns?

please share your thoughts.

thanks

[avoinea]

@iham

As I have almost no experience with multi staging builds, don't fully rely on my opinion, but I tend to like your proposal.

I also think that this will work best when we will use pip to install Plone #89

I think we also had an earlier discussion about moving to build stages within #90, but nothing materialized.

Thus, I would love to see a pull-request on this and/or some working examples.

[iham]

thanks for pointing out @avoinea