[Distutils] Docker, development, buildout, virtualenv, local/global install

[Ionel Cristian Mărieș]

On Wed, Jun 15, 2016 at 12:07 PM, Reinout van Rees <reinout at vanrees.org>
wrote:

> Now local development: it is normal to mount the current directory as
> /code/, so that now is overlayed over the originally-added-to-the-docker
> /code/.
>
> This means that anything done inside /code/ is effectively discarded in
> development. So a "bin/buildout" run has to be done again, because the
> bin/, parts/, eggs/ etc directories are gone.
>
​
Think of it like this: if you don't mount ./ as /code in the container then
you practically have to rebuild the image​ all the time. This is fine for
toy projects, but bigger ones have lots of files (eg: templates, images,
css, tons of js 1-line modules etc). That means you get a big context that
is slow to send (exacerbated in situations that have remote docker daemons
like osx/windows docker clients).

​Another compound problem: if you rebuild the image for every code change
the new context will invalidate the docker image cache - everything will be
slow, all the time. Ideally you'd have a stack of images, like a base image
that takes big context (with code/assets) + smaller images that build from
that but have very small contexts. I wrote some ideas about that here
<https://blog.ionelmc.ro/2016/05/07/dealing-with-docker/#optimizing-the-build-process>
if you have patience (it's a bit too long read).

Basically what I'm saying is that you got no choice but to mount stuff in a
development scenario :-)

Regarding the buildout problem, I suspect a src-layout can solve the
problem:

   - you only mount ./src inside container
   - you can happily run buildout inside the container (assuming it don't
   touch any of the code in src)

I suspect you don't need to run buildout for every code change so it's fine
if you stick that into the image building.

Thanks,
-- Ionel Cristian Mărieș, http://blog.ionelmc.ro
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