Development composer dependencies and php extensions (xdebug)

[Voziv]

Hello!

First off I want to thank you for the awesome work you've been doing with these "good-defaults" repos. They've been immensely insightful.

I have a few questions about creating a production image.

1. Would it make sense to have development dependencies omitted for the production build? Currelty I added --prefer-dist and --no-dev to composer to exclude the dev libraries and download .zip files instead of cloning repos.

2. What would be sane to install the xdebug extension only in development?

I'll try to update this issue as I find out more information. Any insight you may be able to provide as well is greatly appreciated!

[BretFisher]

Yes, ideally prod doesn't have any dev-only dependencies. There are several major ways to do this, of which none are yet implemented in this repo (but I would love PR's)

• Build an intermediate image for production that is CI-tested and stored in a registry, then build a dev-only image on top of that for local dev.
• Use multi-stage builds to build a single image, but make an earlier stage the one you use in compose file (you can specify a stage name in compose image: command)

There are lots of pros and cons to each of these as well as likely other options. Many are hidden in the nuance of how your team develops, tests, and deploys software so it's hard to capture it all in a few bullet points, but in general:

• Automation in CI and building image and deploying updates to the registry are key with PHP
• Because build times can be quite long, and you'll often want to figure out how to prevent developers from having long build times locally
• What you don't want is two separate non-dependent images for dev and prod, which will create "configuration drift" and remove one of the main benefits of containers, which is to remove the "works on my machine" scenario.

[Voziv]

As I work on these containers for my work I'll look into making PRs with my discoveries!

[vctls]

I'm currently using multi-stage builds in a Symfony project. I got my inspiration from Sylius-Standard. I know these guys are serious about best practices. What I did was a first parent php stage, followed by two separate test and dev php stages (I'm not using Docker in prod, yet).

from php:7.2 as php-base
# build the base image. Put all common parts here.
# …

from php-base as php-test
# COPY sources and stuff
# …

from php-base as php-dev
# install xdebug
# bind mount sources, etc.

There's one hiccup with those multi-stage builds, though: apparently, there's no way of telling Docker NOT to build a stage if you don't need it in a specific environment.

[BretFisher]

@vctls The "skip building a stage if not needed" was not a feature of the original docker build. That's now built into BuildKit and the new docker buildx in the upcoming 19.03 release.