[Docs] Optimising for slow Docker builds

[benschwarz]

The "Optimising for slow docker Docker builds" found on the readme for this repo is really useful, but rather hidden on the elastic stack readme. (If someone uses docker, but not the elastic stack, they'd have a hard time finding this information).

I think it'd be super useful to move that content to a docs page of its own at Buildkite.com.

Additionally, I was wondering if you'd be able to clarify some of the points:

Update the pipeline’s env hook in your secrets bucket to perform a docker login

pipeline's env hook could maybe be a reference to something else in docs? I read it three times and I'm still not 100% sure what I'm looking for.

"secrets bucket" could also maybe be a link to higher up in the readme: "Build secrets". (and rename it to read 'build secrets bucket').

[lox]

@harrietgrace thoughts on where we should move this? I'm thinking perhaps in https://buildkite.com/docs/tutorials/elastic-ci-stack-aws? Alternately we could put it in https://buildkite.com/docs/tutorials/docker-containerized-builds.

[harrietgrace]

@lox I think in the Docker Containerized Builds docs for now - the Elastic Stack doc is too high level and getting-started-y for this section to fit in there.

It would be great to revise that Elastic stack doc sometime too... it could be so much more awesome than it currently is!

[plaindocs]

This is in the docs site now, and I've added a quick link to the environment hook.

Thanks!

[benschwarz]

Thanks for the update @plaindocs. I find this point particularly difficult to parse:

Update the pipeline’s environment hook in your secrets bucket to perform a docker login

I know what you're suggesting in practice, but there's 3 instructions in one sentence and it may be difficult for Buildkite newcomers. Maybe a more detailed example would be helpful?

[plaindocs]

Thanks @benschwarz , I'll take another look and break it down. :+1: