Migrate from Travis CI to Gitlab CI

[emilypi]

I just know @fommil will be on board with this one.

Gitlab CI is now available for free for all open-source projects on github. Considering our near-constant Travis CI woes and our history of pushing the envelope at Scalaz, I am proposing we move to Gitlab to make our workflow more consistent, and faster.

What does Gitlab offer?

• Ease of use: Gitlab's CI is much simpler to understand. Travis is rather opaque, and diagnosing build problems is a pain. Gitlab has great documentation supporting its use.

• It has a more up to date and usable UI

• Tests run in parallel on as many machines as you procure. Additionally you can spin up multiple builds in parallel on the same machine.

• multiple stages, manual deploys, environments, and variables

• Open source: Gitlab's CI/CD is open source.

Why do we care?

There are many problems with Travis that do not necessarily stem from our builds failing. Builds fail randomly, hang, and are notoriously slow using the Travis approach. Rather than spinning up a single VM per build, it makes more sense to run CI in parallel on multiple, which solves the congestion problem in a more holistic way. Additionally, Travis is a pain to work with diagnostically. To me, Gitlab seems like the way forward in the future.

@jdegoes @xuwei-k @edmundnoble @TomasMikula @alexknvl @hrhino @fommil @tonymorris

[edmundnoble]

This could probably bring our sz8 build/test times to near zero if we manage caching correctly, which is much harder on Travis and (IME) costly.

Edit: With that said, I don't know much about the differences between CI systems in practice.

[fommil]

I agree that Travis is Problematic.

[emilypi]

@fommil objectively Problematic

[tonymorris]

I don't know enough to give a useful comment. I know that Travis is problematic enough that it should disappear. If there is a useful option otherwise, do it.

[NeQuissimus]

It's not supposed to be free forever, if I understand correctly:

For GitLab.com users, GitLab CI/CD for GitHub will be available promotionally in our Free tier through March 22, 2019. (After March 22, 2019 it will move to the Silver tier and be available on Silver and Gold.)

[emilypi]

@NeQuissimus that's not what was described in the section for Open Source Projects

If you have a public, open source project on GitHub you can now take advantage of free CI/CD on GitLab.com. As part of our commitment to open source, we offer all public projects our highest tier features (Gold) for free. While other CI/CD vendors limit you to running a handful of concurrent jobs, GitLab.com gives open source projects hundreds of concurrent jobs with 50,000 free CI pipeline minutes.

I hope OSS is not subject to the changes in availability. That would be something to confirm. The wording of this gives me hope tho.

[NeQuissimus]

Oh, OK, so OSS gets Gold for free. CI/CD goes from the Free Tier into Silver/Gold in March. Should be OK then as long as we sign up as a Gold OSS account?!

[emilypi]

That's what I hope to confirm with them. The language seems to indicate that, but it's best to be sure 😄