, 14 tweets, 7 min read Read on Twitter
.@gsaslis and @mikz say that any project needs CI, but OSS projects need it more!
#DevopsDays Slide: any project needs CI, but OSS ones need it more!
I think @DRMacIver and @alexwlchan would probably agree with this. #hypothesis #isThereAnOfficialHypothesisHashtagYet
CI is supposed to run in the background, whenever you push changes—but if you’re stuck waiting for the tests to run, it’s not in the background, is it? @gsaslis #DevopsDays
With >30 mins cold build times, the 3Scale team in Barcelona would go out to lunch together, come back from lunch together, and rush to push their builds to beat the others to the CI. 😂#DevOpsDays
Their homegrown EC2 + Jenkins parallel CI was slow and inconvenient, so what did @mikz and @gsaslis choose instead? Here’s their shopping list.

(Yes, people have mined cryptocurrency on paid CI before...!) Publicly accessible, prioritise builds from their team, builds from forks are not paid by RedHat (abuse)
Answer: they picked @circleci, because the tests are accessible without any login; they didn’t have to maintain the CI servers (yay); you can bucket tests by timing (ooh, nice); and rerun tests only from the point where they failed. #DevopsDays
Ooh, and you can ssh into containers, nice.
🎉They halved what they were paying for CI because of better resource usage, while increasing team size. Lesson learned: it’s better to use a fleet of short-lived containers than VMs. #DevopsDays
Cons: CircleCI is less configurable than Jenkins, an external dependency, and not fully OSS (though they’ve opened up some of their stuff). #DevopsDays
We see their cool new workflow. How did they get to this point? “We just had to run the tests a thousand times, it was easy!”

@mikz now tells us how they fixed flaky tests. Some relied on state, or didn’t clean up their state properly, or depended on other tests. #DevopsDays
(The answer is to run the tests a lot, in random order, and measure how things fail. Phew. 😅) #DevopsDays
Question: it takes four CPU hours to build and run your test suite, and you ran it 100s or 1000s of times: what’s the environmental impact? 🌍

Answer: we got it down from 11 CPU hours, and we run it much less now everything is optimised, only when pushing. (Cont.) #DevOpsDays
(Cont.) Really this talk is about reducing waste, of dev time, resources and money. We loved our tests and now they love us back. #DevopsDays

(Great question and answer, imo.)
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