[Jarred]

CI has always been expensive for Bun including before the acquisition. We build for [macOS, Linux, FreeBSD, Android, Windows] x [ARM64, x64] and then run tests on multiple Linux distros with multiple shards, multiple macOS versions and Windows for each architecture.

We recently started cross-compiling all the builds on Linux arm64 and that made it a little faster (I wrote a CLI tool to download the correct macOS headers for cross-compilation). We also have a daily cron job that asks claude to make the slowest tests faster while adding more assertions.

[sandeepkd]

I think the question for CI costs is still out there. While I do not think it should be in tunes of thousands a day but thats the skepticism presented in the article. True costs are really important to make a good decision in situations like this. One has to consider the fact that lots of people are going to use these numbers to justify the rewrite in future.

[JustSkyfall]

How come Bun uses Buildkite instead of self-hosting the CI infra?

[Jarred]

It spawns ephemeral EC2/Azure instances, which is a lot cheaper than the GitHub actions runners we used before that.

We shard to a lot of machines for tests and I’d be worried about running out if we used dedicated servers.

BuildKite is fine but I wouldn’t be that surprised if we move off of BuildKite to a custom thing at some point. Months ago, we switched from CMake to a handrolled typescript build system and it made our builds faster and simpler.

[JustSkyfall]

Thanks for answering!

I suppose my second question would be how much Bun spends on CI per month atm - I'd imagine that robobun would have ramped up the bill a fair bit

[latchkey]

you don't need buildkite or blacksmith anymore.

codex trivially built me a self-hosted gh actions runner workflow for ephemeral vm's (just a big bash script that manages the vms with qemu). i even sped up the builds with my own custom base image with everything installed in it that i need too.

it works flawlessly.

fanning that out to starting and stopping instances wouldn't be too much of a stretch.

[m00dy]

Does it work with macOS ?

[latchkey]

weird question, i don't see why not. osx has a fantastic virtualization story.

https://developer.apple.com/documentation/virtualization/run...

[m00dy]

bro, I was a committer for libvirt

[simonw]

Presumably because they "build for [macOS, Linux, FreeBSD, Android, Windows] x [ARM64, x64]" and self hosting all of that would be time-consuming and expensive.

[CamouflagedKiwi]

Probably because they don't want to self-host Windows or MacOS servers when they can pay someone else to do that for them (or Linux ones, I assume that is within their wheelhouse for production but CI is a bit of a different beast to model inference).

[jojobas]

So are the "$800k + CI" estimates accurate? And your team works weekends just to make tests faster?