github actions, remote builder vs local builder

[bulk88]

So my current fly app deploys using GH github Actions and follows the instructions here

Continuous Deployment with Fly.io and GitHub Actions

But I notice flyctl deploy --remote-only, so I assume 99% of the CPU to make the docker image, is running on a Fly VM, and not a GH VM. Can someone explain pros or cons, of why 2 VMs are running? How come the standard recipe doesn’t use the GH VM for heavy lifting? Is the fly VM faster than a GH Vm or base builder root fs image is somehow magically better start up/lower cpu/low ram/etc?

Could I cut out github actions and flyctl binary, and just run a REST/fetch() command from Cloudflare Workers or Chrome Browser or curl to run the Fly image builder VM?

[kurt]

Caching Docker layers in GitHub Actions is kind of complicated. The remote builder handles caching for you, so it’s generally faster unless you do a bunch of GitHub Actions config.

You can’t really get at the builders via HTTP. Our CLI connects to them over WireGuard.