Cross-Platform GitHub Action

I would like to announce the first version of a project I've been working on for a while. It's not anything D specific or implemented in D, but it can be used with D projects. This project provides a GitHub action for running GitHub Action workflows on multiple platforms. This includes platforms that GitHub Actions don't natively support. It currently supports FreeBSD and OpenBSD.

https://github.com/cross-platform-actions/action

Features

Some of the features that are supported include:

• Multiple operating system with one single action
• Multiple versions of each operating system
• Allows to use default shell or Bash shell
• Low boot overhead
• Fast execution

Compared to vmactions/freebsd-vm, the boot time is around a fifth and the full execution time for the same job is around half of freebsd-vm.

Usage

Here's a sample workflow file which will setup a matrix resulting in two jobs.
One which will run on FreeBSD 12.2 and one which runs on OpenBSD 6.8.

name: CI

on: [push]

jobs:
  test:
    runs-on: macos-10.15
    strategy:
      matrix:
        os:
          - name: freebsd
            version: 12.2
          - name: openbsd
            version: 6.8

    steps:
      - uses: actions/checkout@v2

      - name: Test on ${{ matrix.os.name }}
        uses: cross-platform-actions/action@v0.0.1
        env:
          MY_ENV1: MY_VALUE1
          MY_ENV2: MY_VALUE2
        with:
          environment_variables: MY_ENV1 MY_ENV2
          operating_system: ${{ matrix.os.name }}
          version: ${{ matrix.os.version }}
          shell: bash
          run: |
            uname -a
            echo $SHELL
            pwd
            ls -lah
            whoami
            env | sort

I've been using this action for one of my own projects (DLP) for now close to a week and it works fine. It's mostly FreeBSD that has been tested.

If you're interested in how the sausage is made, read on. Also see the readmes of the builder repositories:

https://github.com/cross-platform-actions/freebsd-builder
https://github.com/cross-platform-actions/openbsd-builder

Under the Hood

GitHub Actions currently only support the following platforms: macOS, Linux and
Windows. To be able to run other platforms, this GitHub action runs the commands
inside a virtual machine (VM). macOS is used as the host platform because it
supports nested virtualization.

The VMs run on the xhyve hypervisor, which is built on top of Apple's
Hypervisor framework. The Hypervisor framework allows
to implement hypervisors with support for hardware acceleration without the
need for kernel extensions. xhyve is a lightweight hypervisor that boots the
guest operating systems quickly and requires no dependencies outside of what's
provided by the system.

The VM images running inside the hypervisor are built using Packer.
It's a tool for automatically creating VM images, installing the guest
operating system and doing any final provisioning.

The GitHub action uses SSH to communicate and execute commands inside the VM.
It uses rsync to share files between the guest VM and the host. xhyve
does not have any native support for sharing files. To authenticate the SSH
connection a unique key pair is used. This pair is generated each time the
action is run. The public key is added to the VM image and the private key is
stored on the host. Since xhyve does not support file sharing, a secondar hard
drive, which is backed by a file, is created. The public key is stored on this
hard drive, which is then mounted by the VM. At boot time, the secondary hard
drive will be identified and the public key will be copied to the appropriate
location.

To reduce the time it takes for the GitHub action to start executing the
commands specified by the user, it aims to boot the guest operating systems as
fast as possible. This is achieved in a couple of ways:

• By downloading resources, like xhyve and a few other tools,
  instead of installing them through a package manager

• No compression is used for the resources that are downloaded. The size is
  small enough anyway and it's faster to download the uncompressed data than
  it is to download compressed data and then uncompress it.

• It leverages async/await to perform tasks asynchronously. Like
  downloading the VM image and other resources at the same time

• It performs as much as possible of the setup ahead of time when the VM image
  is provisioned

Thx for sharing! Interesting; I've recently worked on something similar, but on Linux hosts and using a kvm/qemu/libvirt stack for running CI jobs in Windows VMs.

On Tuesday, 8 June 2021 at 19:40:01 UTC, kinke wrote:

Yeah, this is running on macOS instead because the Linux and the Windows runners on GitHub actions don't support nested virtualization. The Hypervisor framework is something similar to KVM. The VM images are actually created using QEMU (on Linux hosts), because Packer doesn't have any support for Xhyve. Packer will create a qcow2 VM image. At run time, the qcow2 image will be converted to the "raw" format, which is the only format that Xhyve supports. qcow2 is used up until runtime because it natively supports compression.

I do want to support other operating systems going forward, but unfortunately, it's only FreeBSD and OpenBSD that work in Xhyve. For other operating systems I will have to use QEMU. QEMU does support the Hypervisor framework as an accelerator, but I don't think it will be as fast as Xhyve.

When QEMU is supported, it will hopefully be trivial to add support for non-native architectures. I've already built the OpenBSD image for ARM64.

--
/Jacob Carlborg

On Wednesday, 9 June 2021 at 05:20:14 UTC, Jacob Carlborg wrote:

Just a note from terms of service:
you get 2000 minutes available for Github Actions every month for free, however for using Windows hosts it takes 2x minutes and Mac hosts takes 5x minutes.

On Tuesday, 8 June 2021 at 19:10:41 UTC, Jacob Carlborg wrote:

Neat.

~Brian

On Tuesday, 8 June 2021 at 20:39:45 UTC, Steven Schveighoffer wrote:

I don't think that would work. The VM is only running during one step. When the step is done, the VM is terminated. Also, Docker doesn't support FreeBSD or OpenBSD. I don't plan to add platforms which GitHub Actions natively support.

On the other hand, it seems pretty straightforward to install MySQL natively on macOS:

brew install mysql
brew services start mysql

There are also several GitHub Actions that will setup MySQL:

https://github.com/marketplace?type=actions&query=mysql

--
/Jacob Carlborg