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CI Infrastructure for Holochain

This is the declarative deployment of the holochain CI infrastructure. All hosts are running either Linux or MacOS.

The linux hosts are managed via NixOS and the MacOS hosts are managed via nix-darwin.

For making changes to the nixos configuration files, please refer to the nixos manual.

For making changes to the macos configuration files, please refer to the nix-darwin manual.

Development on this repo

This repository uses nix flakes. To interact with it, add the experimental features flakes and nix-command to your ~/.config/nix/nix.conf:

experimental-features = flakes nix-command

Flakes have a standardized output schema, for which a good overview exists in the nixos wiki.

Before getting started, it is always a good idea to inspect the outputs of the current project:

nix flake show

Notice the field nixosConfigurations which lists all hosts managed by this repo.

Repo structure

To change the definition of some attribute seen in nix flake show, adapt the files under ./modules/flake-parts. The file and directory names seen in the flake-parts directory are similar to the flake output names.

Example: The definition for nixosConfigurations.linux-builder-01 is located at ./modules/flake-parts/nixosConfigurations.linux-builder-01.

Code shared between hosts should be factored out into one or more nixos modules located under ./modules/nixos/.

Module types & File structure

This project splits up its nix code into modules in order to improve maintainability and portability of the code.

There are two kinds of modules:

There are two kinds of modules:

  • nixos modules: located under ./modules/nixos
    • contain configuration for linux or macos hosts.
  • flake-parts modules: located under ./modules/flake-parts
    • export entities like packages, apps, or machine configurations via the flake outputs, the projects public API so to speak.
    • are responsible for everything seen in the output of nix flake show.

A new flake module can be added by creating a new file under ./modules/flake-parts. (Or a new directory containing a default.nix file)

A template for initializing new modules is located under ./modules/flake-parts/_template.nix.

For more information on how to write flake modules, visit flake.parts.

Deploying changes

After making changes to the configuration files of a host, a flake app must be executed in order to apply the changes to that host.

Show available apps

nix flake show

notice apps prefixed with ssh-, git-push-, and deploy-.

Deploy changes to host

Prerequisites:

  • all relevant changes are committed to the current branch.
  • git push access to holochain/holochain-infra
  • authorized key for the deployUser on the remote host

The first command will push the current git HEAD to the origin git remote at a branch specific to the hostname. The second command will cause a nixos-rebuild switch ... on the host from its branch.

nix run .\#git-push-{hostname}
nix run .#deploy-{hostname}

These scripts also have arguments for rudimentary customization. Here, it pushes to the git remote called upstream, and then runs a build (instead of a switch) on the remote host:

nix run .\#git-push-sbd-0_main_infra_holo_host upstream
nix run .\#deploy-sbd-0_main_infra_holo_host build

Update dependencies (nixpkgs version)

nix flake update

Common Error Cases

Github Action Runners are down

If a runner appears offline in the runners settings page we can inspect and potentially restart the service.

In the root of this repo:

nix run .\#ssh-linux-builder-01

# on the remote host, we can inspect the status of a runner that appears problematic on GitHub, e.g.
systemctl status github-runner-multi-arch-0.service

Before debugging too much, restarting one, or all as shown below, is worth attempting:

systemctl restart github-runner-multi-arch-*.service

Upgrading the GitHub runner version

If a runner appears offline in the runners settings page and when SSHing into the host with nix run .\#ssh-linux-builder-01 and checking journalctl -b0 --unit "github*" -n 200 shows that the runner can't start because the runner software is deprecated then try the following steps.

(optional) Update the flake.nix by pointing nixpkgs and home-manager.url at the latest stable release branch. These two must match since home-manager also references nixpkgs.

Update the flake.lock based on your changes

nix flake lock --update-input nixpkgsGithubActionRunners

If that works, check that everything builds successfully on the builder

nix run .#deploy-linux-builder-01 build

If that also works then ask nixos to apply these changes without updating the default profile

nix run .#deploy-linux-builder-01 test

If the runners are back online then update the default profile

nix run .#deploy-linux-builder-01 switch

TURN stack

  • [Adding a new machine]

  • Double-check that all TURN/Signal servers are ready:

     nix run .#turn-readiness-check

Bind refuses to start after an update

The error message

journal rollforward failed: journal out of sync with zone

This can be fixed by removing the journal files.

Upon connection via SSH (nix run .\#ssh-dweb-reverse-tls-proxy ):

systemctl stop bind
rm /etc/bind/zones/infra.holochain.org.zone.jnl
systemctl start bind