Fly.io

The Fly.io Production Stack ships maintained modules that turn your Stackpanel apps into Fly Machines, complete with multi-region distribution, autoscale, health probes, secret sync, and observability dashboards.

If you want apps close to users in many places without running your own bare-metal fleet, this is the stack for you.

What's in the flake

• Per-app Fly modules that auto-generate apps/<app>/fly.toml, a per-app deploy task, and wrapped flyctl commands like fly-api status.
• Container builds via nix2container — minimal, reproducible OCI images with no Dockerfile required.
• Secrets sync that pushes SOPS-encrypted Stackpanel variables into Fly secrets on deploy.
• Multi-region machine layouts: declare regions, machine sizes, autoscale rules, and minimum machines per region.
• Health probes wired to your app's /healthz (or custom path).
• Observability: Fly's built-in metrics shipped to your dashboards; optional OpenTelemetry exporters.
• PR preview apps with auto-cleanup on PR close (Business tier and above).

Installation

Add the flake input:

{
  inputs = {
    stackpanel.url = "github:darkmatter/stackpanel";
    stack-fly.url = "github:darkmatter/stack-fly";
  };
}

Enable the stack:

{
  stackpanel.stacks.fly = {
    enable = true;
    branch = "stable";
    organization = "acme";
    defaultRegion = "iad";
  };
}

A minimal example

{
  stackpanel.apps.api = {
    path = "apps/server";
    framework.hono.enable = true;

    fly = {
      enable = true;
      appName = "acme-api";
      regions = [ "iad" "fra" "syd" ];
      machine = {
        cpus = 1;
        memory = "512mb";
      };
      autoscale = {
        minMachines = 1;
        maxMachines = 6;
        autoStop = "suspend";
        autoStart = true;
      };
      health = {
        path = "/healthz";
        intervalSeconds = 15;
      };
      env = [ "DATABASE_URL" "STRIPE_SECRET_KEY" ];
    };
  };
}

Deploy:

# Wrapped flyctl commands generated per deployable app
fly-api status
fly-api logs
fly-api deploy

# Or via the per-app deploy task
bun --cwd packages/infra run deploy:api

What we maintain

Fly ships features fast — autoscale rules, machine classes, regional features. Subscriptions get patches for:

• Fly Machines API: when Fly bumps their REST API or flyctl flags.
• fly.toml schema: tracking new fields (vm sizing, services, mounts, etc.).
• nix2container: rebuilding minimal OCI images as the base layers evolve.
• Health probe semantics: as Fly tightens the liveness / readiness contract.
• Secret rotation: automated re-sync on SOPS recipient changes.
• Observability exporters: Prometheus, OpenTelemetry collector configs.

Tier differences

Related

• Production Stacks overview
• Deployment / Fly.io — the underlying Fly module reference
• Deployment / Containers