Hetzner

Host your cluster on Hetzner Cloud: Postgres runs on a Server with a Volume, and each runner runs on a Server of its own, all on a private Network. A Load Balancer serves the pool’s gateway, so a Hetzner Service or anything else calls the rooms by id.

src/Cluster.ts

import * as ClusterHetzner from "@alchemy.run/effect-cluster/Hetzner";
import * as Layer from "effect/Layer";

export const Database = ClusterHetzner.Database("Cluster");

export const Default = ClusterHetzner.ServerPool("Default", { replicas: 2 }).pipe(
  Layer.provide(Database),
);

Install @alchemy.run/hetzner and finish Hetzner setup.

Hetzner projectyour profile's project

Load Balancerchecks /health

Networkprivate

DatabaseServer · Postgres

data

Volume

DefaultServerPool

Serverrunner

Serverrunner

Runners reach Postgres and each other over the Network, and their firewalls let only SSH in from outside. The Load Balancer finds the Servers by label.

The database

ClusterHetzner.Database creates a private Network and runs Postgres in Docker on a Server with a Volume. Its firewall drops every connection to its public address; runners reach it over the Network.

src/Cluster.ts

import * as ClusterHetzner from "@alchemy.run/effect-cluster/Hetzner";

export const Database = ClusterHetzner.Database("Cluster", {
  location: "fsn1",
  serverType: "cx33",
  diskSize: 50,
});

The pool

ClusterHetzner.ServerPool creates one Server per runner on the Network, and runs the pool’s program on each as a Hetzner.Service. Runners reach each other over the Network; their firewall only lets SSH in, which deploys them. The Load Balancer finds the Servers by label and checks each at /health.

Call it from a Hetzner Service

src/Api.ts

import * as Hetzner from "@alchemy.run/hetzner";
import * as Effect from "effect/Effect";
import * as HttpServerResponse from "effect/http/HttpServerResponse";
import { Room } from "./Room.ts";

export const ApiServer = Hetzner.Server("ApiServer", {
  serverType: "cx23",
  image: "ubuntu-24.04",
  location: "nbg1",
});

export default class Api extends Hetzner.Service<Api>()(
  "Api",
  { server: ApiServer, main: import.meta.url },
  Effect.gen(function* () {
    const rooms = yield* Room;
    return {
      fetch: Effect.gen(function* () {
        const lobby = yield* rooms.getByName("lobby");
        return yield* HttpServerResponse.json({ members: yield* lobby.Join({ name: "sam" }) });
      }).pipe(Effect.orDie),
    };
  }),
) {}

Every option, with its default, is in the reference: Database and ServerPool.