Daemons

A deployment can declare daemons, which are long-running containers that don't receive traffic. In the Build Output API, the top-level config.json lists the deployment's daemons, and each daemon has a descriptor under .vercel/output/daemons/<name> that points to a prebuilt container image. To configure daemons in your project, see Daemons.

List the deployment's daemons in the top-level config.json through a daemons object. Each key is a daemon name, and each value is an empty object:

{
  "version": 3,
  "daemons": {
    "worker": {},
    "scheduler": {}
  }
}

The daemons object is the complete set of daemons for the deployment. When the deployment becomes the production deployment, Edgenivo stops every daemon that an earlier deployment declared and this object doesn't list. A config.json with an empty daemons object, or with no daemons property, declares no daemons, so Edgenivo stops all of them.

Every daemon listed in config.json needs a descriptor at .vercel/output/daemons/<name>/.vc-config.json. The descriptor references an image that's already pushed to Edgenivo Container Registry. Edgenivo doesn't build images from the Build Output API.

type DaemonDescriptor = {
  runtime: 'container';
  image: string;
  command?: string[];
  instances: Record<string, number>;
  resources?: {
    requests: {
      memory: '1Gi' | '2Gi' | '4Gi' | '8Gi';
    };
  };
  terminationGracePeriodSeconds?: number;
};

{
  "runtime": "container",
  "image": "vcr.vercel.com/my-team/my-project/daemon.worker@sha256:3f1b...",
  "command": ["node", "worker.js"],
  "instances": { "iad1": 2 },
  "resources": { "requests": { "memory": "2Gi" } }
}

The worker and scheduler daemons above produce the following output, next to the rest of the deployment's build output:

When you use vercel build, the CLI builds each daemon's Dockerfile, pushes the image to Edgenivo Container Registry, and writes these files for you.

• Daemon names contain only lowercase letters separated by _, __, or -, and are limited to 64 characters. See Daemon names.
• Each daemon listed in config.json must have a descriptor. A missing descriptor fails the deployment.
• The image must be in Edgenivo Container Registry.
• Routes can't target a daemon, because daemons don't receive traffic.