Runners

A runner is a long-running process that hosts connect to. It authenticates each host, finds the plugin package the host names among its installed packages, and starts a plugin process for it. Hosts never send code.

Set up a runner

1. Install @graftland/cli, @graftland/plugin-remote, the built plugin packages and their dependencies in the node_modules of an installation directory, on Linux or macOS with Node.js 22.22 or later. Expose each contract and implementation through package exports, such as my-plugin/contract and my-plugin. The host needs the contract package; the runner needs both packages.
2. Write runner.yml with one remote/runner entry.
3. Start the runner with graft start runner.yml.
4. Point the host’s remote entry at it and run graft start host.yml.

runner.yml

- id: runner
  name: remote/runner
  config:
    root: ./installation
    state: ./state
    listen:
      - url: wss://0.0.0.0:7443
        cert: ./certs/server.crt
        key: ./certs/server.key
        auth:
          jwt:
            issuer: https://issuer.example
            audience: [graft]
            algorithms: [ES256]
            keys:
              jwksUrl: https://issuer.example/.well-known/jwks.json

host.yml

- id: greeter
  name: remote
  config:
    contract: my-plugin/contract
    implementation: my-plugin
    connect:
      url: wss://runner.example:7443
      ca: ./certs/ca.crt
      auth:
        jwt:
          token: { file: ./runner-token.txt }
    config:
      greeting: Hello

Field	Required	Default	Meaning
root	Yes	—	Installation directory. Contract and implementation packages resolve from its node_modules.
state	Yes	—	State directory, created if missing. See the rules below.
lease	No	15 seconds	Default lease for instances.
grace	No	5 seconds	Time between interrupting a plugin process and killing it.
listen	Yes	—	Listeners, one per address. See listen forms.

Rule	Detail
Paths	Relative to runner.yml, including root, state and certificate files.
Installation	Keep it unchanged while the runner runs. To deploy, install the new package, then restart the entry on the host.
State directory	On a local filesystem, used by one runner at a time, kept across restarts. A second runner fails with StateDirectoryLocked.
Fresh state	Do not start an empty state directory for identities still in use elsewhere: generations would start over.
Startup command	graft start runner.yml. Logs go to standard error. Use --stdio only with a single stdio listener.
Startup	Complete only when every listener is ready. A failure closes what was opened and exits nonzero with the startup cause.
A listener fails later	The runner logs Remote listener failed; other listeners and plugins keep running.
Service manager	Run the runner under one that stops all its descendants, such as systemd with KillMode=control-group.

listen forms

Form	Fields
url: ws://host:port	No cert or key.
url: wss://host:port	cert and key: the server certificate and key.
unix: path	The socket file to create.
stdio: true	identity, default anonymous. No auth. See SSH and stdio.
transport: { name, config }	A custom listener.

• Each element takes one transport form and at most one auth, from Transport and authentication.
• WebSocket listeners serve one path, /graft, with the subprotocol graft-remote.v1. A url path must be empty or /graft. There are no other HTTP endpoints and no health check.
• All listeners share one set of instances, and together use at most one JWT issuer.

Instances

An instance is the name of a plugin slot on the runner. With the host’s identity from authentication, it decides which plugin process a connection belongs to. A new connection for the same identity and instance replaces the old process, and its start gets the next generation. The state directory keeps generations per identity and instance.

Case	What to do
Default name	The loader entry’s id. Keep it stable; the loader saves generated ids in the config file.
Two hosts, same identity and instance	They replace each other. Give each host its own identity, or set a distinct connect.instance.
Two remote plugins forked from one entry	Children inherit the entry id. Set connect.instance on each.
Embedded groups	Group ids are unique only among siblings. Check the resulting names.
Remote.plugin without the loader	No entry id. Set connect.instance, or loading fails with MissingInstance.

connect.expect pins what the runner has installed before the plugin starts:

connect:
  url: wss://runner.example:7443
  expect:
    version: 1.4.0

Field	Compared with
version	The version in the implementation package’s package.json on the runner.
digest	A SHA-256 hex digest of the package’s files, excluding every node_modules, so not its dependencies. Computed only when set.

A mismatch fails with PackageError, whose message shows both values.

SSH and stdio

A stdio runner speaks over standard input and output, so a host can reach it with a command such as SSH. SSH then authenticates and encrypts.

/srv/graft/stdio.yml

- id: runner
  name: remote/runner
  config:
    root: /srv/graft/installation
    state: /srv/graft/state/billing
    listen:
      - stdio: true
        identity: billing

Restrict the host’s key to that command in the runner account’s authorized_keys, and connect with command:

restrict,command="/usr/local/bin/graft start /srv/graft/stdio.yml --stdio" ssh-ed25519 AAAA... billing-host

connect:
  command: [ssh, -T, [email protected]]

Rule	Detail
No auth	Neither command nor stdio takes auth, not even none. identity only names the host.
One listener	A stdio listener is its runner’s only listener.
One state directory	Give each SSH identity its own. A second session on the same directory at the same time is refused.
Session end	At end of input, graft start stops the plugin, confirms its exit, releases the state directory and exits 0; on failure it exits nonzero with the cause.
Clean output	Standard output carries protocol bytes. Use -T and print no banners.
Exit proof	SSH exiting does not prove the plugin stopped; only the runner’s confirmation does.