Cluster - node__cluster.d.ts - Node

interface Cluster

extends EventEmitter

Usage in Deno

```typescript import { type Cluster } from "node:node__cluster.d.ts"; ```

> [!WARNING] Deno compatibility > This symbol is a non-functional stub.

Properties

deprecated

readonly



isMaster: boolean

readonly



isPrimary: boolean

True if the process is a primary. This is determined by the `process.env.NODE_UNIQUE_ID`. If `process.env.NODE_UNIQUE_ID` is undefined, then `isPrimary` is `true`.

readonly



isWorker: boolean

True if the process is not a primary (it is the negation of `cluster.isPrimary`).



schedulingPolicy: number

The scheduling policy, either `cluster.SCHED_RR` for round-robin or `cluster.SCHED_NONE` to leave it to the operating system. This is a global setting and effectively frozen once either the first worker is spawned, or [`.setupPrimary()`](https://nodejs.org/docs/latest-v22.x/api/cluster.html#clustersetupprimarysettings) is called, whichever comes first. `SCHED_RR` is the default on all operating systems except Windows. Windows will change to `SCHED_RR` once libuv is able to effectively distribute IOCP handles without incurring a large performance hit. `cluster.schedulingPolicy` can also be set through the `NODE_CLUSTER_SCHED_POLICY` environment variable. Valid values are `'rr'` and `'none'`.

readonly



settings: ClusterSettings

After calling [`.setupPrimary()`](https://nodejs.org/docs/latest-v22.x/api/cluster.html#clustersetupprimarysettings) (or [`.fork()`](https://nodejs.org/docs/latest-v22.x/api/cluster.html#clusterforkenv)) this settings object will contain the settings, including the default values. This object is not intended to be changed or set manually.

readonly

optional



worker: Worker | undefined

A reference to the current worker object. Not available in the primary process. ```js import cluster from 'node:cluster'; if (cluster.isPrimary) { console.log('I am primary'); cluster.fork(); cluster.fork(); } else if (cluster.isWorker) { console.log(`I am worker #${cluster.worker.id}`); } ```

readonly

optional



workers: Dict<Worker> | undefined

A hash that stores the active worker objects, keyed by `id` field. This makes it easy to loop through all the workers. It is only available in the primary process. A worker is removed from `cluster.workers` after the worker has disconnected _and_ exited. The order between these two events cannot be determined in advance. However, it is guaranteed that the removal from the `cluster.workers` list happens before the last `'disconnect'` or `'exit'` event is emitted. ```js import cluster from 'node:cluster'; for (const worker of Object.values(cluster.workers)) { worker.send('big announcement to all workers'); } ```

readonly



SCHED_NONE: number

readonly



SCHED_RR: number

Methods



disconnect(callback?: () => void): void



fork(env?: any): Worker

Spawn a new worker process. This can only be called from the primary process.

deprecated



setupMaster(settings?: ClusterSettings): void



setupPrimary(settings?: ClusterSettings): void

`setupPrimary` is used to change the default 'fork' behavior. Once called, the settings will be present in `cluster.settings`. Any settings changes only affect future calls to [`.fork()`](https://nodejs.org/docs/latest-v22.x/api/cluster.html#clusterforkenv) and have no effect on workers that are already running. The only attribute of a worker that cannot be set via `.setupPrimary()` is the `env` passed to [`.fork()`](https://nodejs.org/docs/latest-v22.x/api/cluster.html#clusterforkenv). The defaults above apply to the first call only; the defaults for later calls are the current values at the time of `cluster.setupPrimary()` is called. ```js import cluster from 'node:cluster'; cluster.setupPrimary({ exec: 'worker.js', args: ['--use', 'https'], silent: true, }); cluster.fork(); // https worker cluster.setupPrimary({ exec: 'worker.js', args: ['--use', 'http'], }); cluster.fork(); // http worker ``` This can only be called from the primary process.



addListener(event: string,
listener: (...args: any[]) => void,
): this

events.EventEmitter 1. disconnect 2. exit 3. fork 4. listening 5. message 6. online 7. setup



addListener(event: "disconnect",
listener: (worker: Worker) => void,
): this



addListener(event: "exit",
listener: (worker: Worker,
code: number,
signal: string,
) => void,
): this



addListener(event: "fork",
listener: (worker: Worker) => void,
): this



addListener(event: "listening",
listener: (worker: Worker,
address: Address,
) => void,
): this



addListener(event: "message",
listener: (worker: Worker,
message: any,
handle: net.Socket | net.Server,
) => void,
): this



addListener(event: "online",
listener: (worker: Worker) => void,
): this



addListener(event: "setup",
listener: (settings: ClusterSettings) => void,
): this



emit(event: string | symbol,
...args: any[],
): boolean



emit(event: "disconnect",
worker: Worker,
): boolean



emit(event: "exit",
worker: Worker,
code: number,
signal: string,
): boolean



emit(event: "fork",
worker: Worker,
): boolean



emit(event: "listening",
worker: Worker,
address: Address,
): boolean



emit(event: "message",
worker: Worker,
message: any,
handle: net.Socket | net.Server,
): boolean



emit(event: "online",
worker: Worker,
): boolean



emit(event: "setup",
settings: ClusterSettings,
): boolean



on(event: string,
listener: (...args: any[]) => void,
): this



on(event: "disconnect",
listener: (worker: Worker) => void,
): this



on(event: "exit",
listener: (worker: Worker,
code: number,
signal: string,
) => void,
): this



on(event: "fork",
listener: (worker: Worker) => void,
): this



on(event: "listening",
listener: (worker: Worker,
address: Address,
) => void,
): this



on(event: "message",
listener: (worker: Worker,
message: any,
handle: net.Socket | net.Server,
) => void,
): this



on(event: "online",
listener: (worker: Worker) => void,
): this



on(event: "setup",
listener: (settings: ClusterSettings) => void,
): this



once(event: string,
listener: (...args: any[]) => void,
): this



once(event: "disconnect",
listener: (worker: Worker) => void,
): this



once(event: "exit",
listener: (worker: Worker,
code: number,
signal: string,
) => void,
): this



once(event: "fork",
listener: (worker: Worker) => void,
): this



once(event: "listening",
listener: (worker: Worker,
address: Address,
) => void,
): this



once(event: "message",
listener: (worker: Worker,
message: any,
handle: net.Socket | net.Server,
) => void,
): this



once(event: "online",
listener: (worker: Worker) => void,
): this



once(event: "setup",
listener: (settings: ClusterSettings) => void,
): this



prependListener(event: string,
listener: (...args: any[]) => void,
): this



prependListener(event: "disconnect",
listener: (worker: Worker) => void,
): this



prependListener(event: "exit",
listener: (worker: Worker,
code: number,
signal: string,
) => void,
): this



prependListener(event: "fork",
listener: (worker: Worker) => void,
): this



prependListener(event: "listening",
listener: (worker: Worker,
address: Address,
) => void,
): this



prependListener(event: "message",
listener: (worker: Worker,
message: any,
handle?: net.Socket | net.Server,
) => void,
): this



prependListener(event: "online",
listener: (worker: Worker) => void,
): this



prependListener(event: "setup",
listener: (settings: ClusterSettings) => void,
): this



prependOnceListener(event: string,
listener: (...args: any[]) => void,
): this



prependOnceListener(event: "disconnect",
listener: (worker: Worker) => void,
): this



prependOnceListener(event: "exit",
listener: (worker: Worker,
code: number,
signal: string,
) => void,
): this



prependOnceListener(event: "fork",
listener: (worker: Worker) => void,
): this



prependOnceListener(event: "listening",
listener: (worker: Worker,
address: Address,
) => void,
): this



prependOnceListener(event: "message",
listener: (worker: Worker,
message: any,
handle: net.Socket | net.Server,
) => void,
): this



prependOnceListener(event: "online",
listener: (worker: Worker) => void,
): this



prependOnceListener(event: "setup",
listener: (settings: ClusterSettings) => void,
): this