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| | | /** |
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| | | * Clusters of Node.js processes can be used to run multiple instances of Node.js |
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| | | * that can distribute workloads among their application threads. When process isolation |
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| | | * is not needed, use the [`worker_threads`](https://nodejs.org/docs/latest-v25.x/api/worker_threads.html) |
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| | | * module instead, which allows running multiple application threads within a single Node.js instance. |
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| | | * |
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| | | * The cluster module allows easy creation of child processes that all share |
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| | | * server ports. |
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| | | * |
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| | | * ```js |
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| | | * import cluster from 'node:cluster'; |
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| | | * import http from 'node:http'; |
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| | | * import { availableParallelism } from 'node:os'; |
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| | | * import process from 'node:process'; |
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| | | * |
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| | | * const numCPUs = availableParallelism(); |
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| | | * |
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| | | * if (cluster.isPrimary) { |
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| | | * console.log(`Primary ${process.pid} is running`); |
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| | | * |
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| | | * // Fork workers. |
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| | | * for (let i = 0; i < numCPUs; i++) { |
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| | | * cluster.fork(); |
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| | | * } |
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| | | * |
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| | | * cluster.on('exit', (worker, code, signal) => { |
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| | | * console.log(`worker ${worker.process.pid} died`); |
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| | | * }); |
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| | | * } else { |
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| | | * // Workers can share any TCP connection |
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| | | * // In this case it is an HTTP server |
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| | | * http.createServer((req, res) => { |
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| | | * res.writeHead(200); |
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| | | * res.end('hello world\n'); |
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| | | * }).listen(8000); |
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| | | * |
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| | | * console.log(`Worker ${process.pid} started`); |
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| | | * } |
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| | | * ``` |
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| | | * |
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| | | * Running Node.js will now share port 8000 between the workers: |
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| | | * |
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| | | * ```console |
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| | | * $ node server.js |
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| | | * Primary 3596 is running |
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| | | * Worker 4324 started |
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| | | * Worker 4520 started |
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| | | * Worker 6056 started |
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| | | * Worker 5644 started |
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| | | * ``` |
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| | | * |
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| | | * On Windows, it is not yet possible to set up a named pipe server in a worker. |
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| | | * @see [source](https://github.com/nodejs/node/blob/v25.x/lib/cluster.js) |
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| | | */ |
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| | | declare module "node:cluster" { |
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| | | import * as child_process from "node:child_process"; |
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| | | import { EventEmitter, InternalEventEmitter } from "node:events"; |
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