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getMaxWorkers.ts
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getMaxWorkers.ts
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/**
* Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
import {cpus} from 'os';
import type {Config} from '@jest/types';
export default function getMaxWorkers(
argv: Partial<
Pick<Config.Argv, 'maxWorkers' | 'runInBand' | 'watch' | 'watchAll'>
>,
defaultOptions?: Partial<Pick<Config.Argv, 'maxWorkers'>>,
): number {
if (argv.runInBand) {
return 1;
} else if (argv.maxWorkers) {
return parseWorkers(argv.maxWorkers);
} else if (defaultOptions && defaultOptions.maxWorkers) {
return parseWorkers(defaultOptions.maxWorkers);
} else {
// In watch mode, Jest should be unobtrusive and not use all available CPUs.
const numCpus = cpus() ? cpus().length : 1;
const isWatchModeEnabled = argv.watch || argv.watchAll;
return Math.max(
isWatchModeEnabled ? Math.floor(numCpus / 2) : numCpus - 1,
1,
);
}
}
const parseWorkers = (maxWorkers: string | number): number => {
const parsed = parseInt(maxWorkers.toString(), 10);
if (
typeof maxWorkers === 'string' &&
maxWorkers.trim().endsWith('%') &&
parsed > 0 &&
parsed <= 100
) {
const numCpus = cpus().length;
const workers = Math.floor((parsed / 100) * numCpus);
return workers >= 1 ? workers : 1;
}
return parsed > 0 ? parsed : 1;
};