@stryker-mutator/core/src/concurrent/concurrency-token-provider.ts

import os from 'os';

import { StrykerOptions } from '@stryker-mutator/api/core';
import { ReplaySubject, Observable, range } from 'rxjs';
import { Disposable, tokens } from 'typed-inject';
import { commonTokens } from '@stryker-mutator/api/plugin';
import { Logger } from '@stryker-mutator/api/logging';

export class ConcurrencyTokenProvider implements Disposable {
  private readonly concurrencyCheckers: number;
  private readonly concurrencyTestRunners: number;
  private readonly testRunnerTokenSubject = new ReplaySubject<number>();

  public get testRunnerToken$(): Observable<number> {
    return this.testRunnerTokenSubject;
  }
  public readonly checkerToken$: Observable<number>;
  public static readonly inject = tokens(commonTokens.options, commonTokens.logger);

  constructor(options: Pick<StrykerOptions, 'checkers' | 'concurrency'>, private readonly log: Logger) {
    const cpuCount = os.cpus().length;
    const concurrency = options.concurrency ?? (cpuCount > 4 ? cpuCount - 1 : cpuCount);
    if (options.checkers.length > 0) {
      this.concurrencyCheckers = Math.max(Math.ceil(concurrency / 2), 1);
      this.checkerToken$ = range(this.concurrencyCheckers);
      this.concurrencyTestRunners = Math.max(Math.floor(concurrency / 2), 1);
      log.info('Creating %s checker process(es) and %s test runner process(es).', this.concurrencyCheckers, this.concurrencyTestRunners);
    } else {
      this.concurrencyCheckers = 0;
      this.checkerToken$ = range(1); // at least one checker, the `CheckerFacade` will not create worker process.
      this.concurrencyTestRunners = concurrency;
      log.info('Creating %s test runner process(es).', this.concurrencyTestRunners);
    }
    Array.from({ length: this.concurrencyTestRunners }).forEach(() => this.testRunnerTokenSubject.next(this.tick()));
  }

  public freeCheckers(): void {
    if (this.concurrencyCheckers > 0) {
      this.log.debug('Checking done, creating %s additional test runner process(es)', this.concurrencyCheckers);
      for (let i = 0; i < this.concurrencyCheckers; i++) {
        this.testRunnerTokenSubject.next(this.tick());
      }
      this.testRunnerTokenSubject.complete();
    }
  }

  private count = 0;
  private tick() {
    return this.count++;
  }

  public dispose(): void {
    this.testRunnerTokenSubject.complete();
  }
}