节点 - 以 class 形式编写子进程生成执行

Question

我正在重写一个生成子进程并执行命令的现有模块。

我已将其重写为 class 但是当我运行代码时，我收到一个错误，指出 Promise rejects 和 resolve are undefined。我假设我将它们错误地传递给了 .call 方法，但我没有找到可以传递它们的不同方法。

代码如下：

import logger from './logger.utils';
import { spawn, ChildProcess } from 'child_process';

/**
 * This function runs a spawn command and rejects the promise if timed out
 * @param cmd - the command to execute
 * @param params - the command's parameters
 * @param timeoutMs - timeout in milliseconds
 * @param taskDescription - a text description of the task for logging
 */
export class SpawnTimeout {
  cmd: string;
  params: string[];
  finished: boolean;
  childProcess: ChildProcess;
  timeoutMs: number;
  timeout: NodeJS.Timeout;
  taskDescription: string;
  handlers: Object;

  constructor(
    cmd: string,
    params: string[],
    timeoutMs: number,
    taskDescription: string = 'no description specified'
  ) {
    this.finished = false;
    this.childProcess = spawn(cmd, params, {
      stdio: [process.stdin, process.stdout, process.stderr],
    });
    this.timeoutMs = timeoutMs;
    this.timeout = null;
    this.taskDescription = taskDescription;
    this.cmd = cmd;
    this.params = params;
  }
  exec() {
    return new Promise((resolve, reject) => {
      const handlers = {
        resolve,
        reject,
      };
      this.handlers = handlers;
      this.childProcess.once('error', this._onError.call(this.handlers));
      this.childProcess.once('exit', this._onExit.call(this.handlers));
      this.timeout = setTimeout(this._setTimeout, this.timeoutMs);
    });
  }
  _onError(err: Error, handlers) {
    clearTimeout(this.timeout);
    const message = `spawn [${this.taskDescription}] ${this.cmd}, ${this.params} failed with error ${err}`;
    logger.error(message);
    handlers.reject(new Error(message));
  }

  _onExit(code: number, handlers) {
    this.finished = true;
    clearTimeout(this.timeout);
    logger.debug(`spawn [${this.taskDescription}] finished.code ${code}`);
    if (code == 0) {
      handlers.resolve(true);
    }
    // case of error, code !== 0
    const message = `spawn [${this.taskDescription}] cmd : ${this.cmd} ${this.params}. failed with code ${code}`;
    logger.error(message);
    handlers.reject(new Error(message));
  }

  _setTimeout() {
    if (!this.finished) {
      logger.warn(
        `spawn [${this.taskDescription}] - timeout. cmd : ${this.cmd}, ${this.params}`
      );
      this.childProcess.kill();
    }
  }
}

调用handlers.resolve或handlers.reject时出现错误。

请告知我该如何解决这个问题？或者即使这样的实施良好做法。

Answer 1

call 立即调用一个函数，第一个参数是 this 调用函数的上下文，在这种情况下它不是 return 函数并且它是不正确的提供结果作为 once.

的侦听器

回调需要用函数包装以提供预期参数：

this.childProcess.once('error', err => this._onError(err, this.handlers))
this.childProcess.once('exit', code => this._onExit(code, this.handlers));

由于回调必然会以这种方式纠正 this，因此可能没有必要将 this.handlers 传递给它们，因为它已经在它们内部可用。

节点 - 以 class 形式编写子进程生成执行

Node - write child process spawn execution in class form

node.js

child-process

spawn