NodeJS：如何运行正确并行生成？

Question

我是运行一个 for 循环，其中执行以下内容：

let perform_vrp = function() {
    //..
    perform_tsp();
}

let perform_tsp = function() {
  //..

  const pyProg = spawn('python3', [process.env.PWD + '/server/vrp_solver/tsp_solver.py', '/../../route_data/' + depot.city + '/' + moment(route.date_driven).format('Y-MM-DD'), 'morning',route.name]);

  winston.info('Solving the TSP for %s...', route.name);

  pyProg.stdout.on('data', function (data) {

    let result_string = data.toString();
    winston.info('Route result for %s is: %s', route.name, result_string);

    let result_array = eval(result_string); 
    //...
  });
}

它基本上为 for 循环中的每个项目调用一个 python 脚本。

然而，当一个脚本完成后，它也会完成所有其他脚本，并继续使用标准输出，并为 for 循环中的所有项目使用相同的 'data'。

如何防止这种情况发生并让 stdout 等待正确的子进程完成？

更新：

以上是通过以下命令触发的：

const winston = require('../../server/winston');
const perform_vrp = require('../../server/modules/vrp');
const moment = require('moment');
const Utils = require('../modules/utils');
let utils = new Utils();

let do_vrp = async function(next_delivery_date, cities) {
  winston.info('Generating routes for %s', next_delivery_date);
  for (let index in cities) {
    if (cities.hasOwnProperty(index)) {
      let city = cities[index];
      winston.info('Generating route for %s on %s', city, next_delivery_date);
      await perform_vrp(next_delivery_date,[city]);
      await utils.sleep(60000);
    }
  }
};


let process_routes = async function() {

  //...

  let morning_cities = ['Boston','Chicago'];
  await do_vrp(next_delivery_date.format('YYYY-MM-DD'), morning_cities);
};

process_routes();

Answer 1

问题是您在 for 循环中使用 await 来等待脚本完成，但您没有将脚本的执行包装在 Promise.[=14 中=]

在perform_tsp

在 data 事件触发时解析的 Promise 中的 spawn 和事件，并用接收到的数据解析，如下所示：

  let perform_tsp = function () {
  //..
  return new Promise((resolve, reject) => {
    const pyProg = spawn('python3', [process.env.PWD + '/server/vrp_solver/tsp_solver.py', '/../../route_data/' + depot.city + '/' + moment(route.date_driven).format('Y-MM-DD'), 'morning', route.name]);
    winston.info('Solving the TSP for %s...', route.name);
    pyProg.stdout.on('data', function (data) {
      resolve(data);
    })
  });
}

在perform_vrp

只是 return 来自 perform_tsp 的 returned 承诺，因此您可以在 for 循环中等待它：

let perform_vrp = function () {
  //..
  return perform_tsp();
}

在do_vrp

接收 resolved promise 的数据，即 spawn 的数据，之后您可以执行 data 事件回调中的逻辑：

 let do_vrp = async function (next_delivery_date, cities) {
  winston.info('Generating routes for %s', next_delivery_date);
  for (let index in cities) {
    if (cities.hasOwnProperty(index)) {
      let city = cities[index];
      winston.info('Generating route for %s on %s', city, next_delivery_date);
      let data = await perform_vrp(next_delivery_date, [city]);
      let result_string = data.toString();
      winston.info('Route result for %s is: %s', route.name, result_string);
      let result_array = eval(result_string);
      await utils.sleep(60000);
    }
  }
};

之前的结构会运行如果你想重新并行生成生成Promise.allapi.

  let do_vrp = async function (next_delivery_date, cities) {
  winston.info('Generating routes for %s', next_delivery_date);

  const promises = cities.map((city) => {
    return perform_vrp(next_delivery_date, [city]);
  });

  const results = await Promise.all(promises);
  results.forEach((data) => {
    winston.info('Generating route for %s on %s', city, next_delivery_date);
    let result_string = data.toString();
    winston.info('Route result for %s is: %s', route.name, result_string);
    let result_array = eval(result_string);
  });
};

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