在 Promise 被拒绝后停止运行个进程

Question

我正在使用以下工作正常的代码，但问题是当我遇到错误时，我希望它停止所有其他承诺。例如，如果 chi.getCommand(val1, val2)，将发送拒绝并且我遇到了异常捕获，我想取消对 chss.exe 和 app.getStatus(12); 的承诺，我该如何实现？

  var start = Promise.all([
      chi.getCommand(val1, val2),
      chi.findAndUpdateCustomer()
    ]).spread(function (command, customer) {
        return chss.exe(runnableDoc, command, customer)
                 .delay(10)
                 .then(function (val) {
                   if (val) console.log(val);
                   return app.getStatus(12);
                 });
    }).catch(function (err) {
        // catch and handle errors and when it come to here I want it to stops all the chain above
    });

这是获取命令的代码：

function getCommand(method, cmd) {
  return new Promise(function (resolve, reject) {
    ...
    child.stderr.on('data', function (data) {
        console.log('stderr: here!' + data);
        reject(data);
    });
}

控制台日志 stderr: 此处！ 已打印，因此调用了解析！

更新1

唯一停止 getStatus 的是当我输入 process.exit(1) 但这会杀死所有进程，我只想停止函数 getCommand 的所有链，以防我 到达到 catch 块,

is there a way?

is it bug in blueBird ? I use "bluebird": "2.9.34"

函数getCommand（方法，命令）{ return 新的承诺（函数（解决，拒绝）{

var spawn = require('child_process').spawn;
var ls = spawn("cmdbug",["/c","npm install express --save"]);


    ls.on('error', function (err) {
        console.log(err);
        reject(err);
    });

我得到的错误是

{ [Error: spawn cmdr ENOENT] code: 'ENOENT', errno: 'ENOENT', syscall: 'spawn cmdbug', path: 'cmdr', spawnargs: [ '/g', 'npm install express --save' ] } { [Error: spawn cmdbug ENOENT] code: 'ENOENT', errno: 'ENOENT', syscall: 'spawn cmdbug', path: 'cmdr', spawnargs: [ '/g', 'npm install express --save' ] } Child process failed with code -4058

并且 getStatus 的进程仍在写入控制台。

我使用但不用于测试的代码是：

getCommand 是抛出 错误的函数！

var start= function () {
    return new Promise.all([
        childP.getChildProcessCommand(val1, val2),
        childP.findAndUpdateCustomer()
    ]).spread(function (cmd, updated) {
            //Execute child process
            return Promise.all([
                childP.getCommand('spawn', cmd),
                app.getStatus(51000,10,1);
            ]).catch(function (err) {
                // catch and handle errors
                console.log("An error occur: " + err);
                return;
            })
        }).catch(function (err) {
            // catch and handle errors
            console.log("An error occur: " + err);
            return;
        })
}();

查询状态代码为：

// Returns a promise that resolves when the port is open

checkPortStatus: function(port, host){
  return new Promise((resolve, reject) => {
    portscanner.checkPortStatus(port, host, function(error, status) {
      if(error)
        reject(error);
      else if(status === 'open')
        resolve(status);
      else
        reject(new Error('Port is not open'));
    });
  });
},

// THE API function
getStatus: function(port, retriesLeft) {

  const TIME_BETWEEN_CHECKS = 1000;
  const HOST = '127.0.0.1';
  const RETRIES = 20;
  retriesLeft = retriesLeft === void 0 ? RETRIES : retriesLeft;

  if(!port) throw new Error('Port is required');
  if(retriesLeft === 0) Promise.reject('Timed Out');

  return new Promise((resolve, reject) => {

    // If it rejects, we do added work.
    this.checkPortStatus(port, host).then(resolve, error => {
     console.log("Waiting for port " + port + " attempt: " + retry);
      setTimeout(() => {

        this.getStatus(port, retriesLeft - 1).then(resolve, reject);

      }, TIME_BETWEEN_CHECKS);
    });
  });
}

And I see the error in the console and still see the console log of the following for 10 attempts. console.log("Waiting for port " + port + " attempt: " + retry);

更新2 当尝试更改时 @artur 在第二个选项中建议我在递归调用中遇到错误错误是：

TypeError: Cannot read property 'then' of undefined

这是我试过的：

getStatus: function(port, retriesLeft) {

  const TIME_BETWEEN_CHECKS = 1000;
  const HOST = '127.0.0.1';
  const RETRIES = 20;
  retriesLeft = retriesLeft === void 0 ? RETRIES : retriesLeft;

  if(!port) throw new Error('Port is required');
  if(retriesLeft === 0) Promise.reject('Timed Out');

  var promise = new Promise((resolve, reject) => {

    // If it rejects, we do added work.
    this.checkPortStatus(port, host).then(resolve, error => {
     console.log("Waiting for port " + port + " attempt: " + retry);
      setTimeout(() => {
        //The error in the following recursive call
        this.getStatus(port, retriesLeft - 1).then(resolve, reject);

      }, TIME_BETWEEN_CHECKS);
      }).catch(function (error) {
         return reject(error);
     });
        return {
            promise:promise,
    cancel: function() {
        console.log('cancelling');
        clearTimeout(token);
        }

       }
    });
  });
}

Answer 1

好吧，在您的实际代码（来自 UPDATE1 的代码）中，您是运行ning getCommand 同时到 getStatus，而不是按顺序。您在子进程失败之前调用（启动）它们两个，当它失败时，没有任何东西会停止 getStatus.

就像在您的第一个片段中一样将它们链接在一起，其中 getCommand 中的拒绝将导致 getStatus 根本不会运行。您可以使用

childP.getCommand('spawn', cmd)
.timeout(5000)
.then(function(cmdresult) {
    return app.getStatus(51000, 10, 1);
}).catch(function (err) {
    console.log("An error occured: " + err);
});

Answer 2

正如@Esailija 指出的那样，bluebird 内置了取消机制——这非常好，而且对于简单的异步计算来说，完全没问题。

Promise.config({
  cancellation: true
});

function createCancellableMock(result, time) {

  return new Promise(function(resolve, reject, onCancel) {

    // var child = runCommand();
    var token = setTimeout(function() {
      if (result) {
        console.log('almost done', result);
        resolve(result);
      } else {
        reject('_ERR_');
      }
    }, time);

    onCancel(function() {
      console.log('cancelling');
      // child.kill('SIGTERM');
      clearTimeout(token);
    })
  })

}

var op1 = createCancellableMock('ok-1', 1000);
//var op2 = createCancellableMock('ok-2', 500);
var op2 = createCancellableMock(null, 500); // will be rejected

Promise.all([op1, op2])
  .spread(function(v1, v2) {
    console.log('BOTH-OK', v1, v2)
  })
  .catch(function() {
    console.error('ERROR');
    op1.cancel();
  })
  .finally(function() {
    console.log('finally');
  })

<script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.3.0/bluebird.core.js"></script>

更新

您可以取消递归定义的操作（例如重试）。在这种情况下，最好的策略是不要将动作本身与递归行为混为一谈。在下面的代码片段中，我创建了一个非常简单的包装器来说明我的观点。

var TOO_MANY_RETRIES_ERROR = 'too_many_retries_error';
var PROB_OF_FAIL = 0.8;
var INTERVAL = 200;
var RETRIES = 5;

var CANCEL_AFTER = null;
//var CANCEL_AFTER = INTERVAL * (RETRIES/2);

Promise.config({
  cancellation: true
});

function retryWithCancel(params) {

  // params = {op - operation to retry (it should return a promise, which either ),
  // interval - between retries, retries - number of retries }

  console.log('running, retries left ', params.retries);

  params = Object.assign({}, params); // copy params - no side-effects please
  params.retries--;
  if (params.retries <= 0) {
    console.error('too many retries');
    return Promise.reject(new Error(TOO_MANY_RETRIES_ERROR));
  }

  return new Promise(function(resolve, reject, onCancel) {

    var o = params.op()
      .catch(function() {
        return Promise.delay(params.interval)
          .then(retryWithCancel.bind(null, params))
          .catch(reject)
      })
      .then(resolve)


    onCancel(function() {
      console.log('Cancelling, retries left: ', params.retries);
      o.cancel();
    });

  })

}

function fakeOperation() {

  return Promise.delay(100)
    .then(function() {
      if (Math.random() > PROB_OF_FAIL) {
        return Promise.resolve('SUCCESS');
      } else {
        return Promise.reject(new Error('ERROR'));
      }

    })
}

var p = retryWithCancel({
    op: fakeOperation,
    interval: INTERVAL,
    retries: RETRIES
  })
  .then(console.log.bind(console))
  .catch(console.error.bind(console))
  .finally(console.log.bind(console, 'done'))

if (CANCEL_AFTER) {
  setTimeout(function() {
    p.cancel();
  }, CANCEL_AFTER)
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.3.1/bluebird.js"></script>

原始答案

总的来说，承诺很好，但它们不提供开箱即用的取消机制。在某些情况下（例如 https://github.com/whatwg/fetch/issues/27）这是一个很大的问题，在您的情况下，取消选项也非常方便。唯一有效的选择是自己添加。

基于承诺的基本解决方案

我将问题提炼到最低限度，并使其在浏览器中可运行。以下方法的缺点是取消后承诺永远不会 resolve 也不会 reject - 通常情况下肯定是 unacceptable。或者 .cancel 可能会拒绝带有某些特殊符号的承诺。这些方法都不优雅。

function createCancellableMock(result, time) {
    
    // child = null;
    var token = null ;
    var p = new Promise(function(resolve, reject) {
        
        // child = runCommand();
        token = setTimeout(function() {
            if (result) {
                console.log('almost done', result);
                resolve(result);
            } 
            else {
                reject('_ERR_');
            }
        }, time);
    }
    )
    
    return {
        promise: p,
        cancel: function() {
            console.log('cancelling');
            // child.kill('SIGTERM');
            clearTimeout(token);
        }
    }
}

var op1 = createCancellableMock('ok-1', 1000);
// var op2 = createCancellableMock('ok-2', 500);
var op2 = createCancellableMock(null, 500); // will be rejected

Promise.all([op1.promise, op2.promise])
.then(function(vs) { // no spread in native implemantation
    console.log('BOTH-OK', vs[0], vs[1])
})
.catch(function() {
    console.error('ERROR');
    op1.cancel();
})

基于可观察的解决方案

对于基本的操作顺序，promises 很好，但是有一种更高级的方法可用：即 observables。它们不仅提供内置的取消/处置机制，而且允许处理发出的多个值并在非常严格的控制下保持复杂的异步执行。

  function createCancellableMock(result, time) {

    return Rx.Observable.create(function(observer) {

      var done = false;
      var token = setTimeout(function() {
        if (result) {
          console.log('almost done: ' + result);
          observer.onNext(result);
          observer.onCompleted();
        } else {
          observer.onError('_ERR_');
        }
      }, time);

      // this will be called upon `disposed`
      return function() {
        console.log('disposing, done: ', done);
        if (!done) {
          clearTimeout(token);
        }
      }

    })

  }

  var op1 = createCancellableMock('ok-1', 1000);
  //var op2 = createCancellableMock('ok-2', 500);
  var op2 = createCancellableMock(null, 500); // will be rejected

  op1.zip(op2)
    .catch(function(err) {
      // it was disposed automatically :) hurray
      console.log('Caught', err);
      // return Rx.Observable.empty(); // swallowing
      return Rx.Observable.throw(err); // throwing

    })
    .subscribe(function(vs) {
        console.log('BOTH-OK', vs[0], vs[1])
      },
      function(err) {
        console.error('Unhandled error', err);
      },
      function() {
        console.log('Upon successful termination.')
      }
    );

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/4.0.7/rx.all.js"></script>

在 Promise 被拒绝后停止运行个进程

Stop running processes after a Promise is rejected

javascript

node.js

promise

bluebird

更新

原始答案

基于承诺的基本解决方案

基于可观察的解决方案

在 Promise 被拒绝后停止 运行 个进程

Stop running processes after a Promise is rejected

javascript

node.js

promise

bluebird

更新

原始答案

基于承诺的基本解决方案

基于可观察的解决方案

在 Promise 被拒绝后停止运行个进程