创建取消按钮...如何在Node / Express.js中完全中止请求

Question

我想在我的应用中创建一个“取消”按钮。该按钮要取消的请求包含Promise.all，由于另一端的API速率限制，通常需要几分钟才能完成。

如果我有这样的路线：

router.get('/api/my_route', (req, res, next) => {

//imagine this takes about 2 minutes to complete and send back the 200.
//The user changes their mind and wants to cancel it at the 1 minute mark.

  fetch("https://jsonplaceholder.typicode.com/albums")
    .then(first_response => first_response.json())
    .then(arr => Promise.all(arr.map(item => 
       fetch("https://jsonplaceholder.typicode.com/users")
       .then(second_response => second_response.json())
       .then(value => console.log(value))
      )))
    .then(() => {
        res.status(200);   
    });
});

如何取消此操作并在发出Promise请求时完全中止？

Answer 1

您将使用AbortController中止获取请求并在请求上侦听close事件以了解客户端关闭连接：

router.get('/api/my_route', (req, res, next) => {
  // we create a new AbortController to abort the fetch request
  const controller = new AbortController();
  const signal = controller.signal;

  req.on('close', err => { // if the request is closed from the other side
    controller.abort(); // abort our own requests
  })


  fetch("https://jsonplaceholder.typicode.com/albums", {signal})
    .then(first_response => first_response.json())
    .then(arr => Promise.all(arr.map(item => 
       fetch("https://jsonplaceholder.typicode.com/users", {signal})
       .then(second_response => second_response.json())
       .then(value => console.log(value))
      )))
    .then(() => {
        res.status(200);
    });
});

Answer 2

承诺本身没有取消机制。您可能会向远程服务器发送另一个api请求以取消原始请求，但如果它的速率有限，则表明它是一个可能不容易更改的旧服务器。