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Timers in the Window context prevent Node.js process from exit and window object from GC clean-up

See original GitHub issue

If FetchExternalResources and ProcessExternalResources contain 'script' and page scripts set timers, Node.js process does not exit.

Test code 1 (page scripts with some possible timers are under user’s control):

const jsdom = require('jsdom');

jsdom.env({
  html: `
    <!doctype html>
    <html>
      <head>
        <meta charset="UTF-8">
        <title></title>
      </head>
      <body>
        <script>
          window.document.title = 'Scripted Title';
          window.setInterval(() => {}, 1000);
        </script>
      </body>
    </html>
  `,
  done: (err, window) => {
    console.log(window.document.title);
  },
  features: {
    FetchExternalResources: ['script'],
    ProcessExternalResources: ['script']
  },
});

After logged output the script just freezes. However, if all timers are cleaned up, the script exits properly:

const jsdom = require('jsdom');

jsdom.env({
  html: `
    <!doctype html>
    <html>
      <head>
        <meta charset="UTF-8">
        <title></title>
      </head>
      <body>
        <script>
          window.document.title = 'Scripted Title';
          window.setInterval(() => {}, 1000);
        </script>
      </body>
    </html>
  `,
  done: (err, window) => {
    console.log(window.document.title);

    let id = window.setTimeout(() => {}, 0);
    console.log(id);
    while (id) {
      window.clearTimeout(id);
      id--;
    }

    id = window.setInterval(() => {}, 0);
    console.log(id);
    while (id) {
      window.clearInterval(id);
      id--;
    }
  },
  features: {
    FetchExternalResources: ['script'],
    ProcessExternalResources: ['script']
  },
});

Test code 2 (page scripts with many timers are beyond easy user’s control):

const jsdom = require('jsdom');

jsdom.env({
  url: 'http://www.nytimes.com/',
  done: (err, window) => {
    console.log(window.document.title);
  },
  features: {
    FetchExternalResources: ['script'],
    ProcessExternalResources: ['script']
  },
});

After logged output the script just freezes as well. And if all timers are cleaned up, the script exits properly too:

const jsdom = require('jsdom');

jsdom.env({
  url: 'http://www.nytimes.com/',
  done: (err, window) => {
    console.log(window.document.title);

    let id = window.setTimeout(() => {}, 0);
    console.log(id);
    while (id) {
      window.clearTimeout(id);
      id--;
    }

    id = window.setInterval(() => {}, 0);
    console.log(id);
    while (id) {
      window.clearInterval(id);
      id--;
    }
  },
  features: {
    FetchExternalResources: ['script'],
    ProcessExternalResources: ['script']
  },
});

Issue Analytics

State:
Created 7 years ago
Comments:5 (5 by maintainers)

Top GitHub Comments

1reaction

domeniccommented, May 24, 2016

There’s no way to execute code in the future without keeping the process in which that code will execute alive. So documenting seems like the way to go here.

0reactions

vsemozhetbytcommented, May 25, 2016

Well, I am not a native English speaker and my English is bad, so maybe I should not suggest a large amount of the text. However, something like that (with your additions and corrections) may be helpful:

It should be taken into consideration, that timers in the page scripts (set by window.setImmediate(), window.setInterval() and window.setTimeout()) could prevent window object from being GC-ed and thereby could cause memory leaks. These timers also could interfere with main process eventloop and prevent the script from natural exit after eventloop drain. To mitigate these risks, window.close() should be called after each document processing completion if page scripts execution is activated.

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