Fátima Filipe Fátima Filipe - 4 months ago 47
Node.js Question

Cancel Regex match if timeout

Is it possible to cancel a

regex.match
operation if takes more than 10 seconds to complete?

I'm using an huge regex to match a specific text, and sometimes may work, and sometimes can fail...

regex:
MINISTÉRIO(?:[^P]*(?:P(?!ÁG\s:\s\d+\/\d+)[^P]*)(?:[\s\S]*?))PÁG\s:\s+\d+\/(\d+)\b(?:\D*(?:(?!\1\/\1)\d\D*)*)\1\/\1(?:[^Z]*(?:Z(?!6:\s\d+)[^Z]*)(?:[\s\S]*?))Z6:\s+\d+


Working example: https://regex101.com/r/kU6rS5/1

So.. i want cancel the operation if takes more than 10 seconds. Is it possible? I'm not finding anything related in sof

Thanks.

Answer

You could spawn a child process that does the regex matching and kill it off if it hasn't completed in 10 seconds. Might be a bit overkill, but it should work.

fork is probably what you should use, if you go down this road.

If you'll forgive my non-pure functions, this code would demonstrate the gist of how you could communicate back and forth between the forked child process and your main process:

index.js

const { fork } = require('child_process');
const processPath = __dirname + '/regex-process.js';
const regexProcess = fork(processPath);
let received = null;

regexProcess.on('message', function(data) {
  console.log('received message from child:', data);
  clearTimeout(timeout);
  received = data;
  regexProcess.kill(); // or however you want to end it. just as an example.
  // you have access to the regex data here.
  // send to a callback, or resolve a promise with the value,
  // so the original calling code can access it as well.
});

const timeoutInMs = 10000;
let timeout = setTimeout(() => {
  if (!received) {
    console.error('regexProcess is still running!');
    regexProcess.kill(); // or however you want to shut it down.
  }
}, timeoutInMs);

regexProcess.send('message to match against');

regex-process.js

function respond(data) {
  process.send(data);
}

function handleMessage(data) {
  console.log('handing message:', data);
  // run your regex calculations in here
  // then respond with the data when it's done.

  // the following is just to emulate
  // a synchronous computational delay
  for (let i = 0; i < 500000000; i++) {
    // spin!
  }
  respond('return regex process data in here');
}

process.on('message', handleMessage);

This might just end up masking the real problem, though. You may want to consider reworking your regex like other posters have suggested.