render complicated xml file

[mcgradycchen]

Hi Albanm,

We got a issue. Sometimes our xml file is very complicated, the apply sync function will run more than 30 minutes and makes 100% cpu.

Is there a way to abort the apply function with a timeout parameter or how can I implement this request?

Thanks

[albanm]

Hello,

I don't think it is possible to abort a running function. Did you try the async function ? It will not shorten the time but it will free the main event loop and allow you to set your own timeout, something like this (not tested):

function(callback) {
  aborted = false;
  var timeout = setTimeout(function() {
    aborted = true;
    callback(new Error('libxslt timeout'));
  }, 1000);
  stylesheet.apply(..., function(err, result) {
    if (!aborted) {
      clearTimeout(timeout);
      callback(err, result);
    }
  });
}

This is probably ok only if you don't care much about load as the task will still be running in the background and occupying a thread.

Another, probably saner solution is to analyze summarily the xml input (string length ? number of nodes ?) before running libxslt.

[mcgradycchen]

Hi Albanm,

Thanks for your reply.

The timeout solution looks good, but the task still be running is unacceptable.

I'm not familiar with Libxmljs.
Would you like to tell me how can I summary the xml nodes or the depth ?

Thanks~

[albanm]

Actually I am not that familiar with it myself. I guess something like this would work to count the nodes:

doc.find('//*').length

But is it going to be efficient on a very large document ? I don't know. Maybe the document string length is a good enough estimate ?

[gagern]

Does your conversion have to happen in a process that lives on, or could you create a process just for the conversion, and kill said process if the conversion takes too long? That would be the most robust way of doing this, I think.

[rainabba]

@mcgradycchen The issue you're having isn't specific to this library though. You'll want to learn how to setup new tasks/processes and control them to deal with that timeout scenario. Check out "Killing/Stopping the command" at http://krasimirtsonev.com/blog/article/Nodejs-managing-child-processes-starting-stopping-exec-spawn

Basically, you'll want to make a module that has your task (which needs to be run, but needs to be cancelable also) and launch a new process which runs that task (and can be killed).