The return pipe does not close

Question

I use sax-js to read large xml files. I can not get the program to exit when the parser is finished. Here is a script form with parser logic removed.

    var fs = require('fs');
    var sax = require('sax');

    var feedFile = 'foo.xml';
    var saxStream = sax.createStream(true)
    .on('opentag', function(node) { // do stuff })
    .on('end', function() {
         console.log("parser end event");
    });

    var options = {
         flags: 'r',
         encoding: 'utf8',
         mode: 0666,
         bufferSize: 1024
    };

    fs.createReadStream(feedFile, options, function(err) {
        throw err;
    })
    .on('end', function() {
        console.log("read stream end event");
    })
    .pipe(saxStream);

Everything is working correctly. And the console receives messages like this

    read stream end event
    parser end event

And then the process should exit. Is not. What am I missing?

---

EDIT: What I miss. There was a resource still open so that node could not exit. The temptation is to start trying to call process.exit () anywhere, anywhere. I tried it myself in this case, and it broke the material.

My script was unable to exit because I had an open mongodb connection (managed by mongoose). Here, essentially (not in detail), what is fixed:

    saxStream.on('end', function() {
        console.log("parser end event");
        mongoose.disconnect();
    };