What happens in node.js when you start a setInterval(), but do some synchronous work? setInterval() calls get dropped.

output.txt

2015-03-23T19:41:49.232Z
2015-03-23T19:41:49.367Z
2015-03-23T19:41:49.470Z
2015-03-23T19:41:49.571Z
sync task start
sync task done
2015-03-23T19:41:50.632Z
2015-03-23T19:41:50.733Z
2015-03-23T19:41:50.834Z
^C

skipped_setInterval.js

setInterval(function() {
  var now = new Date();
  console.log(now.toJSON());
}, 100);

setTimeout(function() {
  var start = new Date();
  var now = new Date();

  console.log('sync task start');
  while (now.getTime() - start.getTime() < 1000) {
    now = new Date();
  }
  console.log('sync task done');
}, 500)

Why would callbacks being called out of order? I assumed it was a single thread model, so the callbacks should be executed off one stack.

If callbacks can be called out of order, that would make shared state more difficult to manage.