Async call from within a Meteor server side method.

async.js

if (Meteor.isServer) {
  var Fiber = Npm.require('fibers');

  function async (cb) {
    Meteor.setTimeout(function () {
      cb(null, 'hello');
    }, 3000);
  }

  Meteor.methods({
    callAsync: function () {
      var fiber = Fiber.current;

      var fence = Meteor._CurrentWriteFence.get()
        , handle = fence && fence.beginWrite();

      async(function (err, res) {
        handle && handle.committed();
        fiber.run(res);
      });

      return Fiber.yield();
    }
  });
}

if (Meteor.isClient) {
  testCallAsync = function () {
    Meteor.call('callAsync', function (err, res) {
      if (err) console.log(err);
      else console.log('response: ', res);
    });
  };
}