According to this article here:
https://dweldon.silvrback.com/common-mistakes
Subscriptions don\'t block
Many aspects of the frame
Maybe I don't get the question, but the Meteor.Subscribe function has callbacks named onError and onReady methods.
Optional. May include onError and onReady callbacks. If a function is passed instead of an object, it is interpreted as an onReady callback.
From docs.
For example.
Meteor.subscribe("posts", {
onReady: function () { console.log("onReady And the Items actually Arrive", arguments); },
onError: function () { console.log("onError", arguments); }
});
Also check this GitHub issue