Does a before_filter in the application controller slow down the app?

Question

I have a few before_filter in my application controller to check 1) If the current_user is banned, 2) If the current_user has received a new message and 3) If the current_user has any pending friend requests.

This means that before every request the app will check for these things. Will this cause server issues in the future, possible a server overload?

Answer 1

I wouldn't definitely say that it would create a server overload on it's own, for a server overload you need many concurrent requests and rails have a connection pool to the database out of the box, but this will slow down the process as you have 3 queries before each request is even at the controller to do what it was intended to do.

Facebook solved this at 2009 using what they called BigPipe, it is not a new technology rather it is leveraging the browsers and the ability to send a few requests with fragmented parts of the page and only then compose it using some Javascript.

You can have a read here http://www.facebook.com/note.php?note_id=389414033919 .

As for your check if the user is banned, yes that is something you'd have to check either way, perhaps you can have this in cache using memcached or redis so it won't hit your database directly every time.