1 new chat request from a

1 new chat request from a-14

Pavel Ln -- 07-Sep-2012 pm -- hehehe Christina Bartkus -- 07-Sep-2012 pm -- and this is how Urban Legend came about. Sean Wheeler -- 07-Sep-2012 pm -- People that don't get this need to kit puberty sooner.

Adam David Belle -- 07-Sep-2012 pm -- I fail to see where this is funny.

The naive implementation of sending a notification to all friends whenever a user comes online or goes offline has a worst case cost of O(average friendlist size * peak users * churn rate) messages/second, where churn rate is the frequency with which users come online and go offline, in events/second.

This is wildly inefficient to the point of being untenable, given that the average number of friends per user is measured in the hundreds, and the number of concurrent users during peak site usage is on the order of several millions.

The method we chose to get text from one user to another involves loading an iframe on each Facebook page, and having that iframe's Javascript make an HTTP GET request over a persistent connection that doesn't return until the server has data for the client.