why not to use thread.sleep for no reason, and explain it to a programmer

Question

While passing through code in our project I came across a web method that had this code at the end of it:

thread.sleep(6000);
return true;

Now, this was done so the jQuery ajax call from the client gets delayed and the ajax animation will show for a little bit longer.

This is very wrong in my eyes. There shouldn't be this kind of connection between UI and server side. If he wants the animation to take longer he can use the setTimeOut function in the client side.

Here is my problem: how can I explain to the programmer why this is so wrong? Not just because the client/server thing, but why ever call thread.sleep on a website?

Answer 1

While delaying:

• You are using/blocking a thread
• You are consuming memory
• You have an open TCP/IP connection

these are all expensive resources on server

Because:

• If another requests comes in, the odds are greater a new thread must be created, so this will use CPU, memory etc, and this will delay this request. (Goto start of sentence).
• More memory consumption, means more page faults, larger disk queue. All requests take longer.
• TCP/IP connections are a limited resource.