Javascript 1 second apart ajax requests? Resource usage?

I have a long-term goal of eventually creating a chat sort by any means, but for now I'd like to just have a simple one with some Mysql and ajax calls.

To make the chat seem instant, I'd like to have the ajax request interval as fast as possible. I get the feeling if it's as low or lower than a second, it's going to bog down the browser, the user's internet, or my server.

Assuming the server doesn't return anything, how much bandwidth and cpu/memory would the client use with constant, one second apart ajax calls?

edit: I'm still open to suggestions on how I can do a chat server. Anything that's possible with free hosting from x10 or 000webhost. I've been told of Henoku but I have no clue how to use it.

edit: Thanks for the long polling suggestion, but that uses开发者_C百科 too much cpu on the servers.

One technique that can be used is to use a long-running ajax request. The client asks if there's any chat data. The server receives the request. If there's chat data available, it returns that data immediately. If there is no chat data, it hangs onto the request for some period of time (perhaps two minutes) and if some chat data appears during that two minutes, the web request returns immediately with that data. If the full two minutes elapses and no chat data is received, then the ajax call returns with no data.

The client can then immediately issue another request to wait another two minutes for some data.

To make these "long" http requests work, you just need to make sure that your underlying ajax call has a timeout set for longer than the time you've set it for on the server.

On the server, you need to do an efficient mechanism of waiting for data, probably involving semaphores or something like that because you don't want to be polling internally in the server either.

Doing it this way, you can get near instantaneous response on the client, but only be making 30 requests an hour.

To be friendly to the battery of a laptop or mobile device, you need to be sensitive to when your app isn't actually being used (browser not displayed, not the current tab, etc...) and stop the requests during that time.

As to your other questions, repeated ajax calls (as long as they are spaced at least some small amount of time apart) don't really use much in the way of CPU or memory. They may use battery if they keep the computer from going into an idle mode.