what are the negative impacts of too many mysql (ajax) requests for a php chat application?

hi i created a simple php/mysql/Ajax chat application and I have a few questions. before that let me explain how it works.

So, if a user is on the chat page, the ajax script sends a request to a php file that shows the chat histories (latest messages), and returns it in HTML. This request is looped every second to show the latest messages to the user viewing the page.

so far its been working great.

now my question and concern is, 1.) What are the cons of using a method like this, if any? 2.) What things should i worry most about, if it开发者_如何学JAVA gets a large user base and many people are using it simultaneously? (mostly because its making a request every second, for each user on it..)

the mysql table is an innodb table, and I'm using only one SELECT statement without a WHERE clause.. something like SELECT * FROM table ORDER BY id DESC LIMIT 10 etc.. (basically, I'm making mysql do something very easy like cake)

3.) Any suggestion are welcome ;)

thanks very much

vikash

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Definitely, you will need to look at scalability issues for both the web server and database server. There are technologies such as MySQL clustering for improving performance on the database and web clustering for the HTTP side of things.

With large scale use you may also look at trimming down the table by removing early posts and dumping them to a separate table for low-frequency access. You could also have some method of caching the database requests via some worker threads so the database reads are minimal, but the front-end will have the ability to cope with the high volume of requests.

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I got 60 people in phpFreeChat (php/ajax/mysql chat) and it was a complete processor hog. It brought an 8 core server to its knees.