存储聊天应用程序的“用户在线”列表（php / ajax）

Question

I have several chat rooms. Currently, I store the list of chat users in a php variable. If a user enters or leaves the room, the user's name is added/removed from that list. To make this storage persistent, I use memcached. To update the status of the chat room and send the user list to all users in the chat room, I use periodical ajax requests that fetch the user list into the browsers of the users who are in the chat.

It works okay. But I doubt that sending the whole list of chat users to everybody every XX seconds is a good idea if there are a couple of hundred people in the chat.

How are chat rooms usually dealing with this problem?

Answer 1

Have no idea how they do, but here are some ways you could. Remember to measure before and after you optimize.

• Version the list. Don't get the full list if you have an up to date version.
• Diff the list. Send only the updates since the last update.
• Log this list. Cache or push updates as new events occur.