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I'm making a website which is going to have different chatrooms. Any user can create a chatroom at any time, and another user may join a chatroom when it is available. Max two users can chat in a single chatroom at the same time, but multiple chatrooms can exist.

I'm using AngularJS and PHP, with the PubNub API for the chat functionality. The created chatroom will be stored in a MySQL database, with the following fields:

  • User1: the user who created the chatroom. It may change or be null if it leaves.
  • User2: it will be null at first place and will store the user's name of the person who joins the chatroom.
  • Closed: when both users are offline, it will be true (1), then nobody can join anymore.

I have to update the columns "user1" or "user2" when any of the users leaves the chatroom. Then, check if both users are offline and then update the closed value.

I know that I can save the user's last connection by calling a PHP function via AJAX every 60 seconds, for example. Even I could check if the other user is still online by checking his last connection in the same function, but who is going to call the function to check if the last user left?

I wonder if I have to do that verification every time either any users request the available chatlists or I have to resolve it with another approach.

I guess that I can set a timeout function in PHP each time a user joins/creates a chatroom. That function is going to update the user column to null and update the closed value if both are null. When the user is in the chatroom, each 60 seconds another function will be called to postpone the first one. But I don't know if it is possible, and if it is possible using shared hosting.

I hope you can help me and thank you very much for your attention.

Craig Conover
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Alan Martin Revillagigedo Tula
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    Unless you're using websockets, the only signal you have is the time/date of the last request. Polling could help, but as you've found out that won't close the chat room. I don't see a good solution to this other than maybe a scheduled task to clean up rooms that have no active users. – Kevin B Jul 14 '16 at 15:52
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    Agree with Kevin about websockets... unless your server is written in php (not apache, but php itself listening at some ports) I suggest you use something like node.js for the chat messages on server-side. – SparK Jul 14 '16 at 15:57

1 Answers1

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PubNub Presence: Realtime vs Polling

The answer is - do not poll for presence, instead, have your server listen for changes in channel presence using PubNub Presence Web Hooks. Please read this article thoroughly as it details all the aspects of PubNub's Presence Web Hooks and then review the official documentation for PubNub Presence Web Hooks. The sample code for implementing the REST endpoint on your server to receive the web hooks is Node but you can use that code to implement that in PHP if required but if you can use Node for this purpose, it might be a better choice (and you could still use PHP for everything else).

I know your server has a chat room creation process that inserts new chat room record in your database so you don't need to know when the channel becomes active, but when user1 subscribes to the chat room channel, PubNub will send a channel active event via a web hook to your server, if you need to know when that happens.

When user2 subscribes to user1's chat room channel, PubNub will send a join event to your server via web hook and your server can use that event to update your database with user2's information.

Simultaneously, user1 and user2 will subscribe to the chat room channel and monitor presence (rather than poll with hereNow) and receive the join events, as well. When either user leaves the chat room (unsubscribes from the channel) PubNub will send a leave event via web hook to your server and directly to the user that is still subscribed.

Once the last user leaves the chat room, PubNub will send a channel inactive event to your server and your server can invoke its chat room closed process to update your database as required.

This is a fairly high level design and there are some other details to consider but the message here is do not poll PubNub for presence information. Only use hereNow to get the current state of presence of a channel and listen for further presence events from that point forward either via web hooks to your server or via presence/subscribe to your clients apps. In implementation, you actually subscribe with presence (listen for presence events) and then call hereNow.

For a more detailed discussion of your requirements as it pertains to PubNub, I would recommend contacting PubNub Support to put you in touch with a Customer Success Manager and Solution Architect.

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Craig Conover
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