PHP: Most Efficient Way to Track if a User is Online?
php, scalable, tracking
Solution
Generally speaking it's a common practice to add a column to the users table to store the `lastActivity` time. Anytime the user logs in, or accesses a page, store the current time in that field. If you want to know whether or not they are online, see if the last recorded time is within a certain window - say, five minutes. You can query all rows to see how many users are currently online as a result.
I wouldn't be too worried about running queries every few seconds - your server can handle it (assuming these are well-written and not very verbose).
Problem
I'm developing a project of mine with scalability in mind and I've come to a crossroad. On my website I would like to detect if a user is online or not. And I can't quite think of the best way to handle this. The way I was thinking would be something along these lines(in psuedocode): ``` // SQL user table: user { "name": "blah blah", "email": "derpy@derpyderp.com", "online": false } ``` So whenever the user logs in I could update his `online` column to `true`. However that would eventually lead to SQL queries happening every time a user logs in and if it happens that I get say, 10 logins per second, well, that's a lot of queries happening. Another way I figured I could do the same thing but in a different table: ``` // Activity table: activity { "user_id": 2, "online": true } ``` For some reason I believe that would lead to less memory consumption because of the separation from the `user` table. However I'm not sure if it would have any actual effect on performance. So if you could bless me with your insight I would be more then grateful, thank you.