AngularJS和MySQL实时通信

Question

I have built a web application using AngularJS (front-end) and PHP/MySQL (back-end).

I was wondering if there is a way to "watch" the MySQL database (without Node.js), so if one user adds some data to it, the changes are synced to other users too.

E.g. I know Firebase does that, but it's object oriented database and I am unable to do the advanced queries there like I do with SQL.

I was thinking to use $interval and $http and do ajax requests, so that way I could detect changes in the database. Well, that's possible, but it'll then do thousands of http requests to the server everyday and plus interpret php on each request.

I believe nothing is impossible, I just need an idea to do this, which I don't have, so that's why I am asking for a help here.

Answer 1

If you want a form of "real-time communication" you'll likely have to incorporate some form of long-polling from the client. Unless you use web sockets, but that's a big post about a bunch of different things. You're right to be concerned about bandwidth and demand on the DB though. So here's my suggestion:

If you don't have experience with web sockets then log your events in a separate table/view and use the pub/sub method to subscribe entities to an event, and broadcast that event to the table. Then long-poll against the watcher view to see when changes may have occurred. If one did occur then you query for the exact value.

Another option would be to use some query system with "deciders" that hold messages. Take a look at Amazon's SQS platform for a better explanation of how this could work. Basically you have a queue that holds messages and a decider chooses where to store the message using some hash or sorting method (to reduce run time). When the client requests an update, the decider finds any messages that would apply based on the hash/sort and returns them. Then you just have to decide how and when to destruct the messages.

The second option would require a lot more tinkering though, so it's really about your preference. I think what you'll find the difficulty to be is that most solutions have to deal with the fact that the message has to be delivered 1 or More times and you'll need to track when someone received the message and if it can now be deleted from the queue/event table or if you still need to wait. Otherwise you'll consume a lot of memory.