PHP数据库值更改监听器，有没有更好的方法？

Question

Our company deals with sales. We receive orders and our PHP application allows our CSRs to process these orders.

There is a record in the database that is constantly changing depending on which order is currently being processed by a specific CSR - there is one of these fields for every CSR.

Currently, a completely separate page polls the database every second using an xmlhhtp request and receives the response. If the response is not blank (only when the value has changed on the database) it performs an action.

As you can imagine, this amounts to one databse query per second as well as a http request every second.

My question is, is there a better way to do this? Possibly a listener using sockets? Something that would ping my script when a change has been performed without forcing me to poll the database and/or send an http request.

Thanks in advance

Answer 1

First off, 1 query/second, and 1 request/second really isn't much. Especially since this number wont change as you get more CSRs or sales. If you were executing 1 query/order/second or something you might have to worry, but as it stands, if it works well I probably wouldn't change it. It may be worth running some metrics on the query to ensure that it runs quickly, selecting on an indexed column and the like. Most databases offer a way to check how a query is executing, like the EXPLAIN syntax in MySQL.

That said, there are a few options.

• Use database triggers to either perform the required updates when an edit is made, or to call an external script. Some reference materials for MySQL: http://dev.mysql.com/doc/refman/5.0/en/create-trigger.html
• Have whatever software the CSRs are using call a second script directly when making an update.
• Reduce polling frequency.

Answer 2

You could use an asynchronous architecture based on a message queue. When a CSR starts to handle an order, and the record in the database is changed, a message is added to the queue. Your script can either block on requests for the latest queue item or you could implement a queue that will automatically notify your script on the addition of messages.

Unless you have millions of these events happening simultaneously, this kind of setup will cause the action to be executed within milliseconds of the event occuring, and you won't be constantly making useless polling requests to your database.