Question

I have been asked to re-develop an old php web app which currently uses mysql_query functions to access a replicated database (4 slaves, 1 master).

Part of this redevelopment will move some of the database into a mysql-cluster. I usually use PDO to access databases these days and I am trying to find out whether or not PDO will play nicely with a cluster, but I can’t find much useful information on the web.

Does anyone have any experience with this? I have never worked with a cluster before …

Answer 1

I’ve done this a couple different ways with different levels of success. The short answer is that your PDO connections should work fine. The options, as I see them, are as follows:

If you are using replication, then either write a class that handles connections to various servers or use a proxy. The proxy may be a hardware or a software. MySQL Proxy (http://docs.oracle.com/cd/E17952_01/refman-5.5-en/mysql-proxy.html) is the software load balancer I used to use and for the most part it did the trick. It automatically routes traffic between your readers and writers, and handles failover like a champ. Every now and then we’d write a query that would throw it off and have to tweak things, but that was years ago. It may be in better shape now.

Another option is to use a standard load balancer and create two connections – one for the writer and the other for the readers. Your app can decide which connection to use based on the function it’s trying to perform.

Finally, you could consider using the max db cluster available from MySQL. In this setup, the MySQL servers are all readers AND writers. You only need one connection, but you’ll need a load balancer to route all of the traffic. Max db cluster can be tricky if the indexes become out of sync, so tread lightly if you go with this option.

Clarification: When I refer to connections what I mean is an address and port to connect to MySQL on – not to be confused with concurrent connections running on the same port.

Good luck!