Split MySQL DB read/write for Drupal 5

kbahey wrote:
>There are patches to do master slave and reduce the load. We use them on drupal.org itself.

Yes, from those issues, it seems that at least the first patch (for database replication) -delayed a year ago from D6 to D7 development- was backported to D5, given that drupal.org ran and still runs on Drupal 5.

1. Yes. No patching needed. It will be in core using the new PDO.

2. Yes, but it has to wait till the D7 API is frozen and someone to put in the effort required.

Drupal performance tuning, development, customization and consulting: 2bits.com, Inc..
Personal blog: Baheyeldin.com.

There's quite a lot of interest in getting stronger database abstraction tools for Drupal 7, and I'm pretty sure that it will get in there if folks who want it (like you and me) stay active. Now is a good time to be filing issues and patches against the developing builds..

As for memcache, it'll almost certainly get a 7.0 port, as it's becoming a pretty popular piece of the high-performance stack.

http://www.chapterthree.com | http://www.outlandishjosh.com

To save other people from going through the same effort, please post a working patch against the latest Drupal core version (6.6. and 5.12, whichever you are using) to the same issue that you got the initial patch from.

Even if it will never go into core of stable versions, it will save others time.

Thanks in advance.

Drupal performance tuning, development, customization and consulting: 2bits.com, Inc..
Personal blog: Baheyeldin.com.

Are you asking if you point your Drupal build to a single MySQL server running in master-master mode, will it work? Most likely, yes, however there is no available code in Drupal (as of yet) that gives it the 'smart' reasoning to do fail-over to the other working database if more than one master server exists.

However, if you are wanting to double write (i.e. write to both db A and db B), I recommend reading this article first...

How to scale writes with master-master replication in MySQL
http://www.xaprb.com/blog/2008/08/06/how-to-scale-writes-with-master-mas...

Now, if you're looking at doing MySQL with split reads/writes, then you might consider the work I have done so far...

Given that Drupal does not have an option to do MySQL with a master/slave serving, I created my own patch code base for D5 using a combination of a number of older patch releases from a thread geared to D7.x (http://drupal.org/node/147160), but with references to how to do it under D5.x (http://drupal.org/node/147160#comment-561428) as well.

Using the D5.11 code as a base then applying Crell's patches through several trial and error recoding stages, I was able to come up with a MySQL master/slave combination + Drupal patch bundle (http://groups.drupal.org/node/16521#comment-56994). The new settings.php for the $db_url looks like this:

$db_url['default']['master'] = "http://user:password@example.com/master_database";
$db_url['default']['slave'] = "http://user:password@example2.com/slave_database";

So far via my testing, I do know that if you exclude using the 'slave' variable in the settings.php file and have it setup with two 'master' variables, it will only pick up the last 'master' variable entry and not combine the two.

$db_url['default']['master'] = "http://user:password@example.com/master_database";
$db_url['default']['master'] = "http://user:password@example2.com/master2_database"; <-- Only this is seen

I also know that if you try pointing the 'slave' to the other master MySQL server, only 'select' statements will be passed to the 'slave' rather than inserts/updates statements as the pager.inc and database.mysql.inc include files handle the db_query() functions.

-- Michael