The Dangers of WordPress Multi-Site

A couple of months ago we started work on a multi site wordpress install. Everything was working smoothly. We pushed the codebase up to our staging site with no dramas.

Now a couple of months down the track a funny thing has happened. Multi site is no longer working. Suddenly we can no longer access the sub-domain. No one was sure exactly when it happened, and so it was hard to pinpoint exactly what had happened to cause it to break.

We store backups of all our databases, and as such had a working version of the database.

Now came the ardious task of tralling through data trying to find exactly what was causing the problem.

Process of Elimination 1

1. Replace each table in the good db with its corrosponding table from the corrupted db.
2. Test to see when multi site breaks.

Ok Sweet, its the wp-options table.

Process of Elimination 2

1. Replace each field of the good table with is corrosponding field in the corrupted table.
2. Test to see when multi site breaks.

Bingo!

active_plugins

But I looked through all the plugins and we use them on all our wordpress sites. Only, this isnt a normal wordpress site, its multi site.

And the culprit… Root Relative Urls

A WordPress plugin that converts all URL formats to root-relative URLs to enable seamless transitioning between staging/production host environments and debugging/testing from mobile devices, without the use of hackish tactics like textual find-replace strategies or risky hosts/NAT spoofing strategies.[1]

What to take away from this

1. WordPress multi site is very powerful, but must be used carfully.
2. If something goes wrong, your first step should be to disable all plugins, and then incrementally turn them back on to see if this is the cause of the problem.
3. Root Relative URL’s does not work out of the box for wordpress multisite.

References: 1. http://wordpress.org/extend/plugins/root-relative-urls/

Posted on August 30, 2012 at 3:31 pm.

Written by Kalki