MySQL processes in Locked state - WordPress database

[Leirith]

Hi,

After upgrading WordPress to 3.1.1, I am occasionally experiencing 503 errors from Apache, and "Error establishing a database connection" messages. The database seems to be refusing connections.

I have noted that when the database is unavailable, there are a large number of MySQL processes in the "Locked" state. These processes are performing queries related to the WordPress database. What could cause so many processes to become "Locked" and how can I fix this?

Thanks!

[Rubberman]

It sounds like you are experiencing a deadlock situation with the database. Production database products, such as Oracle, will (usually) detect this and roll back all but one of the deadlocked applications, allowing one (random) one to complete. The others will have to restart their transactions. I'm not familiar enough with MySQL to say if it deals with this properly, but my guess is that there is some configuration options to help resolve this. FWIW, there have been a number of bugs in Oracle's dealing with such scenarios in the past, which caused similar deadlocks, and these have at times, regressed, with new releases... Caveat programmer! Sorry that I can't be more specific than this, but it may give you a lead as to where you should look.