Plugging a leaky ship

Plumbr's Nikita Salnikov-Tarnovski writes Hunting down memory leaks: a case study. Quoting:

A week ago I was asked to fix a problematic webapp suffering from memory leaks. How hard can it be, I thought – considering that I have both seen and fixed hundreds of leaks over the past two years or so.

But this one proved to be a challenge. 12 hours later I had discovered no less than five leaks in the application and had managed to fix four of them. I figured it would be an experience worth sharing. For the impatient ones – all in all I found leaks from

• MySQL drivers launching background threads
• java.sql.DriverManager not unloaded on redeploys
• BoneCP loading resources from the wrong classloaders
• Datasource registered into a JNDI tree blocking unloading
• Connection pool using finalizers tied to Google’s implementation of reference queue running in a separate thread

Of course, there's more.