[c3p0-users] C3P0 thread blocking GooGooStatementCache.acquireStatement

[Ruel L. <rue...@gm...>]

I'm hoping someone can point me in the right direction.

I'm performance testing my web application which uses hibernate and c3p0 v
0.9.1.1.

When the simulated userload is increased to 200 concurrent users I can see
using the YourKit profiler the majority of my threads in a blocked state.
The prepared statement setting is currently set to 1000.
The stack trace for these threads is as follows:

java.lang.Object.wait()
com.mchange.v2.c3p0.stmt.GooGooStatementCache.acquireStatement
com.mchange.v2.c3p0.stmt.GooGooStatementCache.checkoutStatement
com.mchange.v2.c3p0.impl.NewPooledConnection.checkoutStatement
com.mchange.v2.c3p0.impl.NewProxyConnection.prepareStatement
...

So i spent some time googling, grabbed the source code and looked through
it.

In  GooGooStatementCache.aquireStatement we create a new instance of
StmtAcquireTask and post it to the blockingTaskAsyncRunner.

 Runnable r = new StmtAcquireTask();
            blockingTaskAsyncRunner.postRunnable(r);

            while ( outHolder[0] == null && exceptionHolder[0] == null )
                this.wait(); //give up our lock while the Statement gets
prepared

What I am seeing is that this is waiting  5-10 seconds. before the wait is
released.   There is some type of starvation going on here....but I'm not
yet sure what.

Any ideas on what I should be looking for or any tips and tricks to debug
this?

Thanks!

R