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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: help analyzing thread dump for Tomcat 7.0.23 issue
Date Mon, 02 Jan 2012 23:09:13 GMT
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Mike,

On 12/29/11 9:01 PM, Mike Wertheim wrote:
> I did a stack dump on 7.0.23 when it was in its messed up state.
> No threads are blocked on critical sections of my app.

That's good.

> For the port 8080 connector, there are 196 threads in "waiting on 
> condition" and 4 threads in "runnable".

What were those 4 RUNNABLE threads doing?

> For the port 8443 connector, there are 81 threads in "waiting on 
> condition" and 119 threads in "runnable".

Well, that looks like it might be a problem. What about the stack
traces for THOSE threads?

When you say "slowly grinds to a halt" do you mean that there's point
where you can no longer accept HTTP requests? How about HTTPS? When
you get stuck, what does 'top' show? Do the threads look idle or are
you burning up your CPU?

> I don't know how to interpret this data, since I'm not really clear
> on what the difference is between "runnable" and "waiting on
> condition".

"Waiting on condition" means that the thread is asleep, waiting for a
notify() signal from another thread telling it to re-attempt a monitor
lock (i.e. enter a synchronized block). "Runnable" means that the
thread is actually doing something.

> Do these numbers seem normal, or are they perhaps giving a clue as
> to what the underlying problem might be?

If those are production numbers, then you don't look like you have 1%
HTTPS traffic -- at least not at the moment you took your thread
dump(s). Otherwise, your connector is getting fouled-up. There's
another thread this week about weirdness in the NIO connector that
sounds somewhat similar, but I doubt the causes are connected. You
might want to read that thread just the kicks.

- -chris
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