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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Tomcat Hangs with variable frequency
Date Wed, 22 Dec 2010 17:29:25 GMT
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Konstantin,

On 12/22/2010 11:56 AM, Konstantin Kolinko wrote:
> If closing the result set requires reading it in full (as JTDS does),
> it can take significant time.

Especially if the queries are something like

SELECT * FROM huge_table

> You should take thread dumps to see what the threads are doing and
> what they are waiting for. (Three thread dumps taken several seconds
> apart).

I would also inspect the queries that are in progress when these
connections appear to hang.

We had a problem with Oracle long ago where the table indexes had just
become horribly fragmented and performance slowed to a crawl. In an act
of desperation, someone ran "OPTIMIZE TABLE" on one of the tables
involved in particularly slow queries and basically everything got
better. From then on out, we called that "turning off the 'suck' bit" on
Oracle. :)

I would definitely like to see what queries are running on the server
and what their status is.

The problem is certainly /not/ Tomcat, here: threads are stuck in a
3rd-party library connecting to a 3rd-party database. Tomcat just
happens to be in the stack trace because that's the DBCP in use: the
driver appears to be hanging, not Tomcat's DBCP.

- -chris
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