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From Alan Chaney <a...@compulsivecreative.com>
Subject Re: Connection pooling again
Date Thu, 10 Apr 2008 13:44:24 GMT
Hmm. I think the answer here is one of resource starvation - the 
resource in this case being the CPU. It seems that  core of your test is

'Select * from table1'

Where is the database? Is it another application on the same box? What 
mechanism do you use to connect between the database and the app? (a 
pipe? tcp?) How big is 'table1'? How long does that select statement 
take? Why should anything else happen in the system until that select 
has finished?

Here's a guess. Look at a resource monitor and you will see that when 
you start your test the CPU goes to 100% and stays there.


I suspect that this is a case that you are queuing on processing the 
select statement in the database.

 From a systems point of view the Java JVM on windows and linux is a 
*cooperative* multithreaded system. Connection pooling has nothing to do 
with concurrency. Its as someone said earlier a performance optimization 
to avoid the overhead of recreating the datasource each time you need it.

It you want to write a test which shows the connection pool being used 
CONCURRENTLY then you must write a concurrent test! For example, open 
the connection, sleep for a while, do something, sleep again and do 
something else and then close the connection. Turn on logging for the 
pool and watch concurrent requests being processed.

Alan Chaney



daad@libero.it wrote:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Daad,
>>
>> daad@libero.it wrote:
>> | No, my test is done with threads that connect using sockets. Server
>> | listen with ServerSocket and 30 Threads are started connecting to it.
>>
>> Er... did you write your own server, or are you using Tomcat?
>>
> 
> I'm using tomcat.
> 
>> I'm sorry... all the evidence you have presented does not support your
>> conclusions. There are other ways to get a log file looking like the one
>> you posted.
>>
>> - -chris
>> -----BEGIN PGP SIGNATURE-----
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>> iEYEARECAAYFAkf9PnsACgkQ9CaO5/Lv0PBAPACfR8qL7tD33mFTWCdY99D6p8ic
>> shoAn3v0C49JvF2muOefUF5Q+QbBhVdD
>> =kLLa
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>>
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