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From "Marinko, Jeff" <>
Subject RE: Connection/acceptCount Problem
Date Fri, 09 Aug 2002 19:05:49 GMT
JDK:  1.4 and 1.3.1 (currently 1.4)

OS:  WinNT 4, no service packs on test machine

enableLookups: Maybe slight improvement.  I already stated it could handle
150 TPS with it set to "true".

test tool:  custom program.  I did not write it, only using it.  Not running
IIS, but I'm pretty sure it is not the tool.  Currently "testing" Tomcat
versus some custom C++ code (using the same tool for both), and the
connection problem does not happen with the C++ code.

Like I said before, I'm pretty sure it's Tomcat. Once the problem starts
happening, Tomcat's CPU usage nearly doubles when running relatively low TPS
values (like 40).

-----Original Message-----
From: Sexton, George []
Sent: Friday, August 09, 2002 11:50 AM
To: Tomcat Users List
Subject: RE: Connection/acceptCount Problem

You really aren't giving enough detail in your messages. You are trying to
treat a complex problem (hundreds of transactions per second) as a simple,
something is wrong with one thing issue. Scaling performance to these levels
is usually a combination of factors. There are rarely magic bullets when it
comes to things like this.

What JDK are you using? Have you tried using different JDKs?

What operating system are you using? You said WinNT in your initial post. Is
that WinNT 4? What service packs have been applied?

You never posted a response as to whether setting enableLookups="false" made
any difference.

What test tool are you using? Are you sure the issue is in Tomcat, and not
in the test tool/station? I assume you have IIS installed. Have you tried
using the same test tool to put 200 connections per second to IIS?

Have you tried scaling your transactions per second upwards and observing
the behavior at different loads?

George Sexton
MH Software, Inc.
Voice: 303 438 9585

-----Original Message-----
From: Marinko, Jeff []
Sent: 09 August, 2002 12:32 PM
Subject: Connection/acceptCount Problem

I've mentioned this before in my Configuration e-mail, but it appears
important enough for me to mention it again (as there hasn't been a
response, and it is a pretty serious problem IMO).

When I run tests at a high TPS, I might encounter a "can't connect" error
(looks like I've reached the acceptCount limit).  That's fine with me, so I
stop the test and get ready to start another.  When I start the next test (I
usually wait a few seconds, let tomcat's CPU usage drop off), I immediately
start getting "can't connect" errors, which should not be possible in the
amount of time I'm getting them (TPS of 100, acceptCount 1000, that should
be 10 seconds before I should get these errors, right?)

My only "fix" for this problem is to shutdown and restart Tomcat, which is
not really a solution.

Is this a known problem or bug? Possible I misconfigured something?


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