Hi Brantley,
I've never really had a reason to examine this kind of data... so I'm no
expert on this... just guessing... as usual ;)
I think that error count is an indication of socket errors... which one
expects to have a few of.
There isnt really much we can do about socket errors.... other than make
sure the machine has enuf memory. To give you an idea of the type of socket
errors that can occur, on MS system anyway... have a look at this
http://msdn2.microsoft.com/en-us/library/ms740668.aspx
So for example when a machine gets really busy... the user gets fast enuf to
upset things a little... so for example a user can rudely close the
connection on the server, or impatiently ask for another connection... and
there is one already... so socket errors occur.
As u can see there are lots of other things that can happen... but the
things I would consider worthwhile looking at are things like... has the
machine got enuf memory, is there perhaps a proxy server or firewall that is
not coping... that sort of thing.
Also wot are u using to load test... you see a home written load tester that
rudely whacks away at the server will cause them... I like Jmeter... it
opens many connections... but each one is well behaved. The other thing I
have have seen is that people blame tomcat because they believe socket
errors are caused only by blocking sockets... ie the listening socket can
only serve one session at a time... tomcat would not be a multithreading
environment if that were the case... so I dont think thats the cause.
I like to think of it as normally a users reaction time is far slower than
the server... but that changes when a server gets busy... for example on the
web when you close a page because the thing is taking too long... the server
see's an interrupted connection... socket error.
The thing that doesnt seem right is ure session manager.... if you have not
touched the maxSessions setting... it should be unlimited... which is the
way I would leave it.... just check the machines memory under full load to
make sure its ok. So the only other thing I can think of is that you not
using sticky sessions correctly..... you need to make sure that when a
client comes in and hits a page with a session... that it then sticks to the
page... so other clients will toggle between servers, but once a session is
established... that client always goes back to the same server... unless you
doing something else fancy, like replicating sessions.
Without sticky sessions... or you will be getting new sessions and seeing
weird things like, forms not remembering the data etc etc.
good luck
----- Original Message -----
From: "Brantley Hobbs" <[EMAIL PROTECTED]>
To: "Tomcat Users List" <users@tomcat.apache.org>
Sent: Monday, May 14, 2007 10:25 PM
Subject: JK Connector "errors" under heavy load
All,
I'm doing some load testing and I'm having a bit of trouble trying to
interpret the numbers on the Tomcat Manager's "Server Status" page.
Specifically, each defined connector (http or jk) has a block telling you
the values of maxThreads, minSpareThreads, etc.
In my testing, I've found that I start getting some errors under heavy
load and the "Error count" number starts going way up on my JK connector.
Can someone tell me what "Error count" indicates?
Additional symptoms are that Tomcat appears to not have properly
associated a session with an incoming user (it doesn't get the wrong
session, it appears to get a new, empty session).
When I first started seeing this, I found that I was bumping up against
maxThreads, but now I have maxThreads sitting at approximately 125% of the
number of users I'm using to test, and I'm getting this same issue.
I'm unsure of where else to start looking for bottlenecks now. I'm not
CPU, I/O or database bound, but there's no other log entries.
For the record, it's Apache 2.0.52/mod_jk 1.2.22/Tomcat 5.5.23.
Thanks,
Brantley Hobbs
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