What's my problem?
I'm encountering a problem with Tomcat 3 that I'm finding quite hard to describe and
search for succinctly. I'll outline it below, in the hope that someone on the list can
point me in the right direction. I'll assemble some more information and raise a bug
if that's the case.
I've got a web application running under 3.3a that is running under a fairly low load
of around five pages per second. (There's a mechanism which sits on top of this to
cache the output of the pages, so this load is irregular.) When Tomcat is receiving
these concurrent requests, the pages it serves are occasionally incorrect. The higher
the load I put it under -- up to ten concurrent requests at any one time for a
prolonged period -- the less accurate it's responses are.
For instance:
http://servername/contextname/servletname?argument=1
...will not always return me the same page. If the webapp is being loaded with
requests for argument=2, or argument=3, I might get one of those instead.
What have I done about it?
Very little so far, as it's taken me a while to isolate the problem to this level.
I've not been able to find any other report of this problem on the 'net, so I'll be
looking further into my application. I've tried turning most of the pooling and
caching off, and I'll ensure I get it all off. I'll try to provide a demonstrable
test-case, and I'll also look towards testing this on Tomcat 4, too, if no one tells
me I'm wildly off-course.
What do I think it could be?
I've replicated the problem with Apache 1.3.22 using the mod_jk that comes with 3.3a,
and also directly with Tomcat. I believe it could be:
* My worker configuration. (I can't imagine it's not thread-safe. I've not changed it
from the default.)
* My web application. (I think this is unlikely, but I would say that! :) )
* Tomcat 3.
I've seen this behaviour under Linux and Solaris 2.6 and 5.8. I've also seen it with
Tomcat 3.2.1.
Any pointers would be very appreciated!
Aidan Fitzpatrick
--
Aidan Fitzpatrick, Software Engineer, EU Tech Team
Tel: +44 (0) 207 903 6074 Fax: +44 (0) 207 903 6000 YIM: aidan_fitzpatrick
ZDNet, International House, 1 St. Katharine's Way, London, E1W 1UN
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