[Tclhttpd-users] TclHttpd-users digest, Vol 1 #534 - 1 msg

[Angel S. <xt...@am...>]

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>Today's Topics:
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>   1. Problem with form data in threaded tclhttpd (George Harvey)
>
>--__--__--
>
>Message: 1
>Date: Tue, 12 Oct 2004 21:01:04 +0100
>From: George Harvey <fr...@di...>
>To: tcl...@li...
>Subject: [Tclhttpd-users] Problem with form data in threaded tclhttpd
>
>Hi,
>
>I'm conducting some stress testing of an application, built on threaded
>tclhttpd, and I'm seeing some intermittent failures which appear to be
>related to the handling of form and cookie data returned to the server.
>I'm still trying to narrow down the problem but I'd like to describe the
>symptoms to see if anyone else has seen (or even fixed!) anything
>similar.
>
>The application is written in Tcl, loaded from the custom directory and
>accessed as an Application Direct URL. To test it, I have written a
>script (using tclwebtest) which will select all the menus, fill in
>forms, follow links etc. To stress test it, I run multiple copies of the
>test script on different machines.
>
>What I'm seeing is that a single test script runs OK but multiple copies
>will eventually fail. The failure occurs when a script does not get back
>the page it expects and can happen anytime from a few minutes to a
>couple of hours into the test. I'm using a session ID number, stored in
>a cookie, to keep track of session state and when a failure occurs the
>server log shows a mis-match between the session ID and the expected
>query data. What appears to be happening is that the query data for one
>session is somehow getting passed to a different session.
>
>The intermittent nature of the failures suggest that they are timing
>dependent, most likely needing a second request to arrive within some
>critical time window during processing of the first request. I've been
>looking at the tclhttpd code and can see that all the header and query
>data is held in a per-socket array in the master thread before being
>copied to the worker thread so it is difficult to see how it could get
>mixed up. I'm still trying to narrow this down.
>
>Anyone seen anything like this?
>
>For reference, I'm running Tcl 8.4.7, tclhttpd 3.5.1, tcllib 1.6.1 and
>thread 2.5.2. Tclhttpd is configured to run 5 threads and I have checked
>that worker threads are being created as expected. The server platform
>is Slackware 9.1.
>
>Regards,
>George
>
>
>
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1. What OS are you running the web server on?

2. If possible please take some small packet traces.

3. You may want to try and place some delays with in your code. Increase 
the delays untiil your custom code works correctly. This step is just a 
way of seeing how much of a delay needs to be introduced. The results 
can then be used for adjusting tclhttpd code if necessary.

4. Just make sure that as you test and introduce delays, you have been 
taking packet traces.

5. If it's ok with you, I can diagnose traces for you!!

Good Luck

    From: xt...@am...