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From Matti Härö <matti.h...@infosto.fi>
Subject Re: Concurrency problem with Tomcat under Linux
Date Thu, 11 Apr 2002 13:59:44 GMT
Sorry, I forgot the page directive from the example. We solved the 
problem by removing the buffer="16000" attribute from the page directive 
and voila-everything seems to work fine!

Matti Härö


Matti Härö wrote:

> We are getting empty responce bodies from Tomcat under Linux under 
> stress testing. We managed to find out in what circumstances the empty 
> bodies are delivered by Tomcat, but we would like to know the cause.
>
> While running Tomcat version 4.0.3 under Linux, and trying to access a 
> single page simultaneously from two distinct browsers, we receive no 
> body in the responce, only responce headers. The responce header code 
> is 200. The error happens if the following conditions are met:
>
> 1) The server operating system is Linux (my kernel version is: Linux 
> pollux 2.4.9-13 #1 Tue Oct 30 20:11:04 EST 2001 i686 unknown)
>     The error does not appear under windows Tomcat versions.
> 2) The page is large enough, so that the previous request is still 
> executing while a new one is coming in. (need two separate browsers in 
> two separate machines for testing the concurrency problem)
>
> The error occurs with Sun's JDK 1.4, BlackDown's JDK, and IBM's JDK, 
> so the bug is propably not in the JDK implementation.
>
> When testing with older Tomcat versions, the problem also exists, but 
> the manifestation is a little bit different: There occurs a null 
> pointer exception in the servlet generated from the JSP page. The 
> NullPointerException occurs at the end of the servlet, on the line: 
> "out.flush();" This error also only occurs if there are two distinct 
> browsers accessing simultaneously the page.
>
> Here is an example page to demonstrate the problem:
>
> <%-- Page starts --%>
> <%@ java.util.*"%>
> <html>
> <head>
>  <title>My test page</title>
>  <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
>  <link rel="stylesheet" href="my_stylesheet.css">
> </head>
> <body bgcolor="#FFFFFF" leftmargin="10" marginwidth="10">
> <%
>   for (int i=0;i<=10000;i++) {
>    Date date = new java.util.Date();
> %>
>     <%= date %><br>
> <%
>   }
> %>
>  </body>
> </html>
> <%-- Page ends --%>
>
>
> Setting the LD_ASSUME_KERNEL=2.2.5 and reducing the OS stack size to 
> 2048 didn't have any effect on this behaviour.
>
> Has anyone come up with a solution to this problem?
>
> Matti Härö
>



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