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From Dan Wilga <dwi...@MtHolyoke.edu>
Subject ModPerl::Registry: Software caused connection abort
Date Fri, 30 Jul 2004 15:54:34 GMT
Configuration:

Red Hat Enterprise Linux AS release 3 (Taroon Update 2)
Kernel 2.4.21-15.0.2.ELsmp
mod_perl 1.99_14 (compiled from source; "make test" reports all tests 
successful)
OpenSSL 0.9.7a Feb 19 2003
Apache 2.0.50 (compiled from source)

./configure --prefix=/usr --localstatedir=/etc/httpd 
--sysconfdir=/etc/httpd/conf --sbindir=/usr/sbin 
--libexecdir=/etc/httpd/modules --enable-so --enable-auth-dbm=shared 
--enable-rewrite=shared --enable-mime-magic=shared 
--enable-ssl=shared --enable-mods-shared=most 
CPPFLAGS=-I/usr/kerberos/include

Problem:

Since switching from Apache 2.0.47 to 2.0.49, I have started 
receiving occasional messages in the error log of one of my SSL 
servers, like this:

[Fri Jul 02 11:14:30 2004] [info] Initial (No.1) HTTPS request 
received for child 0 (server [server name]:443)
[Fri Jul 02 11:14:30 2004] [info] (104)Connection reset by peer: 
core_output_filter: writing data to the network
[Fri Jul 02 11:14:30 2004] [error] 5894: ModPerl::Registry: Software 
caused connection abort at [path to script and line number].\n
[Fri Jul 02 11:14:30 2004] [error] 5894: ModPerl::Registry: Software 
caused connection abort at [path to script and line number].\n

This problem has persisted since I went to 2.0.50 recently.

What I've found so far:

- The script/line number recorded in the error log points to the 
library of perl functions we use to generate content dynamically. The 
script parses each HTML page and does special output. The error 
happens when the script tries to write the HTTP header to stdout. The 
script is configured to run, like so:

  <Files *.mperl>
    SetHandler perl-script
    PerlResponseHandler ModPerl::Registry
    PerlOptions +ParseHeaders
  </Files>
  AddType application/x-wrapper .shtml .shm
  Action application/x-wrapper [path to a .mperl script]

- Interestingly, this error only occurs on the SSL side of our server.

- I have a custom ErrorDocument for 500 errors which captures the 
environment variables of the session, and the user in all cases seems 
to be using IE 6.0.

- This error only happens about 10-20 times per day. I can reproduce it by:
    o  Navigating to a page on the site
    o  Clicking on a link from that page to another one on the site
    o  Quickly pressing IE's reload button, before the page from the 
previous step has a chance to display

   I have not received any complaints from users, so I suspect that 
the above case (or something similar to it) is the cause on the 
client's side.

- We upgraded from Apache 2.0.47, which did not exhibit this problem. 
Or, perhaps, the problem was there, but just wasn't getting reported 
like it is in .49 and .50.

- After reading up on the error messages, both using Google, and the 
Apache FAQ, I have tried these things, to no avail:

   SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown 
downgrade-1.0 force-response-1.0
   EnableSendfile Off
   EnableMMAP Off

I tried the latter two, because the web pages in question, while 
dynamically generating their output, are stored on an NFS-mounted 
partition. I figured it couldn't hurt, but it didn't help either.


I have written to the Apache Developers' list, but the only 
suggestion I got was that the initial "Connection reset by peer" 
error is to be expected, but that mod_perl probably shouldn't be 
generating the pair of "[error]" level log messages.

I don't entirely buy this, since there was a behavior change when 
only Apache was upgraded (I kept the same mod_perl version when this 
started happening.) It also only happens when SSL is added to the mix.

However, if you do agree that mod_perl needs to be more tolerant of 
this particular condition then, in my opinion, not only should the 
error not be logged with the "[error]" severity, but the 
ErrorDocument 500 should also not be called.
-- 
Dan Wilga                                         dwilga@mtholyoke.edu
Web Technology Specialist                     http://www.mtholyoke.edu
Mount Holyoke College                                Tel: 413-538-3027
South Hadley, MA  01075            "Who left the cake out in the rain?"

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