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Subject DO NOT REPLY [Bug 50934] New: Intermittent empty HTTP response header in CGI request
Date Tue, 15 Mar 2011 15:44:35 GMT

           Summary: Intermittent empty HTTP response header in CGI request
           Product: Apache httpd-2
           Version: 2.2.17
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mod_cgi

Created an attachment (id=26773)
 --> (
Apache httpd startup script

When issuing HTTP CGI requests, the server sometimes returns an empty HTTP
response. This is an intermittent problem and seems to happen randomly.
I've reproduced it in at least 1 request in 100,000, using a very simple Perl
CGI script. With other scripts, I've had this issue happening a few (less than
times in 100,000 requests as well. The problem happens both when using HTTPS as
well as HTTP.

I've used an unmodified Apache 2.2.17 version, compiled with:

--enable-layout=Apache --enable-mods --enable-so --enable-vhost-alias
--enable-ssl --enable-expires --enable-rewrite --enable-proxy --enable-speling
--enable-deflate --enable-headers --disable-stat

The build platform is a Linux i686 and the list of shared libraries
is: => /lib/ (0x4001c000) => /usr/lib/ (0x4002b000) => /usr/lib/ (0x4006c000) => /lib/ (0x40140000) => /services/apache2217-original/lib/
(0x40163000) => /usr/lib/ (0x4017f000) => /usr/lib/ (0x4019f000) => /services/apache2217-original/lib/
(0x4027e000) => /lib/ (0x402a3000) => /lib/ (0x402b4000) => /lib/ (0x402e6000) => /lib/ (0x402fb000) => /lib/ (0x402fe000) => /usr/lib/ (0x4041e000)
    /lib/ => /lib/ (0x40000000)

The server has version 5.6.1 of Perl installed, though this may not be relevant
to the issue. The CGI script is attached to this bug report and is installed in
a directory named:

I setup a test to send 100,000 HTTP get request to the CGI script, using JMeter
(version 2.4) and have had an empty HTTP response at least once in 100,000
requests. This response is logged by JMeter about 20 seconds after the request
was initiated and doesn't appear to fork the CGI process. It appears that the
problem occurs before the script has a chance to run.

The GET request is


The parameters for this test are irrelevant and only mimic a request to a
different production script.

The attached CGI script logs each request with a timestamp in a temporary file
in /tmp.

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