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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 49713] New: Reverse proxy with MaxKeepAliveRequests=0 consumes memory without bound
Date Thu, 05 Aug 2010 22:17:59 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=49713

           Summary: Reverse proxy with MaxKeepAliveRequests=0 consumes
                    memory without bound
           Product: Apache httpd-2
           Version: 2.2.15
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mod_proxy
        AssignedTo: bugs@httpd.apache.org
        ReportedBy: adam@m154.homelinux.com


Created an attachment (id=25853)
 --> (https://issues.apache.org/bugzilla/attachment.cgi?id=25853)
Perl script that functions as a simple backend

Overview: Running Apache 2.2.16 on RHEL 5.5 as a reverse proxy.  When
KeepAlives is on, MaxKeepAliveRequests are 0 and MaxRequestsPerChild is 0, the
memory footprint of the httpd client processes grow without bound.

Steps to Reproduce:
1. Create a simple backend server that just kicks back a 200 OK for all
requests.

2. Change httpd.conf to have:
   KeepAlive On
   MaxKeepAliveRequests 0
   <IfModule prefork.c>
   StartServers       1
   MinSpareServers    1
   MaxSpareServers   1
   MaxClients       1
   MaxRequestsPerChild  0
   </IfModule>
   <IfModule mod_proxy.c>
   ProxyRequests Off

   <Proxy *>
      Order deny,allow
      Allow from all
   </Proxy>
   ProxyPass       /foo http://<ip of backend server>

Start up the server.

3. Flood the proxy server with requests.  I did this with 
   while :; do; wget -i urls.txt -q -O /dev/null; done

Where urls.txt was 1000000 lines of http://localhost/foo.  Run this loop on the
proxy server.

Actual Results: 
Top will show that the vsize and RSS for the 1 httpd process will grow without
bound until the machine runs out of memory.

Expected Results: 

I would expect the memory footprint to remain consistent.

Build Date & Platform: 

Apache 2.2.16 on RHEL 5.5.

Additional Builds and Platforms: 

Also seen on Apache 2.2.3 on RHEL 4.8.

Additional Information: 

A core dump of the httpd process during the run shows that the memory is being
taken up by the repetitive storage of the URI of the backend server over and
over.  After 15 minutes of running, I noted 700,000 strings equal to the ip
address and 2.1 million after 30 minutes.  I will attach the core dump
gathered.  For the backend server, I used the attached perl script to function
as a very simple server.

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