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From André Warnier>
Subject Re: [users@httpd] mod_proxy_ajp connections erratic
Date Thu, 23 Apr 2009 09:25:48 GMT
Craig Main wrote:
> On Thu, 2009-04-23 at 10:07 +0200, André Warnier wrote:
>> Craig Main wrote:
>>> Thanks Andre, 
>>> I am using apache to connect to 10 tomcat instances using the ajp
>>> connector with load balancing and sticky sessions.
>>> Apache: 
>>> Load [root@lt-webportal-01:~]  # /opt/apache/bin/apachectl -V
>>> Server version: Apache/2.2.9 (Unix)
>>> Server built:   Sep  6 2008 15:33:44
>>> Server's Module Magic Number: 20051115:15
>>> Server loaded:  APR 1.3.0, APR-Util 1.3.0
>>> Compiled using: APR 1.3.0, APR-Util 1.3.0
>>> Architecture:   64-bit
>>> Server MPM:     Prefork
>>>   threaded:     no
>>>     forked:     yes (variable process count)
>>> Server compiled with....
>>>  -D APACHE_MPM_DIR="server/mpm/prefork"
>>>  -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
>>>  -D HTTPD_ROOT="/opt/http-2.2.9"
>>>  -D SUEXEC_BIN="/opt/http-2.2.9/bin/suexec"
>>>  -D DEFAULT_PIDLOG="logs/"
>>>  -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
>>>  -D DEFAULT_LOCKFILE="logs/accept.lock"
>>>  -D DEFAULT_ERRORLOG="logs/error_log"
>>>  -D AP_TYPES_CONFIG_FILE="/opt/etc/httpd/mime.types"
>>>  -D SERVER_CONFIG_FILE="/opt/etc/httpd/httpd.conf"
>>> Tomcat: apache-tomcat-6.0.18
>>> Platform: CentOS 5.2 64bit
>>> The problem points to the ajp connection as we have done the following
>>> tests:
>>> 1) Load tested http with our static content. - Good Response times
>>> 2) Load tested with the tomcat ajp load balancing to 10 tomcat
>>> instances:
>>>         * When we test the site's static content, the speed is fine
>>>         * When we test the site's pages that go to tomcat, we see the
>>> same page returning sometimes fast, and other times slow.
>>>         * If we test connecting to the tomcat via it's http connector
>>> from the command line, the speed is fine under load.
>>>         * If we test connecting to the apache requesting the tomcat
>>> pages, some of the requests are returned quickly, others are slow.
>>> 3) At first we thought it could be an specific instance of Tomcat, but
>>> on investigation, one request to a particular instance was fast, and
>>> others we slow to the same instance.
>>> Please let me know if you need more information.
>> I believe that will do fine.
>> ;-)
>> Just another question, because someone is bound to ask : would it be an 
>> option for you to test with mod_jk instead of mod_proxy_ajp as a 
>> connector on the httpd side, and compare the results ?
>> Not to say that one or the other is better, but mod_jk has been there 
>> longer, and is probably more mature.  And it would help circumscribing 
>> the issue.
> This is what we are currently looking into. Will let you know when we
> have results on that.
If you have questions on mod_jk later on, it might be better to move 
this discussion to the Tomcat users list.  The developers of mod_jk 
generally follow this httpd list also, but tend to be more often on the 
Tomcat side, because officially mod_jk is under the Tomcat umbrella.
I suggest you then copy this whole message, since it has all the info.

One more question still : are you using any automated way to collect 
your performance info, or just visual impressions ?
It is always better to have some real numbers, and logfiles to compare, 
before changing the configuration.
There are a number of tools available for the purpose, but if you have 
perl installed on a system, I can give you a simple tool that would 
provide some scripted accesses and timestamped response times.

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