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Date: Mon, 30 Aug 2010 08:29:38 -0300
From: Thiago Locatelli da Silva <thiago.silva@digitro.com.br>
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To: Tomcat Users List <users@tomcat.apache.org>
Subject: Re: Tomcat load balancing question x problem
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Thanks for your two cents Luca, they are a pretty smart idea on how to 
load balance thing in a expert way, however this is not a reality when 
you work for a company that a thinking line as "do more with less", they 
wont give me an extra nic for load balancing neither a third server... 
my constraint is: make servera do the balancing among servera itself and 
serverb. At a first sight I tought "what the heck?" since my small and 
insignifcant knowledge on architecture tell me that it stinks and its 
not a good practice, but since they pay for the food I eat and for the 
girls I hook up, lets do the way then want and in the future when they 
discover that it was not a good practice i will tell them: "i told ya"


*Thiago Locatelli da Silva*
/Analista de Sistemas/
/SIC - TDI - Tecnologia em Desenvolvimento de Interfaces/

*DÍGITRO TECNOLOGIA*
*E-mail:* thiago.silva@digitro.com.br <mailto:thiago.silva@digitro.com.br>
*Fone:* +55 48 3281-7000* Ramal:* 7726
*Fax:* +55 48 3281-7299
*Site:* www.digitro.com <http://www.digitro.com>

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Luca Gervasi escreveu:
> On Fri, 2010-08-27 at 09:17 -0300, Thiago Locatelli da Silva wrote:
>   
>> Hello list! :)
>>
>> Here at work I was asked to give a try on load balancing two tomcat 
>> servers running tomcat 6.0.29. The problem is that I was given only two 
>> servers to do this, what gave me only one option: run the apache in one 
>> of these servers. So I decided to put the apache httpd server which is 
>> going to balance the load among the two tomcat server in the Server A 
>> (suppousing I have server A and B running linux). My application which 
>> needs to be balanced has "/agent" context.
>>
>> Everytime I access the URL http://servera/agent my request is redirect 
>> either to http://servera:8080/agent or http://serverb:8080/agent. To my 
>> understanding, with load balancing, my url would remain 
>> http://servera/agent and the redirect would take place behing the scene 
>> and I would never see any redirect to tomcat connector port (8080). By 
>> the way, i am running the load balancing with mod_proxy in the apache 
>> server and my configuration is as follow:
>>
>> =============================================================
>>
>> ProxyPass /balancer-manager !
>> ProxyPass /status !
>> ProxyStatus On
>> ProxyRequests Off
>>
>> <Location /balancer-manager>
>>     SetHandler balancer-manager
>>     Order Deny,Allow
>>     Deny from all
>>     Allow from localhost   
>> </Location>
>>
>> <Location /status>
>>     SetHandler server-status
>>     Order Deny,Allow
>>     Deny from all
>>     Allow from all
>> </Location>
>>
>> <Proxy *>
>>     Order deny,allow
>>     Allow from all
>> </Proxy>
>>
>> <Proxy balancer://cluster>
>>     BalancerMember http://servera:8080/agent/ route=worker0 keepalive=On 
>> loadfactor=1
>>     BalancerMember http://serverb:8080/agent/ route=worker1 keepalive=On 
>> loadfactor=1
>>     ProxySet lbmethod=byrequests maxattempts=3 
>> stickysession=JSESSIONID|jsessionid
>> </Proxy>
>>
>> <Location /agent>
>>     ProxyPass balancer://cluster/ stickysession=JSESSIONID
>>     ProxyPassReverse balancer://cluster/
>> </Location>
>>
>> =============================================================
>>
>> Not happy with this scenario, i decided to install the apache httpd 
>> server in my laptop and made it as my load balancer instead of using 
>> servera to load balance. For my surprise, it worked out of the box with 
>> no extra configuration other than the one set up in my servera. I see no 
>> redirects to 8080 tomcat's port, due to my overall tests i could see 
>> only my desired url: http//localhost/agent (since i was running my tests 
>> with apache installed locally).
>>
>> So my question is: does it make sense to have the load balancer in the 
>> same server as one of the balanced server/application? Does mod_proxy 
>> support this?
>>
>> Many thanks for all the attention
>>
>> Thiago
>>
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>>
>>     
>
> Load balancing two tomcat with _two_ server is really... unusual :D
>
> I'd do this way:
> two httpd, one on each server, with a balanced ip (keepalived). Each
> httpd will use mod_jk and a balanced worker between the two istances.
>
> The server should have a second nic, to directly connect the two server
> with a different subnet.
>
> Consider that the two httpd are in an active/standby status. If one
> server goes down (i mean...it is off-duty), you'll end up with only one
> frontend working with one backend.
>
> If the "public" nic goes down, you'll end up with one frontend and two
> balanced backend.
>
> This is surely not an optimal solution, you know...
>
> If you have other frontend, you could use them to balance the two
> backends...mod_jk is not so consuming, after all.
>
> My 2 cents.
>
> Luca Gervasi
>
>
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>
>   

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