Re: mod proxy balancer problem/question...

[Sean Alderman <salderman1@xxxxxxxxxxx>]

I have proven, through my own experimentation, that removing the status=+H from the stateful balancer's member allow normal load balancing for the stateless proxy balancer.  Leaving the status=+H in the stateful balancer's config causes ALL requests in the stateless balancer to route to tccontainer1.  Reversing the balance member order under this scenario provides consistent behaviour, e.g. ALL requests goto tccontainer1, even though it's the 2nd balance member.  This implies to me that setting status=+H in the sticky balancer applies also to the stateless balancer, because tccontainer2 never receives any requests while the status=+H resides in the config.  If taken out of the config, the stateless balancer evenly routes requests to both tccontainer1 and 2.

The behaviour is odd and unexpected, but consistent.

FWIW, I used Apache Bench for the experimentation from multiple clients on the stateless side of things.  Unfortunately, due to the complexity of the stateful sessions I don't have a means to perform a test using apache bench, I can only do a manual test through an upstream application.

Thanks for your thoughts, your attention to my question is much appreciated! :)

On Tue, Apr 2, 2013 at 4:40 PM, Igor Cicimov <icicimov@xxxxxxxxx> wrote:

On 03/04/2013 7:28 AM, "Sean Alderman" <salderman1@xxxxxxxxxxx> wrote:
>
> Perhaps I've not explained correctly, I apologize.  The concept I was going for was to have two independent balancers that point to the same tomcat instances.
>
> In the webservices virtual host I would have a configuration like so:
>
>   ProxyPass /service-sticky/ balancer://webservices-sticky/service-sticky/
>   ProxyPassReverse /service-sticky/ balancer://webservice-sticky/service-sticky/
>
>   ProxyPass /service-stateless/ balancer://webservices/service-stateless/
>   ProxyPassReverse /service-stateless/ balancer://webservices/service-stateless/
>
> In my config, both of the quoted Proxy balancer directives exist and are referenced by a virtual host for different endpoints.  I absolutely understand what the status=+H does, and I was hoping to use it to confine all requests to services requiring stateful sessions to the tomcat instance on tccontainer2 unless it is offline.
>
> What I was trying to explain is that it would appear (by using mod status to inspect requests sent to each balance member) that applying status=+H to the balance member of one Proxy balancer, makes it apply to both, since the address:port of the balance members are identical between the two balancers.  I did not expect this behaviour and was looking for advice to accomplish the goal of load balancing the stateless requests across both containers and confining the stateful requests to one in a highly available way.
>
> Does that make more sense?
>

Not really, the proxy's have no dependencies of each other. Change the load factor in the second one from 1 to 2, thats the only reason i can think of that one not being used. Or try different lbmethod.

>
> On Tue, Apr 2, 2013 at 4:06 PM, Igor Cicimov <icicimov@xxxxxxxxx> wrote:
>>
>>
>> On 03/04/2013 2:02 AM, "Sean Alderman" <salderman1@xxxxxxxxxxx> wrote:
>> >
>> > Greetings,
>> >   I am running httpd 2.2.23.0-64 with mod_proxy to load balance Tomcat 6.0.36.B containers.  I have encountered a somewhat strange situation, and I was wondering if anyone could comment and or propose an alternative.
>> >
>> > I have a case where my tomcat containers have multiple webservice applications deployed.  Most of the deployments are stateless, but a few of them require session stickiness at the proxy layer.  I am looking for ways to better distribute the workload of the stateless webservice calls, with the hope of not having to create a new tomcat container separate stateful and stateless sessions.  The following configuration was tested, but had unexpected results...
>> >
>> > <Proxy balancer://webservices-sticky>
>> >     BalancerMember ajp://tccontainer2.test.udayton.edu:12002 route=webservices2-sticky
>> >     BalancerMember ajp://tccontainer1.test.udayton.edu:12002 route=webservices1-sticky status=+H
>> >     ProxySet lbmethod=byrequests
>> >     ProxySet stickysession=JSESSIONID
>> > </Proxy>
>> >
>> > <Proxy balancer://webservices>
>> >     BalancerMember ajp://tccontainer1.test.udayton.edu:12002 loadfactor=1 route=webservices1
>> >     BalancerMember ajp://tccontainer2.test.udayton.edu:12002 loadfactor=2 route=webservices2
>> >     ProxySet lbmethod=byrequests
>> > </Proxy>
>> >
>> > What I find is that balancer://webservices never sends any requests to ajp://tccontainer1.test.udayton.edu:12002.
>>
>> Thats because it never gets used, the requests are always being served by the first proxy. Why do you have 2 of them?
>>
>>  It would appear that the status=+H applies to the BalancerMember object instead of balancer://webservices-sticky.
>>  
>> Correct, it means that that balancer member is hot standby as explained in the documentation.
>
>