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From Luca Toscano <toscano.l...@gmail.com>
Subject Re: [users@httpd] How does Apache detects a stopped Tomcat JVM?
Date Thu, 20 Jul 2017 21:19:54 GMT
Hello,

2017-07-18 15:48 GMT+02:00 Suvendu Sekhar Mondal <suv3ndu@gmail.com>:

> Hello Folks,
>
> I am new to Apache httpd world and wanted to know more about it. :)
>
> Reason I got interested in this is that, in our case, we are running
> multiple Tomcat JVMs under a single Apache cluster. If we shut down
> all the JVMs except one, sometime we get 503s. If we increase the
> retry interval to 180(from retry=10), problem goes away. That bring me
> to this question, how does Apache detects a stopped Tomcat JVM? If I
> have a cluster which contains multiple JVMs and some of them are down,
> how Apache finds that one out? Somewhere I read, Apache uses a real
> request to determine health of a back end JVM. In that case, will that
> request failed(with 5xx) if JVM is stopped? Why higher retry value is
> making the difference?
>
> If someone can explain a bit or point me to some doc, that would be
> awesome.
>
> We are using Apache 2.4.10, byrequests LB algorithm, sticky session,
> keepalive is on and ttl=300 for all balancer member.
>

https://httpd.apache.org/docs/2.4/mod/mod_proxy_hcheck.html is surely a
good read for your use case. Moreover be really careful with sticky
sessions, they have the downside to tie requests to a specific backend
altering the work of the LB algorithm.

Luca

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