> 3: Regarding my inquiry about potential better options, I was more referring
> to the idea of maybe using Tomcat as a proxy to Tomcat backend  application.
> I've read it can be done was wondering if the like to like might provide
> advantages.  I am personally not as familiar with Tomcat as I am with HTTPD
> and therefore would prefer using HTTPD if there are no significant reasons
> to use Tomcat --> Tomcat.

IMO it is better to leave the application server to do what it is
supposed to do, handle dynamic content generation. While leaving
static content as well as balancing to httpd, which is what it does
best.

>
> 4:  The sticky sessions need makes sense.
>
> I have attempted to set up the sticky sessions configuration in HTTPD but
> unfortunately I must not have it set up properly.  It's probably best if I
> create a new thread for that issue and will do so.

Sticky sessions can be very tricky to setup correctly.

In mod_proxy_balancer docs it documents very well that you probably
need to set all these three elements correctly according to how tomcat
was setup:

stickysession (the most obvious)
scolonpathdelim
route - according to the value jvmroute the tomcats have setup.



>
> Thanks again for your guidance.
>
> HB
>
> On Fri, Feb 23, 2018 at 12:57 AM, Daniel Ferradal <dferra...@apache.org>
> wrote:
>>
>> Hello,
>>
>> I'll try to answer point by point the best I can.
>>
>> 1º You can only use one balancer method, so choose the best strategy
>> for your case. There is plenty on the description for each in the docs
>> (TL to explain here).
>> 2º No, it does not, you choose one and use only one that suites you
>> best for a specific balancer.
>> 3º Inside httpd the only non-third party choice that I know is
>> mod_proxy_balancer, so yes, by all means use it. Unless you find a
>> more suitable product for your needs.
>> 4º That will precisely mean you need to use sticky sessions and define
>> how to properly handle them at the balancer level, why? because as
>> long as nodes are up and running you  want to deliver the session to
>> the specific node dealing with that session or session will be lost.
>> It is when that backend node is down that httpd should look for other
>> nodes to deliver the session. Afaik is called session persistence. Or
>> at least this is the usual way to balance with sessions dealt by a
>> backend cluster.
>>
>> About docs you can also visit:
>> http://httpd.apache.org/docs/2.4/howto/reverse_proxy.html
>> and mod_proxy itself: http://httpd.apache.org/docs/2.4/mod/mod_proxy.html
>>
>> Cheers!
>>
>> 2018-02-23 1:48 GMT+01:00 Herb Burnswell <herbert.burnsw...@gmail.com>:
>> > All,
>> >
>> > I am looking for some guidance on using HTTPD as a proxy and load
>> > balancer
>> > to a backend Tomcat application.  Specifically, I'm interested in how to
>> > best handle the balancing of requests.  The configuration would be very
>> > much
>> > like the 'typical implementation' shown in this Reverse Proxy Guide:
>> > https://httpd.apache.org/docs/2.4/howto/reverse_proxy.html  (I'm using
>> > version 2.4.6):
>> >
>> > +---------------------  +
>> > |     Firewall Public |
>> > +---------------------  +
>> > +-------------------------------------------+
>> > |      +------+   +-------+  +-------+      |
>> > |      | httpd|   | httpd  |   | httpd |      |
>> > |      |    1   |   |   2      |   |   3     |      |
>> > |      +------+   +-------+  +-------+      |
>> > +-------------------------------------------+
>> > +----------------------  +
>> > |     Firewall Private |
>> > +----------------------  +
>> > +---------------------------------------------+
>> > |    +--------+  +---------+  +--------+      |
>> > |    | tomcat|  |tomcat |   |tomcat |       |
>> > |    |   1       |  |    2      |   |   3       |      |
>> > |    +--------+  +---------+  +--------+      |
>> > +---------------------------------------------+
>> >
>> >
>> > We have this working fine with a vanity URL to a VIP on our public
>> > firewall
>> > --> to the 3 httpd proxy load balancer pool --> to one of the 3 backend
>> > Tomcat server pool.  We want everything to run over SSL and the
>> > currently
>> > working config on the httpd servers is basic:
>> >
>> > <VirtualHost _default_:443>
>> >
>> >         ServerName example.com
>> >
>> >         SSLEngine on
>> >         SSLProtocol all -SSLv2 -SSLv3
>> >         SSLCipherSuite HIGH:MEDIUM:!aNULL:!MD5:!SEED:!IDEA
>> >
>> >         SSLCertificateFile /etc/pki/tls/certs/ssl.crt
>> >
>> > # ------------------------------------------------
>> > # Proxy Load Balancer
>> > # ------------------------------------------------
>> >
>> > <Proxy balancer://mycluster>
>> >
>> >         BalancerMember https://app1.example.com:9009
>> >         BalancerMember https://app2.example.com:9009
>> >
>> > </Proxy>
>> >
>> > SSLProxyEngine on
>> > SSLProxyVerify none
>> > SSLProxyCheckPeerCN off
>> > SSLProxyCheckPeerName off
>> > SSLProxyCheckPeerExpire off
>> >
>> > ProxyPass / balancer://mycluster/
>> > ProxyPassReverse / balancer://mycluster/
>> >
>> > </VirtualHost>
>> >
>> >
>> > As mentioned, this works fine.  But now we need to dig into the request
>> > management.  I read here:
>> > https://httpd.apache.org/docs/2.4/mod/mod_proxy_balancer.html that the
>> > scheduler algorithm is provided by 'at least one of':
>> >
>> > mod_lbmethod_byrequests
>> > mod_lbmethod_bytraffic
>> > mod_lbmethod_bybusyness
>> > mod_lbmethod_heartbeat
>> >
>> > Questions:
>> >
>> > 1. Am I correct in reading 'at least one of' that multiple of these
>> > algorithms can be used together?  If so, is there a hierarchy between
>> > them?
>> >
>> > 2. Does it make sense to use multiple algorithms?
>> >
>> > - It sounds like each could be desirable:
>> > mod_lbmethod_byrequests -> We do want to have an even distribution of
>> > request/sessions.
>> >
>> > mod_lbmethod_bytraffic -> Some requests/sessions could be more intensive
>> > than others.
>> >
>> > mod_lbmethod_bybusyness -> Sounds similar to byrequests?
>> >
>> > mod_lbmethod_heartbeat -> Definately need to backend to be listening but
>> > would be nice to distribute or overlook a server based upon response
>> > time.
>> > Is that part of how this works?
>> >
>> > 3. Is using HTTPD mod_proxy_balancer the best way to handle what we are
>> > looking to do?  Or are there better options?
>> >
>> > 4. On the backend we plan on using Tomcat session clustering for high
>> > availability.  That being the case, would that mean that we would NOT
>> > want
>> > to use sticky sessions at the HTTPD level in case a backend Tomcat node
>> > goes
>> > offline and the session is picked up on one of the other nodes?
>> >
>> > Sorry if I've confused anything here, any guidance is greatly
>> > appreciated.
>> > I'm happy to read any documentation directed to..
>> >
>> > Thanks in advance,
>> >
>> > HB
>> >
>>
>>
>>
>> --
>> Daniel Ferradal
>> HTTPD Docs. I translate to Spanish.
>> #httpd help at Freenode
>>
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>



-- 
Daniel Ferradal
HTTPD is the best!
#httpd help at Freenode

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