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From Felix Schumacher <felix.schumac...@internetallee.de>
Subject Re: pure tomcat failover (no loadbalacing)
Date Sat, 30 Apr 2011 09:09:06 GMT
 On Fri, 29 Apr 2011 18:39:09 -0400, Christopher Schultz wrote:
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> Felix,
>
> On 4/28/2011 12:44 PM, Felix Schumacher wrote:
>> "Christopher Schultz" <chris@christopherschultz.net> schrieb:
>>
>> Felix and Guillaume,
>>
>>> I think you guys are working too hard for this. Isn't it as simple 
>>> as
>>> using a redirect from each worker to the other, with no clustering 
>>> or
>>> anything like that? You don't even need to set jvmRoute, etc. since
>>> there's no cluster.
>>
>> If you are willing to run all webapps on both servers, you are 
>> right.
>> But the original requirement was to have one set of webapps on one
>> server and one set on the other, with failover in case of downtime
>> of either one.
>
> Failover is not possible unless the target webapp is running on the 
> hot
> spare, so... ??!
 Right, the webapps are running on both servers at the same time, but 
 only
 one set of apps will be served the requests on each tomcat.

 The original req, as I understood it:

 tomcat1
   \-- /abc*  (active)
   |-- /def*  (passive)

 tomcat2
   \-- /abc*  (passive)
   |-- /def*  (active)

 If one of those tomcat servers shuts down, the other one should be used 
 as failover.

 The passive webapps should not be used in normal operations, because of 
 memory constraints.

 It was allowed to use them in case of emergency, to have some more time 
 to respond.

 Thus you will have to define a cluster - or rather two clusters -, if 
 you are using
 mod_jk, as failover and load-balancing are only possible within a 
 cluster.

 Two clusters are needed for each webapp group abc* and def*, since the 
 workers can not
 be in active and passive state at the same time.

 Do you think it could be made easier with mod_jk but use two clusters?

 It might be easier to set this up using mod_proxy_ajp, but I haven't 
 used it yet. But
 looking at the docs 
 http://httpd.apache.org/docs/2.2/mod/mod_proxy.html, it might look
 like this:

  # WARNING: I haven't tested this!
  ProxyPass / balancer://abc/
  <Proxy balancer://abc>
    BalancerMember ajp://localhost:9001 loadfactor=1
    # The below is the hot standby
    BalancerMember ajp://localhost:9002 status=+H
  </Proxy>
  ProxyPass / balancer://def/
  <Proxy balancer://def>
    BalancerMember ajp://localhost:9002 loadfactor=1
    # The below is the hot standby
    BalancerMember ajp://localhost:9001 status=+H
  </Proxy>

 Bye
  Felix

>
> - -chris
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