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From André Warnier>
Subject Re: mod_jk not changes IP of hostname when occurs changing of IP on DNS
Date Sat, 21 Sep 2013 12:03:02 GMT
Tiago Braga wrote:
> Hi,
> I would like be automatic.

1) read this page carefully :
Particularly : "Important", item 6.

2) try to understand the answers which you have already been given.
Do not waste other people's time.

We understand that you would like this to be automatic, but the point is, it isn't 
automatic and it cannot be, for the reasons given before.

You can automate it yourself, using the scheme that Mladen indicated, but it has to be 
outside of httpd itself.  Create a watchdog program, which detects when the IP changes, 
and have it trigger a httpd graceful restart.
Or, much better, find another infrastructure where the IP address of the Tomcat servers 
does not change.


Ok, one more try to explain :
The only way to make this "automatic" within mod_jk, would be to have mod_jk do a DNS 
lookup *at every request* to verify if the IP address of the worker Tomcat has changed.
That would cause an enormous performance hit, which would probably make your application 
(and any other application) unworkable.
(And also, the people running that DNS server would probably complain)

In other words, the infrastructure which you have chosen (or which you are forced to use)

does not match well with the configuration that you are trying to use.

You can persist trying to eat soup using a fork, but it is likely to be frustrating in the


> Thanks.
> On Fri, Sep 20, 2013 at 12:29 PM, Mladen Turk <> wrote:
>> On 09/19/2013 06:41 PM, Tiago Braga wrote:
>>> In apache, the module mod_jk not changes IP of hostname when occurs
>>> changing of IP on DNS.
>> Do a graceful restart of httpd when address changes.
>> Unfortunately like some said, we can either do a DNS lookup
>> every time which would be a performance disaster or cache
>> it and reuse (like we do).
>> So graceful restart will cache a new DNS address.
>> Anyhow, I'd suggest you use fixed IP addresses for your backend
>> servers anyhow.
>> Regards
>> --
>> ^TM
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