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Vicky,

On 10/23/12 11:43 PM, vicky007aggar...@yahoo.co.in wrote:
> Andre & Christopher thanks a lot for your time & help.
> 
> One last query related to mod _jk & mod_proxy_balancer modules:- 
> among these two which one is preferred i mean which is more stable
> & has good performance.? Any idea
> 
> It will be great if you can share document link which talks about 
> there pros & cons

I have been using mod_jk for a very long time and I saw (at the time)
only one reason to make the switch to mod_proxy_ajp: it is bundled
with Apache and so you (likely) don't have to build the module yourself.

That said, simple configurations are *way* more simple in
mod_proxy_ajp than with mod_jk, although the (somewhat) recent
addition of JkWorkerProperty and JkMount "extensions" do help quite a bit.

mod_proxy_ajp can also be trivially swapped-out with mod_proxy_http
just by changing the URLs in your ProxyPass and ProxyPassReverse
directives to say http:// (or https://) instead of ajp://. This might
help you if you need to switch protocols for debugging purposes or if
you suddenly need switch to HTTPS to secure the traffic without any
external configuration (e.g. stunnel or VPN).

mod_proxy also supports ProxyPassMatch which lets you use regular
expressions in your URL mappings, which mod_jk's JkMount does not
(though you *can* use <LocationMatch> along with SetHandler in order
to achieve the same result, it's a cleaner configuration with mod_proxy).

That said, I have found that mod_jk supports more complicated
configurations where I have struggled to get mod_proxy_ajp to do the
same. Specifically, overlapping URL spaces that must be mapped to
separate workers. Technically speaking, I suppose you could use lots
of ProxyPassMatch directives and/or have a complex regular expression
to direct the various URLs, but again you end up with a rather messy
configuration that way. Messy configurations are a maintenance risk as
well as at risk of becoming "arcane knowledge" that nobody actually
understands and so they are afraid to modify it for any reason.

Generally, mod_jk will get fixed faster than mod_proxy_ajp due to its
independent release cycle: the httpd folks might have a fix for a
problem but it doesn't get released for a while due to testing of
other components, etc. At this point, mod_proxy_ajp has (IMHO) reached
a point of stability that this is less of an issue than it used to be.

At this stage, there is no reason for me to move any of my projects
from mod_jk to mod_proxy_ajp but if I were starting from scratch, I
might choose mod_proxy_ajp solely due to its binary availability and
simple configuration. If the configuration became complicated to the
extent that switching to mod_jk were a good option, then I'd move.

As for performance, I have no data on that one way or another. I would
suspect that mod_jk has a slight performance advantage because it has
been especially designed for the purpose rather than mod_proxy_ajp
which must support the mod_proxy API and might have a bit more
plumbing code to accomplish that. I would be surprised if you could
detect any performance difference between the two if you were to test
them both faithfully and with compatible configurations. If anyone has
relative performance data between mod_jk and mod_proxy_ajp, I'd be
happy to read it.

Hope that helps,
- -chris
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