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From rnilsen <rnil...@sfjbb.net>
Subject Re: Apache/mod_jk serves random files from tomcat
Date Tue, 17 Feb 2009 15:12:48 GMT

Hi,
We had similar behaviour on our server, apache in the front serving tomcat
on SSL, mostly servlets. First off, this is what we installed: Tomcat 5.5.27
and Apache 2.2.11 with mod_jk 1.2.26. The server is a 64 bit version of
Windows Server 2008 (2 CPUs). We got some strange problems with constant
high CPU usage. A thread suggested to change the tcnative.dll to an older
version since there was a bug in that, so we did and changed to version
1.1.6.0 (somewhere in the process we have misplaced the tomcat version this
file came with..) , and that got rid of the CPU usage problems.

But then another problem arose. After uploading documents into our system,
we could not download them successfully - this was first seen with PDF
files. And the larger the file, the more likely the problem. Then we noticed
that going directly towards Tomcat (on 8080) worked like a charm, so did
accessing static files under apache - but when trying the same static files
under tomcat - going through apache - it failed again. 

We have tried different versions of mod_jk with no success, and experimented
with mod_expires settings etc. Then we got reports of issues where large
servlet generated reports got messed up, and it seemed the stream had just
left out parts of the produced HTML code, only to continue further down in
the expected report. And finally, to top it, we also got data from one user
showing up at another user! 

After having no success we finally decided to try to remove the tcnative
DLL, and what do you know, it worked! No more problems with PDFs, and so
far, no more cut or mixed servlet response!

So what I want to know is, what could have caused this? My knowledge of both
Apache server and Tomcat is rather limited, so I hope someone can come up
with a good answer :)




Yuval Perlov wrote:
> 
> We started restarting apache on a regular basis but if a user is in  
> mid request (consider a user that just filled a big form and is  
> upload a file).
> 
> I moved all static content to apache so tomcat is now only delivering  
> the actual jsp file. The result was that the mix up took longer to  
> appear, however when it did USERS STARTED SEEING EACH OTHERS DATA!!!  
> (before that, the mixup was usually with images etc just because  
> there are more of them).
> 
> I am actually amazed that this can even happen in such a mature  
> version and that such a small number of us are experiencing it. This  
> is slowly killing our project. Trying to move to proxy_ajp did not  
> help which makes the whole thing even more mysterious - these are two  
> separate code bases, no? (BTW - are mod_jk developers reading this?)
> 
> We are contemplating two approaches:
> 1) moving to proxy_http. My only concern is that this won't help -  
> maybe the problem is unrelated to AJP? Upgrading has helped some  
> users but not all and the problem exists in both mod_jk and proxy_ajp.
> 2) getting rid of apache and moving tomcat to the front (much harder  
> to configure but ensures we are rid of this problem).
> 
> Any Thoughts?
> 
> Regards,
> Yuval Perlov
> 
> 
> 
> 
> On Feb 5, 2009, at 11:27 PM, LukeK wrote:
> 
> 
> 
> JohnHardin wrote:
>>
>> * Have others (that now seem to be "fixed") gotten things to work by
>> updating to the latest mod_jk (1.2.27)?
> 
> I suspect that it's related to 1.2.27 - I have been playing around with
> older versions. .24 and .25 have had issues forwarding certain request
> headers, but so far .26 seems to be working OK.
> 
> 
> Is periodically restarting apache a suitable (if not hackish) work- 
> around
> until we can get our production environment upgraded?
> 
> That'd be my fallback position.
> 
> Cheers!
> 
> Luke
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