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From Andy Wang <>
Subject Slow downloads through mod_jk on Windows XP
Date Mon, 07 May 2012 22:38:29 GMT
Hi all,
We've had a number of cases of people reporting to us that file 
downloads are slow when passed through tomcat and I've not been able to 
reproduce the problem on Linux but finally was provided a windows XP VM 
that was able to reproduce the problem.

This is Apache 2.2.22 and mod_jk 1.2.32 with tomcat 5.0.30 (yeah, I know 
this is ancient.  I'll try with something newer tomorrow).

I have two URLs configured both with an identical iso file (roughly 
450MB) in size.
When I go through the URL configured to run directly through Apache the 
download speeds on the file are around 30MB/s which is reasonable for 
what I would expect on the network connection between the client and the 
web server.

The second URL is JkMount'ed through to tomcat and download the same 
file drops down to 5-6 MB/s (starts at 10-ish MB/s).

The one thing I haven't tried configuring is upping the ajp packet size 
because the version of tomcat I was provided doesn't support that, but 
otherwise the operating system is tuned so the TcpWindowSize is 131072.

Unfortunately, this is windows, and both apache and tomcat are local on 
the server so I can't sniff the packets between the two systems with 

I don't see anything on the mod_jk configuration that 
deals with buffer sizes.

Hoping someone has some ideas on what to look at that might help tweak 
this thing to perform similarly to Apache direct downloads.


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