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From Costin Manolache <>
Subject Re: No sticky sessions (Re: Load Balancing)
Date Mon, 21 Aug 2000 22:04:12 GMT

There are 2 connectors - mod_jserv and mod_jk.

I know Gal did all the tests and worked with mod_jk, and
I remember he was able to do load balancing.

mod_jserv was imported from JServ, but I don't think
anyone fixed it for servlet 2.2 ( I remember the name
of the session cookie is different, and it may have
other issues).

Because mod_jk have a number of aditional features
that are not implemented in mod_jserv, and a structure
that make it very reusable I think it would be a good
idea to try to use it ( and fix it) instead of mod_jserv.

Mod_jk implements ( using almost the same code )
the ajp12 protocol from mod_jserv, but it also have
an ajp13 ( reuse the tcp connection between apache
and tomcat, much faster ), jni connector ( the
fastest - if you have a multithreaded server like
apache 2.0 ), support for apache 2.0 , support
for IIS, NES, AOL.

Please take a look. I never tried it with load balancing,
but the code is derived from mod_jserv ( and enhanced
a lot )


> wrote:
> > ugh. can we leave it the way it is ? its a really bad idea to
> > fiddle with
> > fairly complex C code and leave it untested/partially tested two weeks
> > before release...or at least have the option of removing the
> > sticky load balancing like JServ thingy...its does do sticky
> > stuff with
> > the same servlet...just not with more than 1 servlet.
> Why not fix it? Mod_jserv has been imported into Tomcat. The code to support
> it has been written. But it seems it's not just us:
> Joseph Chiu [] wrote:
> > Eep.  After digging around the source quite a bit more, I
> > partly retract the
> > part where I said "the mechanism that tacks on the jvmRoute
> > is missing".  I
> > see that there's code that sets the jvmRoute string to the
> > JServ "Route"
> > value...
> >
> > BUT, somehow, the session cookie still doesn't tack on the jvmRoute
> > string...  Sooooo, can anyone point me to how I can get the
> > JServ route
> > suffix in my session cookies, please?
> Clearly something just isn't quite right - but it's very close.
> As for whether or not an architecture with multiple web servers and multiple
> servlet machines is supported:
> mod_jserv's load_balancing is clearly designed with both multiple apache
> servers and multiple servlets (in this case JServs) in mind. Have a look at
> Bernard Bernstein and Jean-Luc Rochat's excellent paper:
> From what we've seen, we agree the code to support this model of operation
> seems to have been written into Tomcat, but unfortunately the ApJServRoute
> identifier isn't being appeneded to the JSESSIONID cookie by Tomcat, and so
> mod_jserv's load balancing and fault tolerence aren't working.
> Anything we can look for to track down exactly where it's failing?
>                 Andrew
> --
> Andrew Frederick Cowie
> Director of Operations
> Upoc, Inc
> cell: 917-217-4578  office: 212-405-1044
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