[omniORB] Scalability and maxStrands

[Sai-Lai Lo]

rshoup@tumbleweed.com (Randy Shoup) writes:

>   We have run into a scalability problem using omniORB2.5.0, and wanted
> some input.  It seems that the maximum number of strands per rope is
> hard-coded to 5 in tcpSocketMTfactory.cc(529).  This means that a single
> client can only have 5 simultaneous connections to any particular
> server.  I have several questions:
> 
> 1. Is there any reason why this value is hard-coded to 5?

No particular reason for the value 5 other than that one would be hitting
the server really hard with more than 5 concurrent calls.

> 2. Would there be any problem increasing this value?

No problem other that you also have to be aware of the per process quota
imposed by the OS. Just change the value passed to the ctor of
tcpSocketOutgoingRope in

file:      tcpSocketMTfactory.cc: 
function:  tcpSocketMToutgoingFactory::findOrCreateOutgoing().


> 3. Are there any plans to make this more configurable -- e.g., through
> an ORB command-line argument or compile-time parameter?

Any hard-coded parameter is bad! I'll look into making this configurable.
Could be a ORB command-line argument. But on the other hand, we don't want
to clutter the ORB init function with zillions of options not particular
related to each other.

> In addition, comments in rope.h(759) imply that for maxStrands of n, the
> (n+1)'th request will block until a strand is released.  When we exceed
> the number of strands, instead of blocking, omniORB throws an
> exception.  This occurs both on NT4 and Solaris2.6.

This is a bug if it does so. I'll check. On the other hand, could it be
that you are hitting a limit on the server side? The server process may
have exceeded the maximum per process socket quota? Of course if your test
was done only between one client and one server we could discount this
possibility.

> 
> 4. Any chance this is fixed?

Of course.


Sai-Lai
-- 
Dr. Sai-Lai Lo                          |       Research Scientist
                                        |
E-mail:         S.Lo@orl.co.uk          |       Olivetti & Oracle Research Lab
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