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From Peter Jones <...@roundroom.net>
Subject Re: [Was: OSGi and Jini] Now -> Next Steps
Date Wed, 15 Jul 2009 15:59:09 GMT
Just to be clear, the "com.sun.jini.jeri.tcp.useNIO=true" mode of the
JERI TCP endpoint implementation still uses multiple threads to
dispatch remote invocations-- RMI behavior would be drastically
impacted if it only used a single thread for that (for reasons like
you describe below).  It just uses a single thread for performing I/O
operations, at least those that "would block".

-- Peter


On Tue, Jul 14, 2009 at 4:12 PM, Gregg Wonderly<gregg@wonderly.org> wrote:
> The Jini 2.0 software includes the ability to use NIO in the TCP endpoint.
>  This is activated by system property "com.sun.jini.jeri.tcp.useNIO". If you
> look at TcpEndpoint and TcpServerEndpoint, you'll not find much different
> going on.  The biggest issue with a typical network "distributed" system, is
> circular wait that can occur as systems "randomly" develop new connections
> to other system.  Using a single thread to dispatch events in a server for
> "load handling" is not a good thing for any "work" that can have "external"
> contact.  So, the use of NIO for
> "scalability" is find for things that don't end up interacting circularly.
>  For things that you have no idea how they will interact, it's better to
> make sure that you have "new inbound call == new inbound thread" so that you
> don't get into problems.  It may be that there is some work that you can do
> in a single thread, but that usually is something that a specific
> application optimizes.
>
> One way to do that is to use inbound calls to "queue" work.  But then you
> need to use "callbacks" to notify the caller of the results of there
> request, unless you design a very custom invocation layer that allows the
> use of a "Future" or some other "signaling" mechanism to control when the
> result is sent back to the caller.
>
> Gregg Wonderly
>

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