Re: Using ServiceStarter to launch a "proxy is service" service

Gregg Wonderly wrote:
> Francisco Dário Mourão wrote:
>> Ok. That was my backup "tricky" solution... I didn't think it had to
>> be that way...
>> I thought ServiceStarter would have some special parameters to handle
>> it accordingly... Why isn't this code necessary for the remote case?
> 
> There are non-daemon threads blocked on "ServerSocket.accept()" (or NIO
> channels) that keep the VM from exiting.
> 


Gonna try and round that out some.....

Basically, when one instantiates a service consisting of back-end and
proxy there has to be some communications conduit between the two
components something like a socket or a SOAP connection or RMI or....

Many of these communications conduits are such that the server must
spawn additional threads to handle connections, ship data back and forth
etc.  The presence of these threads typically prevents the JVM from exiting.

On my pedantic days, I would say that this behaviour is a convenient
side-effect that a programmer shouldn't count on and thus the "tricky"
solution is actually the "correct" solution as well.

In the case of BasicJeriExporter there's a configuration option to
enable this "keepalive" behaviour but, of course you'd need a back-end
to make this option appropriate/useful.  In your specific example this
wouldn't be a sane option and there's no other entity in your design
which naturally would accept this responsibility and thus you have found
that it's assumed you'll code something suitable yourself!

Remember also the most common structure for a service is to have a proxy
and one or more back-ends and thus it might not be entirely surprising
to find certain things (like com.sun.jini.start) favour that model over
others such as the much rarer proxy only service.

We probably ought to post this up in a FAQ or a Wiki or whatever or
perhaps even put this in as an open issue for River to concern itself with.

Hope that's useful,

Dan.

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