Re: Connecting Out of Process Servers via COM+


"Lance Wynn" <lance_wynn@xxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:eZobDukjFHA.3144@xxxxxxxxxxxxxxxxxxxxxxx
> This is what I was thinking of doing.
>
> Have you ever done anything like this before, and if so did it work well,
> did you get any difficult to track errors? I have never tried using a
> singleton server in this way, and so I am unaware of the many pitfalls
that
> could arise out of implementing it like this.
>
>

Yes, quite often. Every situation is different.

As you no doubt know - COM+ transcends just one language development
environment. Although VB has some unique builit-in properties to make it
easier to provide the working elements, COM+ itself is a different world,
its own quirks, its own rules, and don't take shortcuts.

The only real pitfall that might await you - is if you piss off your admin.
Then it can get ugly. Buy him beer, or her flowers, but get to know them,
keep them on your side.

<g>
-ralph

>
> "Schmidt" <sss@xxxxxxxxx> wrote in message
> news:OLKVp%23jjFHA.1148@xxxxxxxxxxxxxxxxxxxxxxx
>
> "Lance Wynn" <lance_wynn@xxxxxxxxxxxxxxxxxxxxxxx> schrieb im Newsbeitrag
> news:eW0UczijFHA.2152@xxxxxxxxxxxxxxxxxxxxxxx
>
> > Is there a setting where I can have COM+ instantiate only one instance
> > of the object (In this case, my connection wrapper) and allow client
> > applications to "share" this one instance of the COM+ object?
> I wouldn't try to find a setting for COM+ itself, to restrict the PoolSize
> of a specific COM+-object to 1.
> I would allow your clients, to access a "normal" configured COM+ Object
> (name it ComPlusRMIWrap).
> This ComPlusRMIWrap-Object (if requested) then accesses the
> RunningObjectsTable (ROT) on the serverside per GetObject(,
> "COMRMI.cServerDispatcher"), to get a (marshaled) Reference to your own
> ServerApplication (running as a sessionwide Singleton-Object on the
> COM+-Host).
> If you want to implement such a "Singleton-Server" in VB, you can use a
> Standard-Exe, that loads your RMI-DLL-Instance once, makes the connect to
> the Java-Environment and registers this Object in the ROT.
> Another (better, but more complicated) approach is, not to use a
> VB-Standard-Exe, but an ActiveX-Exe instead.
> With an ActiveX-Exe you can write a Server-Application, that can create
more
> than one instance of your RMI-Connection-Wrapper on different threads. If
> the AX-Exe starts, it would create a Dispatcher-Object first and registers
> that in the ROT (cServerDispatcher). This Dispatcher-Object is the
> Singleton-Object, that the COM+Objects can reference per GetObject. Inside
> the Dispatcher is a Thread-Pool-Collection (created at Startup) of (for
> example 10) RMIWrapper-Objects (cRMIWrapper). Those Wrappers are the
> (threaded) COM-Objects, wich create and hold a separate RMI-Connection
(from
> your Dll) inside.
>
> > If this is possible, how would I instantiate the teh object at the
client?
> > GetObject? CreateObject? When one client sent a command, it would
> > have to wait until the command had finished completely before
> > allowing the next client's command through.
>
> If two Clients at the same time are requesting the COM+-Server, the
requests
> are processed in parallel up to the point, where the Interface of the
> ROT-Singleton (the Proxy) is used. Interface-Calls of a marshaled
ROT-Object
> are queued automatically (the call, wich is a moment later will be blocked
> until the first request against the interface of the ROT-Singleton is
> finished).
> This means, altough COM+ would allow parallel requests, the calls would be
> serialized regarding the internal ROT-Object-Requests.
> In case of the VB-Standard-Exe, wich could place your RMIWrapper-Object
> directly in the ROT, your Clients would block each other during parallel
> RMI-Calls against the same ROT-Instance (I don't write a Code-Example for
> the COM+WrapperClasses - that case would be easy)
>
> In Case of the VB-AxtiveX-Exe, the ROT-Object is not the RMIWrapper
itself,
> it's a Dispatcher-Object, wich allows 'ThreadpoolCollection.Count'
parallel
> and async requests.
> Your COM+ Objects would then have some Code like this (Aircode, no
> error+timeout handling):
>
> Private RMIDispatcher as COMRMI.cServerDispatcher
>
> Public Function DoRMIRequest(Params)
> Set RMIDispatcher = GetObject(, "COMRMI.cServerDispatcher")
>
> 'The Dispatcher takes the Params, chooses a free RMI-Pool-Object
> internally
> 'and creates an EventObject, calls the PoolObject async and returns
> immediately
> hEvt = RMIDispatcher.GetFreePoolObjectAndCallAsyncWith(Params)
>
> 'The Dispatcher will raise a SystemWide-Event, if the threaded
RMI-Pool
> '-Object has finished the request and informed the ROT-Dispatcher
> WaitForSingleObject hEvt, TimeOut
> DoRMIRequest = RMIDispatcher.GetResult(hEvt)
> End Function
>
> Olaf
>
>
>


.

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