Multithreaded Corba Client

Question

There is a lot on multithreading on the Corba server side, but I'm interested about the client side. We have a multithreaded client (Solaris, Orbix 6.3) with a Corba singleton "manager" that initialises the ORB. During runtime 'lsof' shows only one TCP connection to the Corba server, so all synchronous calls made from the client worker threads should be serialised.

Would like to change this arrangement to take advantage of parallelism: each thread to manage its own connection. I've changed the setup so that instead of a singleton each worker thread calls ORB_init(), etc.

Totally puzzled now: 'lsof' shows now 2 TCP connections but there are 6 worker threads. Something is not right, would have expected as many TCP connections as the number of worker threads. May be that the approach is naive - does it makes sense for example to call ORB_init() per thread?

I'd need someones opinion on this. Sample code for a multithreaded client would greatly help. Again, using Orbix 6.3 on Solaris.

Kind regards,

Adrian

Answer 1

The management of connections is implementation specific for plain CORBA. Each vendor has its own proprietary way of configuration their behavior. If you check the RTCORBA specification, that has a standardized way to configure how connections between client and server will be used.

I don't know how Orbix works and whether it supports RTCORBA, that is something you could get from their manuals probably. I do know that TAO has a lot of support for threading at the client side. By default when multiple threads make an invocation to the same server multiple tcpip transports can be opened at the same moment.

Answer 2

Thank you guys for your answers. I found, as Johnny says that this is indeed implementation specific.

omniORB has for example maxGIOPConnectionPerServer - default 5. That's: The maximum number of concurrent connections the ORB will open to a single server. If multiple threads on the client call the same server, the ORB opens additional connections to the server, up to the maximum specified by this parameter. If the maximum is reached, threads are blocked until a connection becomes free for them to use.

Unfortunately I haven't yet found out what's the equivalent (if any) for Orbix. It's definitely defaulting to 1 connection. Still googling...

Found out though that as part of Solaris -> Linux migration will be moving from Orbix to TAO in a number of months. Hoping TAO would be more friendly and customizable.