[Ace-users] [tao-users] Question about TAO IORTable - Extra Hop?

[Steve Totten]

Hi David,

Douglas C. Schmidt wrote:

>> SYNOPSIS:
>> Question about IOR Table - Extra Hop?
>>
>> DESCRIPTION:
>> Hi, I confused and hoping that someone could clarify something for me regarding with the IORTable.
>>
>> I've a server application that binds an IOR with a key to the IORTable.
>>
>> When a client creates a corbaloc using the same key that server binds to the IOR table and talks to the server, it appears
>> to me (based on the TAO debug I'm reading) that it seems like the server's IORTable responded back with the object
>> reference via Forward Request (guessing) and then the client's ORB re-invoke the invocation to the server.
>>
>> Is that the expected behavior?
> 
> Yes, that's the expected behavior.  
> 
>> If so, how come it designed such way because it seems like there's an
>> extra hop because the CORBA servant already resides on the server so
>> it should go directory to the servant instead of issuing a forward
>> request to the client and client's ORB then re-invoke it?

The IORTable can be used to forward a client to any location,
not just to a servant within the same server.  For example, one
could create a very simple forwarding server using the IORTable,
presenting a flat name space to clients for access to various
objects through simple corbaloc Object URLS.

Also, the "extra hop" you observed only happens on the initial
request on the target object.  Once the location forwarding
has occurred, subsequent requests to the same target object
do not need to go through the IORTable mechanism again.

> Please see Chapter 12 of the book "CORBA Explained Simply"
> <http://www.ciaranmchale.com/download/corba-explained-simply.pdf> for
> details on how corbaloc is specified by the CORBA standard.

There is a chapter about the IORTable in OCI's TAO Developer's
Guide, available for purchase via:

http://www.theaceorb.com/purchase/index.html

Steve
-- 
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  Steve Totten, Principal Software Engineer and Partner
  Object Computing, Inc. (OCI), St. Louis, MO, USA
  http://www.ociweb.com/  http://www.theaceorb.com/
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