Clustering/Failover/ORB

Question

Hello,
I am trying to make a C++ client to connect to WLS6b2 on Win2000.
Although there is a lack of documentation, I hope I willbe able
to make the example in rmi_iiop work.
Beside that, I was wondering, and please tell me if I am wrong
or not, that with a C++ client using IIOP, we no longer have
load balance and failover if we have a cluster of WLS instances.
Let's me explain, the example shows a C++ client to use the IOR
of the WLS instance, which means I can only connect to this one.
I no longer have the Smart Stub approach in a C++ client case?!
Thank you.
Thierry

Answer 1

Hi,
My comments below.
"Eduardo Ceballos" <[email protected]> wrote in message
news:[email protected]...
Hey!
Thierry Janaudy wrote:
Hi Eduardo,
1. I successfully ran the examples in rmi_iiop yesterday.
Cool. Thank you. (C++, Inprise VisiBroker for C++, WLS6b2)Good. I expect more examples to follow after the GA date. Calling a CORBAserver from within WLS, an SSL example, to name two.
That is really nice. It does save a lot of time having these examples.
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2. About the clustering stuff, on the client side, the ORB as
you said does not manage anything.What if the IOR had the DNS name of the cluster instead of the IP addressof a single server? The DNS name resolution will round-robbin to another
cluster member every time DNS resolves the name, no?
Okay, it works.
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So your idea about a
special API giving back a set of IORs would be nice, but
you may have to provide more information. What happen
if I create a SFSB on a "Master server", WLS replicates
the content on a "Slave server". If my initial request to
the master fails, from your API, I should be able to know
the IOR of the Slave (which becomes the master), and therefore
be able to re-initiate a connection, and get the remote
reference to the "same" (conceptually) SFSB.
But... hmmm how do I do that?I think if you get the next IOR and narrow it to the SFSB interface youshould be ok.
But this IOR must represent the slave server where the information is
replicated.
Here is an example:
Let's have a cluster or 3 WLS instances, W1, W2, W3
My C++ client gets back an IOR for W1 and create a SFSB, which is replicated
on W2.
From your API, I know that W1 is the master and W2 is the slave.
W1 fails, I get a reference to W2 (Master now), and W3 is the slave. I am
able to
narrow and get the right SFSB.
But now, if I have an IOR with a DNS name, and if I am using DNS routing,
when W1 fails, I may go to W3, and then I have lost my SFSB.
So using DNS/IOR we have the load balance but not the failover.
The IOR API gives us a way to write smart CORBA stub, but we have
to write the code for failover and load balancing.
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Must I store the EJB Handle
(No because it is tied to one app server)..Handle would be alright, too, if it holds the DNS name of the cluster.Okay.
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Same problem with R/W entity beans (It does not matter for
SLSB and R/O EB)..With entity beans, you need at most once activation, which you will get inthe next release.
Which release are you talking about? WLS 6 FINAL?
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This API has to be defined in IDL. Or a Remote
Interface from which we can generate IDL anyway...
Yup, either way, you need an API for the C++ client to get a snap shot ofthe list of replicants.
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Here are some thoughts, I have to read the spec for the EJB
Handle.
3. I have found the newsgroup for RMI/IIOP. I have another
question. I would like to do a callback from a SFSB to a C++
CORBA client. Therefore I need and want to store this
reference as a private field of my SFSB... is there any doc
for this particular point?You mean you want the SFSB to call on a CORBA server object that is hostedin the C++ orb, yes? That works, but there's no example, yet. WHat you have
to do is define an RMI interface and RMI server class, generate the WLS RMI
stubs (using weblogic.rmic), and use COS Naming to bind the C++ server
object into the JNDI tree, where the WLS object can look it up. Of course,you don't need to bind servers into the JNDI tree to get this to work, I'm
just suggestion that you try to get this working before you attempt to
integrate the whole thread into EJB, etc.
Yes. I would like a C++ CORBA client to be able to create a SFSB, give it
areference
(in the create method) to a C++ callback object, store this reference as a
private
field of a SFSB. Therefore my SFSB would be able to make calls to this C++
callback object.
Best regards,
Thierry
http://www.mycgiserver.com/~janaudy/