Service Locator EJB Component - Clustering -oracle9iAS

[Viral Thakkar]

hi all,
Anyone has idea on how to implement the service locator (EJBHomeCache) component to make it cluster aware. I am using the oracle9iAS server.
thanks,
Viral

[Lasse Koskela]

What do you mean by cluster aware? If you get an EJBHome reference from the clustered JNDI tree, you shouldn't need anything else. I think. The EJBHome proxy itself should have the functionality to fallback to another server instance if the primary goes down etc.

[Pradeep bhatt]

Read this
http://download-west.oracle.com/docs/cd/A97688_10/generic.903/a97677/cluster.htm#1004903
You need to log into OTN.

[Lasse Koskela]

http://download-west.oracle.com/docs/cd/A97688_10/generic.903/a97677/cluster.htm#1004903

I can't get a response from the server. Are you sure this URL is still valid?

[Pradeep bhatt]

Yes, it is valid. I am able to access the site.
Try from http://otn.oracle.com/documentation/ias.html and then log into OTN.

[Lasse Koskela]

For some reason, the firewall blocked the requests. I found the docs using the laptop... Thanks.

[Viral Thakkar]

by cluster aware, i mean if i get a EJB Home reference from cache (using the Service Locator component) and the server having the object, is down so here i may get some exception.. so how i should make sure in my program so that i dont get this exception..
i referred to the EJB clustering link but here nothing is mentioned about EJB reference from the cache....

[Pradeep bhatt]

I guess that if you cache the ejbhome and servers in cluster are added or removed the stub will not be aware of it.

[Lasse Koskela]

by cluster aware, i mean if i get a EJB Home reference from cache (using the Service Locator component) and the server having the object, is down so here i may get some exception.. so how i should make sure in my program so that i dont get this exception.

Your service locator could hand out dynamic proxies, which intercept every call to the EJBHome, catch the first exception, retry after looking up a new reference from JNDI, and if it still throws an exception, rethrow it to the client.
Another possible approach has been presented in a JavaWorld article on Verified Service Locator
Pradeep, I think most containers don't have the functionality to inform existing stubs about new/dead servers but it wouldn't be that difficult to implement, I guess.

[Lasse Koskela]

Sorry for the duplicate post.
[ August 06, 2003: Message edited by: Lasse Koskela ]

[Pradeep bhatt]

Weblogic server provides smart stubs.
I doubt whether ServiceLocator pattern will be useful in Oracle 9ias.

[Lasse Koskela]

I doubt whether ServiceLocator pattern will be useful in Oracle 9ias.

Why? The performance implications of caching homes should be the same for Oracle than for BEA, IBM and others.

[Pradeep bhatt]

I rephrase it as - "It will not able to detetct new or removed servers, since it is cached".