3.3.6 Global CORBA Naming Service

CTM-based request scheduling uses the global CORBA Naming Service as the naming service.

The global CORBA Naming Service is a naming service that manages information about the business-processing programs (stateless session beans) contained in the same CTM domain so that the information can be shared. The global CORBA Naming Service allows the hosts in the CTM domain to share the information about the EJB home object references registered on those hosts. The global CORBA Naming Service can be used to find J2EE servers on which a requested business-processing program is registered if that program is not registered on the J2EE server of the CTM daemon that received the request. With the global CORBA Naming Service, requests can be distributed to appropriate CTM daemons in this way.

A global CORBA Naming Service is deployed for each CTM daemon. CTM daemons exchange information with each other, including information about the business-processing programs on other hosts. Each CTM daemon registers this information in the global CORBA Naming Service on the local host. The information of the global CORBA Naming Services is thus shared within a CTM domain. Therefore, to obtain information about J2EE servers on other hosts, deploy a CTM daemon that runs only a global CORBA Naming Service (without running the J2EE server) on the integrated naming scheduler server.

The characteristics of a global CORBA Naming Service are as follows:

System availability can be improved by minimizing the area affected by a failure.

Information can be shared within a domain by deploying a global CORBA Naming Service for each CTM daemon. Therefore, if a problem occurs in the global CORBA Naming Service on a host, operation can continue with the global CORBA Naming Service on another host. As a result, system availability can be improved.
The lookup-target naming service does not need to be selected for each business-processing program.

If load balancing is implemented by clustering, the same information about business-processing programs (EJB home object reference information) is registered in all global CORBA Naming Services in the CTM domain. Therefore, the lookup-target naming service does not need to be selected for each business-processing program to be executed. This prevents the load from concentrating on a specific naming service, thus enabling proper load balancing.

The below figure is an example of processing in a system that uses global CORBA Naming Services.

In this example, the CTM daemons on hosts A and B are registered in the same CTM domain. Business-processing programs A and B are registered in the J2EE server on host A. Business-processing program C is registered in the J2EE server on host B. Note that a failure has occurred on host A. Also note that the EJB client application was started by specifying a system property (java.naming.factory.initial key) that is set to perform a round-robin search.

Figure 3‒13: Example of processing in a system that uses global CORBA Naming Services

The following describes the processing in the above figure:

For the EJB client application to start business-processing program C, first, an EJB home object reference to that program must be looked up from a global CORBA Naming Service. In this figure, the EJB client application executes lookup for the global CORBA Naming Service on host A, but an exception is thrown for the lookup because of a failure on host A.
If a global CORBA Naming Service fails when round-robin search is enabled with the EJB client application's system property, the application automatically switches the lookup destination to another global CORBA Naming Service in the CTM domain. In this example, the EJB client application re-executes lookup, and obtains an EJB home object reference to business-processing program C from the global CORBA Naming Service on host B. Business-processing program C, which is installed on application server B, can then be executed regardless of the failure on application server A.

If no failure occurs on application server A, the global CORBA Naming Service on host A returns a reference in response to lookup in step 1. When the EJB client application uses the reference to request create, the CTM daemons on hosts A and B determine which CTM daemon manages the request. As a result, an EJB home object reference to business-processing program C on host B is returned to the EJB client application.

Important note

If a problem occurs on a host on which a global CORBA Naming Service is registered, restart the application server on the host so that the CTM daemon re-registers schedule queue references in the global CORBA Naming Service.
While a request is being processed, CORBA::XXXX exceptions might be sent to the standard output or standard error output. These exceptions are harmless if processing continues without changing the status.

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