Abstract: In order to support filtering operations in a CORBA system, the marshaling and unmarshaling process is encapsulated in a server invocation object created from a class which contains data, including the request ID, the marshal buffer and the marshal and unmarshal methods. Filtering is supported by extending the class with a subclass that overrides the marshal and unmarshal methods to invoke the filters at the proper points. During operation, the CORBA object request broker examines the request to determine whether filtering is requested and instantiates a server invocation object either from the parent class, if filtering is not requested, or from the subclass, if filtering is requested.

Abstract: In order to support filtering operations in a CORBA system, the marshaling and unmarshaling process is encapsulated in a server invocation object created from a class which contains data, including the request ID, the marshal buffer and the marshal and unmarshal methods. Filtering is supported by extending the class with a subclass that overrides the marshal and unmarshal methods to invoke the filters at the proper points. During operation, the CORBA object request broker examines the request to determine whether filtering is requested and instantiates a server invocation object either from the parent class, if filtering is not requested, or from the subclass, if filtering is requested.

Abstract: A method is provided for load balancing requests for an application among a plurality of instances of the application operating on a plurality of servers. A policy is selected for choosing a preferred server from the plurality of servers according to a specified status or operational characteristic of the application instances, such as the least-loaded instance or the instance with the fastest response time. The policy is encapsulated within multiple levels of objects or modules that are distributed among the servers offering the application and a central server that receives requests for the application. A first type of object, a status object, gathers or retrieves application-specific information concerning the specified status or operational characteristic of an instance of the application. Status objects interact with instances of the load-balanced application and are configured to store their collected information for retrieval by individual server monitor objects.

Abstract: A method is provided for load balancing requests for a replicated service or application among a plurality of servers operating instances of the replicated service or application. A policy is selected for choosing a preferred server from the plurality of servers according to one or more specified status or operational characteristics of the servers, such as the least-loaded or closest server. The policy is encapsulated within multiple levels of objects or modules that are distributed among the servers offering the replicated service and a central server that receives requests for the service. Status objects gather or retrieve information concerning the specified status or operational characteristic(s) of each of the plurality of servers. An individual server monitor object operates for each instance of the replicated service to invoke one or more status objects and receive the necessary information. A central replicated monitor object receives the information from each individual server monitor object.

Abstract: Methods and devices for reducing computing overhead in a distributed client/server based computing system which utilize an efficient framework for marshaling and unmarshaling argument object references are disclosed. In one aspect of the invention, a method of unmarshaling an argument object reference, which includes a subcontract identifier, that is a part of an argument encapsulated within a marshal buffer involves identifying the subcontract identifier associated with the argument object reference, using the identified subcontract identifier to identify an appropriate associated unmarshal method, and calling the associated unmarshal method. In another aspect of the invention, a method of marshaling an argument object reference, which includes a subcontract identifier, that is a part of an argument encapsulated within a marshal buffer involves invoking a marshal method of a client representation in the argument object reference passing the marshal buffer as an argument to the marshal method.

Abstract: One or more filters may be included in each object implementation in a CORBA distributed object system. Each CORBA server object maintains a registry of filters containing unique identifiers and specifications for each of the filters and the order in which the filters must be applied. The filters execute selected code either before or after the conventional marshaling and unmarshaling which take place during a method invocation in the system. The CORBA client object builds a filter registry, from information that it received from the server. Filters may also be present in the client side of the ORB in order to execute code before and after the marshaling and unmarshaling that takes place in the client side of the ORB and these latter filters are also included in the client filter registry. The client then uses its filter registry to invoke the filters during a subsequent method invocation. The client also receives a time stamp from the server to identify the current filter composition.

Abstract: A trigger is provided in association with a network naming service, such as DNS (Domain Name Service), that handles client requests for an application. The trigger comprises a set of executable instructions referenced by a resource record associated with an identifier of the application. In response to a client request concerning the application, the resource record is retrieved and the instructions are executed. In one implementation of a trigger, a DNS server provides load balancing among a plurality of servers within a network name space (e.g., domain or sub-domain) offering an application program (or replicated service) that is known by a virtual server name. A policy is selected for choosing a preferred server from the plurality of servers according to a specified status or operational characteristic of the application instances, such as the least-loaded instance of the application or the instance with the fastest response time.

Abstract: Methods and devices for reducing computing overhead in a distributed client/server based computing system which utilize an efficient framework for marshaling and unmarshaling argument object references are disclosed. In one aspect of the invention, a method of unmarshaling an argument object reference, which includes a subcontract identifier, that is a part of an argument encapsulated within a marshal buffer involves identifying the subcontract identifier associated with the argument object reference, using the identified subcontract identifier to identify an appropriate associated unmarshal method, and calling the associated unmarshal method. In another aspect of the invention, a method of marshaling an argument object reference, which includes a subcontract identifier, that is a part of an argument encapsulated within a marshal buffer involves invoking a marshal method of a client representation in the argument object reference passing the marshal buffer as an argument to the marshal method.