Abstract: A distributed computer system uses a single interface at the client site to handle calls to call both active and passive remote objects. Accordingly, the calling process does not need to be aware of distinctions between active and passive objects. Further, remote objects are aggregated into common groups of objects, thereby providing greater security between objects of disparate groups and efficiency between related objects of the same group. Preferably, different groups are run on different Java virtual machines.

Abstract: A stub retrieval and loading subsystem is disclosed for use in connection with a remote method invocation system. The stub retrieval and loading subsystem controls the retrieval and loading of a stub for a remote method, into an execution environment, to facilitate invocation of the remote method by a program executing in the execution environment. The stub retrieval subsystem includes a stub retriever for initiating a retrieval of the stub and stub loader for, when the stub is received by the stub retriever, loading the stub into the execution environment, thereby to make the stub available for use in remote invocation of the remote method. In one embodiment, the stub retrieval and loading subsystem effects the retrieval and loading for a program operating in one address space provided by one computer, of stub class instances to effect the remote invocation of methods which are provided by objects operating in another address space, which may be provided by the same computer or a different computer.

Abstract: A system for leasing a group membership in a distributed processing system is provided. In accordance with this system, a remote object requests from an activation group a membership in the activation group for a period of time. Responsive to this request, the activation group determines an appropriate lease period during which time the remote object becomes a member of the activation group and runs in the same address space as other objects of the activation group.

Abstract: In an object-oriented data processing system, methods and systems in accordance with the present invention provide a proxy class dynamically generated at runtime that implements a list of interfaces specified at runtime such that a method invocation through an interface on an instance of the class is encoded and dispatched uniformly to an object that performs the invocation of the requested method. The generation of the proxy class at runtime and the specification at runtime of the list of interfaces implemented by the proxy class allow the interfaces to be used to be chosen at runtime before generation of the proxy class. Since the proxy class does not need to be created before compile time, the interface list implemented by the proxy class does not need to be known at the time the source code is written.

Abstract: Methods and systems are provided that facilitate access to a service via a lookup service. A lookup service defines a network's directory of services and stores references to these services. A client desiring use of a service on the network accesses the lookup service, which returns the stub information that facilitates the user's access of the service. The client uses the stub information to access the service.

Abstract: A system for using a lease to detect a failure and to perform failure recovery is provided in using this system, a client requests a lease from a server to utilize a resource managed by the server for a period of time. Responsive to the request, the server grants the lease, and the client continually requests renewal of the lease. If the client fails to renew the lease, the server detects that an error has occurred to the client. Similarly, if the server fails to respond to a renew request, the client detects that an error has occurred to the server. As part of the lease establishment, the client and server exchange failure-recovery routines that each invokes if the other experiences a failure.

Abstract: A method and system for leasing storage locations in a distributed processing system is provided. Consistent with this method and system, a client requests access to storage locations for a period of time (lease period) from a server, such as the file system manager. Responsive to this request, the server invokes a lease period algorithm, which considers various factors to determine a lease period during which time the client may access the storage locations. After a lease is granted, the server sends an object to the client that advises the client of the lease period and that provides the client with behavior to modify the lease, like canceling the lease or renewing the lease. The server supports concurrent leases, exact leases, and leases for various types of access. After all leases to a storage location expire, the server reclaims the storage location.

Abstract: In accordance with the present invention a process is provided for allocating and deallocating resources in a distributed processing system having a requester platform and a server platform. The process involves receiving a request from the requester platform referring to a system resource and specifying a requested lease period, permitting shared access to the system resource for a lease period, sending a return call to the requester platform advising of the lease period, and deallocating the system resource when the lease period expires.

Abstract: A stub retrieval and loading subsystem is disclosed for use in connection with a remote method invocation system. The stub retrieval and loading subsystem controls the retrieval and loading of a stub for a remote method, into an execution environment, to facilitate invocation of the remote method by a program executing in the execution environment. The stub retrieval subsystem includes a stub retriever for initiating a retrieval of the stub and stub loader for, when the stub is received by the stub retriever, loading the stub into the execution environment, thereby to make the stub available for use in remote invocation of the remote method. In one embodiment, the stub retrieval and loading subsystem effects the retrieval and loading for a program operating in one address space provided by one computer, of stub class instances to effect the remote invocation of methods which are provided by objects operating in another address space, which may be provided by the same computer or a different computer.

Abstract: In accordance with the present invention a process is provided for allocating and deallocating resources in a distributed processing system having a requester platform and a server platform. The process involves receiving a request from the requestor platform referring to a system resource and specifying a requested lease period, permitting shared access to the system resource for a lease period, sending a return call to the requestor platform advising of the lease period, and deallocating the system resource when the lease period expires.

Abstract: An improved lookup service is provided that allows for the dynamic addition and deletion of services. This lookup service allows for the addition and deletion of services automatically, without user intervention. As a result, clients of the lookup service may continue using the lookup service and its associated services while the updates occur. Additionally, the lookup service provides a notification mechanism that can be used by clients to receive a notification when the lookup service is updated. By receiving such a notification, clients can avoid attempting to access a service that is no longer available and can make use of new services as soon as they are added to the lookup service.

Abstract: A method and system is provided to uniquely identify a remote method to invoke on a server using a hash value computed from the method signature sent from the client to the server with the call request. When a client wishes to invoke a remote method located on a server, the client sends a hash value identifying the remote method to the server in the “remote method invocation” (RMI) call. In one implementation, this hash value is created by applying a hash function to the method string name and the parameter type list and possibly the return type. When the server receives the RMI call, the server identifies which method is being called using the received hash value. The server maintains a mapping of hash values to their associated remote methods located on the server and references the correct method using the hash value. Additionally, in one implementation, the server creates the mapping table dynamically when a remote object is created.

Abstract: An improved lookup service is provided that allows for the dynamic addition and deletion of services. This lookup service allows for the addition and deletion of services automatically, without user intervention. As a result, clients of the lookup service may continue using the lookup service and its associated services while the updates occur. Additionally, the lookup service provides a notification mechanism that can be used by clients to receive a notification when the lookup service is updated. By receiving such a notification, clients can avoid attempting to access a service that is no longer available and can make use of new services as soon as they are added to the lookup service.

Abstract: Systems consistent with the present invention a method and apparatus is provided for selectively supplying a state change associated with remote objects in a distributed system. The method involves registering a request from a computational entity to receive notification as to a state change associated with a remote object. Registration of a notification request causes the creation of a remote weak reference to the remote object including an identifier of a location of the remote object. Periodically, a request is sent to a location based on the identifier of the remote weak reference. When it is determined that a state change associated with the remote object has occurred, the registered computational entity is notified accordingly.

Abstract: A system for leasing a group membership in a distributed processing system is provided. In accordance with this system, a remote object requests from an activation group a membership in the activation group for a period of time. Responsive to this request, the activation group determines an appropriate lease period during which time the remote object becomes a member of the activation group and runs in the same address space as other objects of the activation group.

Abstract: A system for leasing a group membership in a distributed processing system is provided. In accordance with this system, a remote object requests from an activation group a membership in the activation group for a period of time. Responsive to this request, the activation group determines an appropriate lease period during which time the remote object becomes a member of the activation group and runs in the same address space as other objects of the activation group.

Abstract: Downloading code for communicating with a device that joins a network. When the device joins the network, it transmits a multicast packet including a reference to code for use in communicating with the device. Receivers in the network use the reference to download the code for constructing objects to communicate with the device, and the receivers respond with a reference to a lookup service in the network. Using the reference from the receivers, the device registers with the lookup service.

Abstract: A stub retrieval and loading subsystem is disclosed for use in connection with a remote method invocation system. The stub retrieval and loading subsystem controls the retrieval and loading of a stub for a remote method, into an execution environment, to facilitate invocation of the remote method by a program executing in the execution environment. The stub retrieval subsystem includes a stub retriever for initiating a retrieval of the stub and stub loader for, when the stub is received by the stub retriever, loading the stub into the execution environment, thereby to make the stub available for use in remote invocation of the remote method. In one embodiment, the stub retrieval and loading subsystem effects the retrieval and loading for a program operating in one address space provided by one computer, of stub class instances to effect the remote invocation of methods which are provided by objects operating in another address space, which may be provided by the same computer or a different computer.

Abstract: A method and system for leasing storage locations in a distributed processing system is provided. Consistent with this method and system, a client requests access to storage locations for a period of time (lease period) from a server, such as the file system manager. Responsive to this request, the server invokes a lease period algorithm, which considers various factors to determine a lease period during which time the client may access the storage locations. After a lease is granted, the server sends an object to the client that advises the client of the lease period and that provides the client with behavior to modify the lease, like canceling the lease or renewing the lease. The server supports concurrent leases, exact leases, and leases for various types of access. After all leases to a storage location expire, the server reclaims the storage location.

Abstract: Use of a policy object for verification in a distributed system. A machine downloads a policy object containing a reference to code governing verification of data. The machine uses the reference to obtain the code and locally verify data or other information. As particular rules for the data change, the policy object may be updated to provide a reference to the code for the new rules when it is downloaded.