Abstract: A covert channel is established between a network service and one or more service monitors in a service group. The covert channel minimizes overhead by providing an indication of the status of the service through use of operating system utilities rather than conventional remote procedure calls (RPCs) or posting methods. The covert channel relies on one or more communication files established and updated by the service and having attributes which are in proportion to the workload of the service. By monitoring these attributes, the service monitor is able to determine the status of the service, including its workload and availability, without incurring costly operational overhead.

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: 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.