Abstract: In general, the invention relates to a method for managing a two-node cluster. The method includes determining, by a first server node, that a second server node is disconnected from the two-node cluster when a first heartbeat response is not received from the second server node and sending a first echo request from the first server node to a first external system, where the first external system is specified on each server node of the two-node cluster. The method further includes receiving a first echo response for the first echo request from the first external system at the first server node and, in response to receiving the first echo response, providing, by the first server node, services of the two-node cluster independent of the second server node.

Abstract: In general, the invention relates to a method for managing a two-node cluster. The method includes determining, by a first server node, that a second server node is disconnected from the two-node cluster when a first heartbeat response is not received from the second server node and sending a first echo request from the first server node to a first external system, where the first external system is specified on each server node of the two-node cluster. The method further includes receiving a first echo response for the first echo request from the first external system at the first server node and, in response to receiving the first echo response, providing, by the first server node, services of the two-node cluster independent of the second server node.

Abstract: Improved techniques for managing operations of clustered computing system are disclosed. The improved techniques provide protection against potential problems encountered in operation of clustered computing. More particularly, the improved techniques can be implemented as an integral solution that provide protection against undesired partitions in space and partitions in time. The improved techniques do not require any human intervention.

Abstract: Improved techniques for controlled take over of services for clustered computing systems are disclosed. The improved techniques can be implemented to allow one sub-cluster of the clustered computing system to safely take over services of one or more other sub-clusters in the clustered computing system. Accordingly, if the clustered computing system is fragmented into two or more disjointed sub-clusters, one sub-cluster can safely take over services of the one or more other sub-clusters after the one or more other sub-clusters have been shutdown. As a result, the clustered computing system can continue to safely provide services even when the clustered computing system has been fragmented into two or more disjointed sub-clusters due to an operational failure.

Abstract: Improved techniques for dynamically altering configurations of clustered computing systems are disclosed. The improved techniques can be implemented to allow alteration of an existing configuration of a clustered computing system without having to completely shutdown the clustered computing system. As a result, the clustered computing system can provide uninterrupted services while the configuration of the clustered computing system is being dynamically altered, yet also safeguard against unwanted partitions in time or space.

Abstract: One embodiment of the present invention provides a system that facilitates recovering from failure in a distributed event notification system. During operation, the system detects a failure of an event forwarder, which notifies subscribers of events generated by distributed components in the distributed computing system. In response to detecting the failure, the system restarts the event forwarder, typically on another node in the distributed computing system. Next, the system requests a snapshot of current state from the distributed components. In response to this request, the system subsequently receives events from the distributed components that specify current state of the distributed components, and then forwards the events to subscribers that are registered to be notified of the events.

Abstract: One embodiment of the present invention provides a system that supports event notification within a distributed computing system. Upon receiving an event that was generated at a node in the distributed computing system, the system performs a lookup in a database to determine a list of clients that are registered to be notified of the event. The system then sends a notification of the event to clients in the list. In a variation on this embodiment, the event notification is performed by an event forwarding mechanism that is highly available. In this way, if the event forwarding mechanism fails, a new instance of the event forwarding mechanism is automatically started, possibly on a different node within the distributed computing system.

Abstract: One embodiment of the present invention provides a system that detects cycles in a set of dependencies between a set of resources in a computer system. The system operates by receiving a new dependency indicating that a first resource cannot proceed unless a second resource is able to proceed. The system determines if the new dependency creates a cycle in the set of dependencies by performing a search, which looks for cycles of dependencies starting from the first resource and ending at the first resource. If the search detects such a cycle, the system indicates that the new dependency creates the cycle. The system may also send an error message when the cycle is detected, and may abort further processing. In one embodiment of the present invention, the new dependency between the first resource and the second resource indicates that the second resource must be started before the first resource is started.

Abstract: Method for emulating persistent group reservations on non persistent group reservation-compliant devices, apparatus to perform the method, and computer-readable storage medium containing instructions to perform the method. The present invention enables the emulation of persistent group reservations on a non persistent group reservation-compliant device, including a shared disk, to enable the disk's implementation of persistent group reservation-reliant algorithms. This in turn enables the implementation of algorithms based on persistent group reservation features substantially without modification of those algorithms. One such algorithm is a quorum algorithm. One example of persistent group reservations is found in the SCSI-3 standard. The present invention accomplishes persistent group reservation emulation, or PGRE, by storing host- and reservation-specific information on a reserved portion of the disk and using this data to emulate the steps of certain persistent group reservation features.

Abstract: Improved techniques for controlled take over of services for clustered computing systems are disclosed. The improved techniques can be implemented to allow one sub-cluster of the clustered computing system to safely take over services of one or more other sub-clusters in the clustered computing system. Accordingly, if the clustered computing system is fragmented into two or more disjointed sub-clusters, one sub-cluster can safely take over services of the one or more other sub-clusters after the one or more other sub-clusters have been shutdown. As a result, the clustered computing system can continue to safely provide services even when the clustered computing system has been fragmented into two or more disjointed sub-clusters due to an operational failure.

Abstract: A method indexes a database so that records including literal values, and numeric values within a specified range can be located. The range is selected from an interval of values. Each record of the database is indexed by storing index entries in a memory. Each index entry includes a literal word entry representing a unique portion of information of the database, and one or more numeric location entries indicating occurrences of the portion of information. A plurality of sets of subintervals are generated from the numeric interval of values. Each set of subintervals includes all of the values of the interval. A first set includes one subinterval for each value of the interval, and each next set includes one interval for a group of adjacent subintervals of a previous set. The subinterval of the last set is the entire interval of numeric values. Each subinterval is represented by a unique literal which can be indexed as a word entry in the index.

Abstract: A method indexes a database so that records including literal values, and numeric values within a specified range can be located. The range is selected from an interval of values. Each record of the database is indexed by storing index entries in a memory. Each index entry includes a literal word entry representing a unique portion of information of the database, and one or more numeric location entries indicating occurrences of the portion of information. A plurality of sets of subintervals are generated from the numeric interval of values. Each set of subintervals includes all of the values of the interval. A first set includes one subinterval for each value of the interval, and each next set includes one interval for a group of adjacent subintervals of a previous set. The subinterval of the last set is the entire interval of numeric values. Each subinterval is represented by a unique literal which can be indexed as a word entry in the index.