Abstract: A signaling system of the present invention provides a synchronized approach to delivering, reporting, and/or otherwise processing status changes in a software dependency chain. In a first phase, the signaling system identifies all dependencies between software components, and further sets a binary indicator of each node in a first representation. After identifying any changes in a source node, the system (e.g., a value is updated), the system updates each binary indicator to a second setting. In a second phase, the system initiates all listeners in the dependency chain in an essentially progressive order from source node, to intermediate node, and end-node, etc. Once all listeners have had a chance to perform one or more processes based on the updated value, the system can discard the dependency graph, allowing a new dependency graph to be built for subsequent value changes.

Abstract: The setting up of a circular log implementation to be able to detect amnesia in a circular log, and to the determination of whether or not amnesia has occurred in such a circular log. Upon detecting a checkpoint trigger, information is preserved sufficient to detect whether or not the removed records ever existed in the circular log. If a request for information from a record were subsequently to be received by the circular log implementation, and if the record was not actually in the circular log, the preserved information could then be consulted to see if it indicates that the record had once existed in the circular log. If the information indicates that the record had once existed in the circular log, then amnesia has not occurred. If the information does not indicate that the record had once existed in the circular log, then amnesia has occurred. Accordingly, amnesia detection is made possible even in a complicated circular log implementation.

Abstract: Minimizing transaction managers. A method that may be practiced in a commit tree topology including a plurality of transaction managers to manage transactions. The transactions include a set of operations that are all performed if a transaction is completed or all aborted if a transaction is not completed. The transaction managers store transaction result information to allow recovery of a transaction in case of system failure. The method includes acts for minimizing storage overhead by minimizing the number of transaction managers used to coordinate transactions. The method includes identifying a set of transaction managers. A first transaction manager is selected from among the set of transaction managers. A second transaction manager is identified from among the set of transaction managers that is always available when the first transaction manager is available. Messages are redirected from a subordinate associated with the first transaction manager to the second transaction manager.

Abstract: Log file amnesia detection is accomplished by associating a unique identifier with each record in a log file, where each record receives a unique log sequence number. Multiple time intervals are associated with the log file with different events triggering the beginning of a new time interval. The log file implementation marks the beginnings of these multiple time intervals with a unique identifier. Every time an event occurs that triggers a new time interval a new unique identifier is generated. This unique identifier will be associated with the records in the log file that are created thereafter until the next unique identifier gets generated, marking the beginning of a next time interval. Log file amnesia can be identified when a log client requests information about a record and then comparing the unique identifier and log sequence number of the record with all records in the log file.

Abstract: A transaction manager virtualization layer is provided for supporting multiple active transaction managers in a cluster or node. By virtualizing the transaction managers, applications and services are enabled to migrate across cluster nodes or even outside a cluster that includes relevant recovery mechanisms for transactions that are not completed at the time of migration. Multiple implementations of a transaction manager may be enabled to run side-by-side in a node or cluster allowing a rolling upgrade of transaction managers in clusters.