Publish/Subscribe Based Architecture of an Alert Server to Support Prioritized and Persistent Alerts

摘要

This report discusses various architectures and implementation issues and discusses our approach for a publish/subscribe based distributed alert server (SPAWAR application) whose requirements include: priority-based delivery, persistence, recovery, time-to-live and various other features. The approach described in this report provides a lightweight implementation that is general- purpose and can be used for a number of applications. A new efficient sweeping algorithm is used to make sure alerts are delivered correctly and satisfy several requirements such as priority, sending existing alerts to new subscribers, and regular expression based subscription. The approach was motivated by a need to provide alert distribution capability based on various needs, such as multiple ways to publish (using TAG, USER, and PROFILE), guaranteed delivery of alerts, asynchronous delivery and ack/receipt distribution. This approach is compared with various alternatives. The sweeping algorithm for priority-based delivery is described in detail.