Optimize distributed web/ejb expiration schedulers -------------------------------------------------- Key: WFLY-12581 URL: https://issues.jboss.org/browse/WFLY-12581 Project: WildFly Issue Type: Enhancement Components: Clustering Affects Versions: 18.0.0.Beta1 Reporter: Paul Ferraro Assignee: Paul Ferraro Priority: Major Attachments: Schedulers for distributed workloads.png, Schedulers for local workloads.png WF18 added a new expiration scheduler implementation for SFSBs specifically optimized for non-distributed environments. The key features of this implementations are: * Uses a single scheduled task instead of a scheduled task per SFSB * Uses a double-linked list to track SFSBs to be expired The use of a linked queue is based on the following assumptions: # All SFSB using a given scheduler share the same @StatefulTimeout # A given call to Scheduler.schedule(...) is always the last item to be scheduled Distributed SFSBs cannot use the same implementation because the second assumption is not valid, as a member may assume the responsibility of expiring a SFSB previously owned by another member. They can, however, leverage the strategy of using a single scheduled task instead of a task per SFSB. Due to the nature of the scheduler, that most scheduled tasks will be cancelled/removed and rescheduled, this strategy outperforms the current implementation. This jira proposes the following: * Generalize the Scheduler interface for reuse between SFSBs and web sessions. * Generalize the new local scheduler implementation such that the same scheduler can support both local and distributed SFSBs using different queue implementations for tracking scheduled items * Distributed use case uses a PriorityBlockingQueue, which has O(log N) add/remove characteristics * Replace ExpirationTracker with a ConcurrentDirectDeque to support local case, which has O(1) add/remove characteristics ** ConcurrentDirectDeque outperforms ExpirationTracker under concurrent load Local web session expiration cannot use the same expiration scheduler used by local SFSBs because the first assumption is not valid, since a given web session can override the default max inactive interval. However, we can still optimize the local web session case by delegating expiration to the PriorityBlockingQueue-based implementation if the session uses a non-default max inactive interval, and to the ConcurrentDirectDeque-based implementation if the session uses the default max inactive interval.