good work, lgtm Lari Hotari <lhot...@apache.org>于2025年6月24日 周二02:44写道：
> Dear Pulsar Community, > > I'd like to propose PIP-430, which addresses performance and > efficiency issues in Pulsar broker's entry cache eviction mechanisms > and introduces a more efficient caching strategy. > > The current broker entry cache implementation has several > production-impacting issues. The size-based eviction doesn't guarantee > removal of globally oldest entries, leading to suboptimal cache > utilization. More critically, the timestamp-based eviction iterates > through all ManagedLedgers every 10ms by default, causing high CPU > utilization in brokers with many topics. Mixed read patterns like > tailing, catch-up, and Key_Shared replays break eviction assumptions, > resulting in unnecessary BookKeeper and S3 reads that increase > operational costs. > > PIP-430 introduces two main improvements. > First, a centralized eviction mechanism using a global > RangeCacheRemovalQueue that tracks all cached entries in insertion > order. This replaces the expensive per-ledger iteration with a single > periodic task and ensures true oldest-first eviction globally. The > implementation PR for this part is > https://github.com/apache/pulsar/pull/24363. > Second, a new "expected read count" cache strategy where entries track > how many active cursors are anticipated to read them. This allows the > cache to intelligently retain entries that have higher utility, > especially in high fan-out catch-up read scenarios and Key_Shared > subscriptions. > > The benefits include reduced CPU overhead, improved cache hit rates > through better eviction decisions, and proper handling of diverse read > patterns. The new strategy is configurable via > cacheEvictionByExpectedReadCount (default: true) and maintains full > backward compatibility with no client-facing API changes. > > This addresses long-standing performance issues that particularly > affect production deployments with high topic counts or diverse > consumption patterns. The refactored architecture also provides a > solid foundation for future cache optimizations. > > The full proposal can be found at: > https://github.com/apache/pulsar/pull/24444 > Rendered PIP document: > https://github.com/lhotari/pulsar/blob/lh-pip-430/pip/pip-430.md > > I welcome your feedback and discussion on this proposal. Please share > your thoughts, concerns, or suggestions. > > -Lari >
