How Pingora keeps count

Pingora-limits is a Rust library for counting events efficiently using a probabilistic data structure called HyperLogLog++. It provides an estimator that can accurately count the occurrence of events with a small probability of overestimation, making it useful in scenarios where false positives are acceptable or can be mitigated by other means. The design is based on multiple hash tables and atomic counters to ensure lock-free and efficient performance. Pingora-limits is currently used in production at Pingora for the connection limit feature.