I should also note that the probability of false positives does not fall below shape.P because as it approaches shape.P a new layer is created and filters are added to that. So no layer in the LayeredBloomFilter exceeds shape.P thus the entire filter does not exceed shape.P.
Claude On Tue, Apr 9, 2024 at 2:26 PM Claude Warren <cla...@apache.org> wrote: > The overall design for KIP-936 seems sound to me. I would make the > following changes: > > Replace the "TimedBloomFilter" with a "LayeredBloomFilter" from > commons-collections v4.5 > > Define the producer.id.quota.window.size.seconds to be the length of time > that a Bloom filter of PIDs will exist. > Define a new configuration option "producer.id.quota.window.count" as the > number of windows active in window.size.seconds. > > Define the "Shape" (See commons-collections bloomfilters v4.5) of the > bloom filter from the average number of PIDs expected in > window.size.seconds/window.count (call this N) and the probability of false > positives (call this P). Due to the way the LayeredBloomFilter works the > number of items can be a lower number than the max. I'll explain that in a > minute. > > The LayeredBloomFilter implements the standard BloomFilter interface but > internally keeps an ordered list of filters (called layers) from oldest > created to newest. It adds new layers when a specified Predicate > (checkExtend) returns true. It will remove filters as defined by a > specified Consumer (filterCleanup). > > Everytime a BloomFilter is merged into the LayeredBloomFilter the filter > checks to the "checkExtend" predicate. If it fires the "filterCleanup" is > called to remove any layers that should be removed and a new layer is added. > > Define the layers of the LayeredBloomFilter to comprise a standard > BloomFilter and an associated expiration timestamp. > > We can thus define > > - "checkExtend" to require a new layer window.size.seconds / > window.count seconds or when the current layer contains shape.N items. > - "filterCleanup" to start at the head of the list of layers and > remove any expired filters, usually 0, every window.size.seconds 1, > infrequently more than 1. > > This system will correctly handle bursty loads. There are 3 cases to > consider: > > 1. If the producer is producing fewer than shape.N PIDs the layer will > not fill up before the next layer is added. > 2. If the producer is producing shape.N PIDs the layer will be > processed as either a 1 or a 3 depending on system timings. > 3. If the producer is producing more than shape.N PIDs the layer will > fill up and a new layer will be created with an expiration timestamp > window.size.seconds from when it was created. This is the case that leads > to the filterCleanup infrequently having more than 1 layer to remove. > > The last case to consider is if a producer stops generating PIDs, in this > case we should walk the map of producers, call "filterCleanup", and then > check to see if the LayeredBloomFilter is empty. If so, remove it from the > map. It will be empty if the producer has not produced a PID for > window.size.seconds. > > I have this solution mostly coded, though I must admit I do not know where > to plugin the ProducerIdQuotaManager defined in the KIP > > Claude >
