feldera-buffer-cache

feldera-buffer-cache provides thread-safe in-memory caches used by Feldera's storage layer:

S3FifoCache wraps quick_cache's SOSP'23 S3-FIFO implementation behind a Feldera-oriented API: https://dl.acm.org/doi/10.1145/3600006.3613147

LruCache provides a mutex-protected LRU backend with the same high-level API.

BufferCacheBuilder constructs the foreground/background cache layout used by DBSP circuits.

API sketch

use feldera_buffer_cache::{CacheEntry, LruCache};

#[derive(Clone)]
struct Page(Vec<u8>);

impl CacheEntry for Page {
    fn cost(&self) -> usize {
        self.0.len()
    }
}

let cache = LruCache::<u64, Page>::new(64 << 20);
cache.insert(7, Page(vec![0; 4096]));

let page = cache.get(&7).expect("entry should be present");
assert_eq!(page.0.len(), 4096);
assert_eq!(cache.total_charge(), 4096);

Benchmarks

The throughput benchmark comparing LruCache and S3FifoCache lives under the dbsp bench targets:

cargo bench -p dbsp --bench buffer_cache -- --threads 1,2,4,8 --max-duration 10