Struct FinalizedTransactionsCache 

pub struct FinalizedTransactionsCache { /* private fields */ }

An advisory set of recently finalized transaction digests, used by the transaction voting path to short-circuit re-voting on already-finalized transactions (AuthorityPerEpochStore::is_recently_finalized).

Workload: a single writer (the consensus commit handler, ~one insert per finalized transaction) and many concurrent readers (the voting path, one contains per submitted transaction across the whole RPC/network worker pool). This is the inverse of what a concurrent cache like moka optimizes for cheaply: moka’s per-insert maintenance dominated the single-threaded handler at high TPS, while its lock-free reads were not the constraint.

Membership is all the read path needs, so entries never need recency promotion on read — that lets readers take a shared lock and run concurrently. Eviction is generational (FIFO): inserts fill current; once it reaches the per-generation capacity, current ages into previous (the prior previous is dropped) and a fresh current begins. contains checks both generations, so the most recent generation_capacity digests are always retained, and at most 2 * generation_capacity are held at once. FIFO is also a better fit than LRU here: a transaction is finalized once, so being repeatedly voted on should not extend how long it is “recently finalized”.

The cache is advisory — is_recently_finalized falls back to the executed-tx check — so the eventual-consistency and bounded-window behavior here is safe.

Implementations

impl FinalizedTransactionsCache

pub fn new(capacity: usize) -> Self

capacity is the target total number of digests retained; it is split across two generations so the live set stays within capacity.

pub fn insert(&self, tx_digest: TransactionDigest)

pub fn contains(&self, tx_digest: &TransactionDigest) -> bool