Struct SeqNumStore 

pub struct SeqNumStore { /* private fields */ }

Server-side durable store for the last-accepted seq_num per requester key.

Backed by one JSON file per requester key under {root}/. Writes are atomic (tmp-file + rename) and fsynced before rename so that a crash after bytes are transmitted cannot allow a replay.

Implementations

impl SeqNumStore

pub fn open(root: impl Into<PathBuf>) -> Self

pub fn for_data_dir(data_dir: impl AsRef<Path>) -> Self

pub fn for_group_fetch_data_dir(data_dir: impl AsRef<Path>) -> Self

pub fn last_seen( &self, requester_key_hex: &str, ) -> Result<u64, SeqNumStoreError>

Return the last accepted seq_num for this requester key, or 0 if the key has never been seen.

pub fn advance( &self, requester_key_hex: &str, new_seq_num: u64, ) -> Result<(), SeqNumStoreError>

Durably advance the stored seq_num for this requester key.

Fsync + atomic rename ensures the update survives a crash (R-ACCESS-11). Returns SeqNumStoreError::NotMonotonic if new_seq_num <= current.