Trait raft::storage::Storage [−] [src]

pub trait Storage {
    fn initial_state(&self) -> Result<RaftState>;

    fn entries(&self, low: u64, high: u64, max_size: u64) -> Result<Vec<Entry>>;

    fn term(&self, idx: u64) -> Result<u64>;

    fn first_index(&self) -> Result<u64>;

    fn last_index(&self) -> Result<u64>;

    fn snapshot(&self) -> Result<Snapshot>;
}

Storage is an trait that may be implemented by the application to retrieve log entries from storage.

If any Storage method returns an error, the raft instance will become inoperable and refuse to paticipate in elections; the application is responsible for cleanup and recovery in this case.

Required Methods

initial_state returns the RaftState information

entries returns a slice of log entries in the range [lo,hi). max_size limits the total size of the log entries returned, but entries returns at least one entry if any.

term returns the term of entry idx, which must be in the range [first_index()-1, last_index()]. The term of the entry before first_index is retained for matching purpose even though the rest of that entry may not be available.

first_index returns the index of the first log entry that is possible available via entries (older entries have been incorporated into the latest snapshot; if storage only contains the dummy entry the first log entry is not available).

last_index returns the index of the last entry in the log.

snapshot returns the most recent snapshot. If snapshot is temporarily unavailable, it should return SnapshotTemporarilyUnavailable, so raft state machine could know that Storage needs some time to prepare snapshot and call snapshot later.

Implementors