Trait mz_persist::location::Log

pub trait Log {
    fn write_sync(&mut self, buf: Vec<u8>) -> Result<SeqNo, Error>;
    fn snapshot<F>(&self, logic: F) -> Result<Range<SeqNo>, Error>
    where
        F: FnMut(SeqNo, &[u8]) -> Result<(), Error>;
    fn truncate(&mut self, upper: SeqNo) -> Result<(), Error>;
    fn close(&mut self) -> Result<bool, Error>;
}

An abstraction over an append-only bytes log.

Each written entry is assigned a unique, incrementing SeqNo, which can be later used when draining data back out of the log.

• Invariant: Implementations are responsible for ensuring that they are exclusive writers to this location.

Required methods

fn write_sync(&mut self, buf: Vec<u8>) -> Result<SeqNo, Error>

Synchronously appends an entry.

TODO: Figure out our async story so we can batch up multiple of these into one disk flush.

fn snapshot<F>(&self, logic: F) -> Result<Range<SeqNo>, Error> where
    F: FnMut(SeqNo, &[u8]) -> Result<(), Error>, 

Returns a consistent snapshot of all written but not yet truncated entries.

• Invariant: all returned entries must have a sequence number within the declared [lower, upper) range of sequence numbers.

fn truncate(&mut self, upper: SeqNo) -> Result<(), Error>

Removes all entries with a SeqNo strictly less than the given upper bound.

fn close(&mut self) -> Result<bool, Error>

Synchronously closes the log, releasing exclusive-writer locks and causing all future commands to error.

Implementations must be idempotent. Returns true if the log had not previously been closed.

Implementors

impl Log for ErrorLog

impl Log for MemLog

impl<L: Log> Log for UnreliableLog<L>