Struct WalWriteAheadLog 

pub struct WalWriteAheadLog { /* private fields */ }

In-memory, crash-recovery Write-Ahead Log.

All entries are serialised into a Vec<u8> segment buffer using a length-framed binary format with FNV-1a-64 checksums. The buffer can be exported, persisted externally, and then fed back into Self::recover on restart.

Example

use ipfrs_storage::write_ahead_log::{WalWriteAheadLog, WalConfig, WalOpType};

let mut wal = WalWriteAheadLog::new(WalConfig::default());
let seq = wal.write(b"hello".to_vec(), b"world".to_vec(), WalOpType::Put).unwrap();
assert!(seq > 0);
let data = wal.export_segment();
assert!(!data.is_empty());

Implementations

impl WalWriteAheadLog

pub fn new(config: WalConfig) -> Self

Creates a new WAL with the given configuration.

pub fn write( &mut self, key: Vec<u8>, value: Vec<u8>, op: WalOpType, ) -> Result<u64, WalError>

Writes a standalone (non-transactional) entry and returns its sequence number. Auto-checkpoints when the configured interval is reached.

pub fn begin_transaction(&mut self) -> u64

Begins a new transaction. Returns the transaction id.

pub fn write_tx( &mut self, tx_id: u64, key: Vec<u8>, value: Vec<u8>, op: WalOpType, ) -> Result<u64, WalError>

Writes an entry within a transaction. Returns the entry sequence number.

pub fn commit_transaction(&mut self, tx_id: u64) -> Result<(), WalError>

Commits a transaction: writes the Commit marker and marks it committed.

pub fn rollback_transaction(&mut self, tx_id: u64) -> Result<(), WalError>

Rolls back a transaction: writes the Rollback marker and marks it rolled back.

pub fn checkpoint(&mut self) -> Result<u64, WalError>

Creates a checkpoint entry and returns its sequence number.

All entries whose seq_num is less than or equal to the previous checkpoint sequence, and which do not belong to an active transaction, are removed from the in-memory entry list and the segment is rebuilt.

pub fn recover(data: &[u8]) -> Result<RecoveryResult, WalError>

Scans a raw byte buffer, decodes all valid entries, validates checksums, and returns a RecoveryResult.

Entries belonging to transactions that were never committed (i.e. no matching Commit entry appears) are discarded from the result.

pub fn replay(entries: &[WalEntry], handler: &mut dyn FnMut(&WalEntry)) -> usize

Iterates over the provided entries and calls handler for each committed Put or Delete entry. Returns the number of entries passed to the handler.

Standalone (tx_id == 0) Put/Delete entries are always replayed. Transactional entries are only replayed when their transaction’s Commit marker is present in entries.

pub fn export_segment(&self) -> Vec<u8>

Returns a clone of the current segment buffer.

pub fn stats(&self) -> WalStats

Returns a snapshot of current statistics.

pub fn truncate_before(&mut self, seq_num: u64) -> usize

Removes all entries with seq_num < seq_num from the in-memory list and rebuilds the segment buffer. Returns the number of entries removed.

pub fn entry_count(&self) -> usize

Returns the total number of in-memory entries.