Struct WriteAheadLog 

pub struct WriteAheadLog { /* private fields */ }

Write-Ahead Log implementation.

Implementations

impl WriteAheadLog

pub fn new<P: AsRef<Path>>( path: P, sync_interval: Duration, ) -> Result<Self, WalError>

Create a new WAL instance.

Arguments

• path - Path to the WAL file
• sync_interval - Interval for group commit

Errors

Returns WalError::Io if the file cannot be created or opened.

pub fn set_sync_on_write(&mut self, enabled: bool)

Enable sync on every write for stronger durability.

When enabled, every append() call triggers an immediate sync(), providing per-write durability at the cost of throughput (~10x lower). Without this, up to sync_interval of data may be lost on crash.

pub fn append(&mut self, entry: &WalEntry) -> Result<u64, WalError>

Append an entry to the WAL.

Record format: [length: 4 bytes][crc32: 4 bytes][data: length bytes]

Arguments

• entry - The entry to append

Errors

Returns WalError::Serialization if the entry cannot be serialized, or WalError::Io if the write fails.

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

Force sync to disk using fdatasync.

Uses sync_data() instead of sync_all() for better performance. This syncs file data without updating metadata, saving 50-100μs per sync.

Errors

Returns WalError::Io if the sync fails.

pub fn read_from(&self, position: u64) -> Result<WalReader, WalError>

Read entries from a specific position.

Arguments

• position - Starting position to read from

Errors

Returns WalError::Io if the file cannot be opened or seeked.

pub fn position(&self) -> u64

Get the current position in the log.

pub fn path(&self) -> &Path

Get the path to the WAL file.

pub fn truncate(&mut self, position: u64) -> Result<(), WalError>

Truncate the log at the specified position.

Used after successful checkpointing to remove old entries.

Errors

Returns WalError::Io if the truncation or file operations fail.

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

Repair the WAL by truncating to the last valid record.

This should be called during recovery to handle torn writes from crashes. It reads through the WAL, validates each record, and truncates at the first invalid record (torn write or corruption).

Returns

Returns Ok(valid_position) where valid_position is the end of the last valid record (and the new WAL length).

Errors

Returns WalError::Io if file operations fail.