Struct WalBuffer 

pub struct WalBuffer { /* private fields */ }

In-memory WAL buffer for replication. Primary appends records here; replicas consume from it.

Each record payload is stored behind an Arc<[u8]> so fan-out to multiple replicas shares a single heap allocation per record (issue #832): a pull clones the Arc handle, never the bytes, so adding replicas does not multiply the primary’s send-buffer memory.

Implementations

impl WalBuffer

pub fn new(max_size: usize) -> Self

pub fn append(&self, lsn: u64, data: Vec<u8>)

Append a WAL record. Called by the storage engine after each write.

pub fn read_since( &self, since_lsn: u64, max_count: usize, ) -> Vec<(u64, Vec<u8>)>

Read records since the given LSN (exclusive), copying each payload into an owned Vec<u8>. Kept for callers (WAL archiving, retention bookkeeping) that need owned bytes; the per-replica fan-out path should prefer Self::read_since_shared to avoid copying.

pub fn read_since_shared( &self, since_lsn: u64, max_count: usize, ) -> Vec<(u64, Arc<[u8]>)>

Read records since the given LSN (exclusive) sharing the stored Arc<[u8]> payloads. Fan-out to N replicas clones only the reference-counted handles, so the buffer’s bytes are never duplicated per replica (issue #832).

pub fn read_since_shared_bounded( &self, since_lsn: u64, max_count: usize, max_payload_bytes: usize, ) -> Vec<(u64, Arc<[u8]>)>

Read shared records while bounding their aggregate payload bytes. The first matching record is returned even when it exceeds the byte budget so the transport can reject that indivisible record explicitly.

pub fn current_lsn(&self) -> u64

Current LSN.

pub fn set_current_lsn(&self, lsn: u64)

pub fn prune_through(&self, upto_lsn: u64)

pub fn oldest_lsn(&self) -> Option<u64>

Oldest available LSN (for gap detection).