Struct SegmentedWal 

pub struct SegmentedWal { /* private fields */ }

A segmented write-ahead log.

Manages a directory of WAL segment files. Records are appended to the active segment. When the active segment exceeds segment_target_size, a new segment is created automatically on the next append.

Implementations

impl SegmentedWal

pub fn open(config: SegmentedWalConfig) -> Result<Self>

Open or create a segmented WAL in the given directory.

On first startup, creates the directory and the first segment. On subsequent startups, discovers existing segments and opens the last one for continued appending.

pub fn set_encryption_ring(&mut self, ring: KeyRing) -> Result<()>

Set the encryption key ring. All subsequent records will be encrypted.

Must be called before the first append. Returns an error if records have already been written to the active segment.

pub fn configure_encryption_ring(&mut self, ring: KeyRing) -> Result<()>

Configure encryption for a newly created WAL or roll an already-open active segment before switching keys on restart.

pub fn encryption_ring(&self) -> Option<&KeyRing>

Get the encryption key ring (for replay decryption).

pub fn rotate_encryption_ring(&mut self, ring: KeyRing) -> Result<()>

Seal the active segment and start a new segment under ring. This is the only safe runtime key-rotation boundary because a segment’s encryption epoch and key are fixed by its preamble.

pub fn append( &mut self, record_type: u32, tenant_id: u64, vshard_id: u32, database_id: u64, payload: &[u8], ) -> Result<u64>

Append a record to the WAL. Returns the assigned LSN.

If the active segment has exceeded the target size, a new segment is created before appending. The rollover is transparent to the caller.

database_id is stored in header bytes 34-41. Pass 0 for the default database (backward-compatible with pre-existing records).

pub fn append_keyed( &mut self, target: RecordTarget, payload: &[u8], apply_key: u64, ) -> Result<u64>

Self::append for a record appended by the apply of the replicated proposal apply_key, carrying the event source in target (see crate::WalRecord::new_stamped).

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

Flush all buffered records and fsync the active segment.

pub fn seal_active_segment(&mut self) -> Result<()>

Seal the active segment and start the next one, so every record appended so far sits in a sealed segment. A no-op when the active segment holds no record.

pub fn next_lsn(&self) -> u64

The next LSN that will be assigned.

pub fn max_payload(&self) -> usize

The largest payload one record takes (see WalWriter::max_payload).

pub fn active_segment_first_lsn(&self) -> u64

First LSN of the active (currently written) segment.

pub fn wal_dir(&self) -> &Path

The WAL directory path.

pub fn truncate_before(&self, checkpoint_lsn: u64) -> Result<TruncateResult>

Truncate old WAL segments that are fully below the checkpoint LSN.

Only sealed (non-active) segments are eligible for deletion. The active segment is never deleted.

Returns the number of segments deleted and bytes reclaimed.

pub fn replay(&self) -> Result<Vec<WalRecord>>

Replay all committed records across all segments, in LSN order.

Used for crash recovery on startup. Payloads are returned as plaintext: this WAL’s own key ring is applied to every encrypted record.

pub fn replay_from(&self, from_lsn: u64) -> Result<Vec<WalRecord>>

Replay only records with LSN >= from_lsn.

Used when recovering from a checkpoint — records before the checkpoint LSN have already been applied from the snapshot.

Fails with WalError::ReplayBelowRetainedFloor when from_lsn names an LSN truncation has already deleted, rather than returning the shorter suffix that survives. Delegating to replay_from_limit_dir keeps that check — and the per-segment continuity and torn-tail checks — in one place instead of replaying everything and filtering afterwards.

pub fn replay_from_limit( &self, from_lsn: u64, max_records: usize, ) -> Result<(Vec<WalRecord>, bool)>

Paginated replay (delegates to standalone replay_from_limit_dir).

pub fn list_segments(&self) -> Result<Vec<SegmentMeta>>

List all segment metadata (for monitoring / operational tooling).

pub fn total_size_bytes(&self) -> Result<u64>

Total WAL size on disk across all segments.