Struct ChangelogDrainer 

pub struct ChangelogDrainer { /* private fields */ }

Drains a Ring 0 StateChangelogBuffer from Ring 1.

The drainer is the consumer side of the SPSC changelog buffer. It pops entries to relieve Ring 0 backpressure and tracks metadata for observability. Pending entries are cleared after each successful checkpoint via clear_pending().

Implementations

impl ChangelogDrainer

pub fn new(buffer: Arc<StateChangelogBuffer>, max_batch_size: usize) -> Self

Creates a new drainer for the given changelog buffer.

pub fn with_max_pending(self, max_pending: usize) -> Self

Sets the upper bound on pending entries.

When pending exceeds this limit during drain(), older entries are discarded to prevent unbounded memory growth.

pub fn drain(&mut self) -> usize

Drains available entries from the buffer into the pending batch.

If pending is at the max_pending limit, the oldest half of pending entries are discarded to make room. Returns the number of new entries drained from the buffer.

pub fn take_pending(&mut self) -> Vec<StateChangelogEntry>

Takes the pending batch, leaving an empty pending buffer.

After calling this, the drainer’s pending buffer is cleared and ready to accumulate more entries. The allocation is NOT reused.

pub fn clear_pending(&mut self)

Clears the pending buffer, reusing the existing allocation.

Call this after a successful checkpoint to release the metadata entries — they’re no longer needed once the checkpoint has captured the full state.

pub fn pending_count(&self) -> usize

Returns the number of pending (un-taken) entries.

pub fn pending(&self) -> &[StateChangelogEntry]

Returns a reference to the pending entries.

pub fn total_drained(&self) -> u64

Returns the total number of entries drained over the drainer’s lifetime.

pub fn buffer(&self) -> &StateChangelogBuffer

Returns a reference to the underlying changelog buffer.

Trait Implementations

impl Debug for ChangelogDrainer

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.