Struct BarrierAligner 

pub struct BarrierAligner { /* private fields */ }

Buffers events at fan-in (MPSC) nodes until all upstream inputs have delivered their checkpoint barrier.

For nodes with a single input (expected_inputs == 1), alignment is immediate — no buffering occurs.

Implementations

impl BarrierAligner

pub fn new(expected_inputs: usize) -> Self

Creates a new barrier aligner for a node with expected_inputs upstream edges.

pub fn on_barrier( &mut self, source_node: NodeId, barrier: CheckpointBarrier, ) -> AlignmentResult

Processes a barrier arriving from source_node.

Returns AlignmentResult::Pending until all inputs have reported, then returns AlignmentResult::Aligned with the barrier and any buffered events sorted by event timestamp.

Cross-input ordering

Buffered events from different upstream inputs are merged and sorted by event.timestamp to ensure deterministic event-time ordering at fan-in nodes. Operators that require event-time ordering can rely on this guarantee for the post-alignment batch.

Panics

Panics if the internal barrier map is empty after insertion (should never happen).

pub fn buffer_if_aligned(&mut self, source_node: NodeId, event: Event) -> bool

Buffers an event from source_node if that source has already delivered its barrier for the current checkpoint.

Returns true if the event was buffered (source already aligned), false if the source has not yet delivered its barrier (event should be processed normally).

pub fn is_source_aligned(&self, source_node: NodeId) -> bool

Returns whether source_node has already delivered its barrier.

pub fn complete_checkpoint(&mut self)

Resets alignment state after a checkpoint completes.

pub fn barriers_received_count(&self) -> usize

Returns how many barriers have been received so far.

pub fn expected_inputs(&self) -> usize

Returns the expected number of upstream inputs.

Trait Implementations

impl Debug for BarrierAligner

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

Formats the value using the given formatter.