Struct SlidingWindowOperator 

pub struct SlidingWindowOperator<A: Aggregator> { /* private fields */ }

Sliding window operator.

Processes events through overlapping, fixed-size time windows. Each event is assigned to multiple windows based on the slide interval. Results are emitted based on the configured EmitStrategy.

Emit Strategies

• OnWatermark (default): Emit when watermark passes window end
• Periodic: Emit intermediate results at intervals, final on watermark
• OnUpdate: Emit after every state update (can produce many outputs)

Late Data Handling

Events that arrive after window_end + allowed_lateness are considered late. Their behavior is controlled by LateDataConfig:

• Drop the event (default)
• Route to a named side output for separate processing

State Management

Window state is stored in the operator context’s state store using prefixed keys: slw:<window_id> - Accumulator state

Performance Considerations

Each event updates ceil(size / slide) windows. For example:

• 1-hour window, 15-minute slide = 4 windows per event
• 1-minute window, 10-second slide = 6 windows per event

State usage scales linearly with active windows.

Implementations

impl<A: Aggregator> SlidingWindowOperator<A>

where A::Acc: Archive + for<'a> RkyvSerialize<HighSerializer<AlignedVec, ArenaHandle<'a>, Error>>, <A::Acc as Archive>::Archived: for<'a> CheckBytes<HighValidator<'a, Error>> + RkyvDeserialize<A::Acc, HighDeserializer<Error>>,

pub fn new( assigner: SlidingWindowAssigner, aggregator: A, allowed_lateness: Duration, ) -> Self

Creates a new sliding window operator.

Arguments

• assigner - Window assigner for determining window boundaries
• aggregator - Aggregation function to apply within windows
• allowed_lateness - Grace period for late data after window close

Panics

Panics if allowed lateness does not fit in i64.

pub fn with_id( assigner: SlidingWindowAssigner, aggregator: A, allowed_lateness: Duration, operator_id: String, ) -> Self

Creates a new sliding window operator with a custom operator ID.

Panics

Panics if allowed lateness does not fit in i64.

pub fn set_emit_strategy(&mut self, strategy: EmitStrategy)

Sets the emit strategy for this window operator.

pub fn emit_strategy(&self) -> &EmitStrategy

Returns the current emit strategy.

pub fn set_late_data_config(&mut self, config: LateDataConfig)

Sets the late data handling configuration.

pub fn late_data_config(&self) -> &LateDataConfig

Returns the current late data configuration.

pub fn late_data_metrics(&self) -> &LateDataMetrics

Returns the late data metrics.

pub fn reset_late_data_metrics(&mut self)

Resets the late data metrics counters.

pub fn assigner(&self) -> &SlidingWindowAssigner

Returns the window assigner.

pub fn allowed_lateness_ms(&self) -> i64

Returns the allowed lateness in milliseconds.

Trait Implementations

impl<A: Aggregator> Operator for SlidingWindowOperator<A>

where A::Acc: 'static + Archive + for<'a> RkyvSerialize<HighSerializer<AlignedVec, ArenaHandle<'a>, Error>>, <A::Acc as Archive>::Archived: for<'a> CheckBytes<HighValidator<'a, Error>> + RkyvDeserialize<A::Acc, HighDeserializer<Error>>,

fn process(&mut self, event: &Event, ctx: &mut OperatorContext<'_>) -> OutputVec

Process an incoming event

fn on_timer(&mut self, timer: Timer, ctx: &mut OperatorContext<'_>) -> OutputVec

Handle timer expiration

fn checkpoint(&self) -> OperatorState

Checkpoint the operator’s state

fn restore(&mut self, state: OperatorState) -> Result<(), OperatorError>

Restore from a checkpoint