org.apache.beam.sdk.extensions.ordered

Interface EventExaminer<EventT,StateT extends MutableState<EventT,?>>

Type Parameters:

EventT -

StateT -

All Superinterfaces:

java.io.Serializable

public interface EventExaminer<EventT,StateT extends MutableState<EventT,?>>
extends java.io.Serializable

Classes extending this interface will be called by OrderedEventProcessor to examine every incoming event.

Method Summary

Modifier and Type	Method and Description
StateT	createStateOnInitialEvent(EventT event) If the event was the first event in the sequence, create the state to hold the required data needed for processing.
boolean	isInitialEvent(long sequenceNumber, EventT event) Is this event the first expected event for the given key and window?
boolean	isLastEvent(long sequenceNumber, EventT event) Is this event the last expected event for a given key and window?

Method Detail

isInitialEvent

boolean isInitialEvent(long sequenceNumber,
                       EventT event)

Is this event the first expected event for the given key and window?

Parameters:

sequenceNumber - the sequence number of the event as defined by the key of the input PCollection to OrderedEventProcessor

event - being processed

Returns:

true if this is the initial sequence.

createStateOnInitialEvent

StateT createStateOnInitialEvent(EventT event)

If the event was the first event in the sequence, create the state to hold the required data needed for processing. This data will be persisted.

Parameters:

event - the first event in the sequence.

Returns:

the state to persist.

isLastEvent

boolean isLastEvent(long sequenceNumber,
                    EventT event)

Is this event the last expected event for a given key and window?

Parameters:

sequenceNumber - of the event

event - being processed

Returns:

true if the last event. There are cases where it's impossible to know whether it's the last event. False should be returned in those cases.