kslack (Stream Processor)

Stream processor performs reordering of out-of-order events using K-Slack algorithm.

Syntax

reorder:kslack(<LONG> timestamp)
reorder:kslack(<LONG> timestamp, <LONG> timeout)
reorder:kslack(<LONG> timestamp, <BOOL> discard.late.arrival)
reorder:kslack(<LONG> timestamp, <LONG> timeout, <LONG> max.k)
reorder:kslack(<LONG> timestamp, <LONG> timeout, <BOOL> discard.late.arrival)
reorder:kslack(<LONG> timestamp, <LONG> timeout, <LONG> max.k, <BOOL> discard.late.arrival)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
timestamp	The event timestamp on which the events should be ordered.		LONG	No	Yes
timeout	A timeout value in milliseconds, where the buffered events who are older than the given timeout period get flushed every second.	-1 (timeout is infinite)	LONG	Yes	No
max.k	The maximum K-Slack window threshold (K parameter).	9,223,372,036,854,775,807 (The maximum Long value)	LONG	Yes	No
discard.late.arrival	If set to true the processor would discarded the out-of-order events arriving later than the K-Slack window, and in otherwise it allows the late arrivals to proceed.	false	BOOL	Yes	No

Example 1

CREATE STREAM StockStream (eventTime long, symbol string, volume long);

@info(name = 'kslackReorderingQuery')
INSERT INTO OutputStream
SELECT eventTime, symbol, volume
FROM StockStream#reorder:kslack(eventTime, 5000);

The kslackReorderingQuery processes stock events from the StockStream and outputs the reordered events to the OutputStream.

The #reorder:kslack(eventTime, 5000) part of the query is an event reordering extension. It reorders events based on the eventTime attribute value and forcefully flushes all events that have arrived older than the given timeout value (in this case, 5000 milliseconds or 5 seconds) every second.

The query's output includes the eventTime, symbol, and volume of the reordered events. The result is then directed to the OutputStream.