akslack (Stream Processor)
Stream processor performs reordering of out-of-order events optimized for a givenparameter using [AQ-K-Slack algorithm](http://dl.acm.org/citation.cfm?doid=2675743.2771828). This is best for reordering events on attributes those are used for aggregations.data .
Syntax
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field)
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field, <LONG> batch.size)
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field, <LONG> batch.size, <LONG> timeout)
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field, <LONG> batch.size, <LONG> timeout, <LONG> max.k)
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field, <LONG> batch.size, <LONG> timeout, <LONG> max.k, <BOOL> discard.late.arrival)
reorder:akslack(<LONG> timestamp, <INT|FLOAT|LONG|DOUBLE> correlation.field, <LONG> batch.size, <LONG> timeout, <LONG> max.k, <BOOL> discard.late.arrival, <DOUBLE> error.threshold, <DOUBLE> confidence.level)
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 | |
| correlation.field | By monitoring the changes in this field Alpha K-Slack dynamically optimises its behavior. This field is used to calculate the runtime window coverage threshold, which represents the upper limit set for unsuccessfully handled late arrivals. | INT FLOAT LONG DOUBLE | No | Yes | |
| batch.size | The parameter batch.size denotes the number of events that should be considered in the calculation of an alpha value. This should be greater than or equal to 15. | `10,000` | LONG | Yes | No |
| 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 |
| error.threshold | The error threshold to be applied in Alpha K-Slack algorithm. | `0.03` (3%) | DOUBLE | Yes | No |
| confidence.level | The confidence level to be applied in Alpha K-Slack algorithm. | `0.95` (95%) | DOUBLE | Yes | No |
Example 1
CREATE STREAM StockStream (eventTime long, symbol string, volume long);
@info(name = 'query1')
insert into OutputStream
select eventTime, symbol, sum(volume) as total
from StockStream#reorder:akslack(eventTime, volume, 20) WINDOW SLIDING_TIME(5 min);
The query reorders events based on the eventTime attribute value and optimises for aggregating volume attribute considering last 20 events.