io.pravega.client.stream

Class ScalingPolicy

java.lang.Object

io.pravega.client.stream.ScalingPolicy

All Implemented Interfaces:

java.io.Serializable

public class ScalingPolicy
extends java.lang.Object
implements java.io.Serializable

A policy that specifies how the number of segments in a stream should scale over time.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ScalingPolicy.ScaleType

Constructor Summary

Constructors

Constructor and Description
ScalingPolicy()

Method Summary

Modifier and Type	Method and Description
static ScalingPolicy	byDataRate(int targetKBps, int scaleFactor, int minNumSegments) Create a scaling policy to configure a stream to scale up and down according to byte rate.
static ScalingPolicy	byEventRate(int targetRate, int scaleFactor, int minNumSegments) Create a scaling policy to configure a stream to scale up and down according to event rate.
static ScalingPolicy	fixed(int numSegments) Create a scaling policy to configure a stream to have a fixed number of segments.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ScalingPolicy

public ScalingPolicy()

Method Detail

fixed

public static ScalingPolicy fixed(int numSegments)

Create a scaling policy to configure a stream to have a fixed number of segments.

Parameters:

numSegments - Fixed number of segments for the stream.

Returns:

Scaling policy object.

byEventRate

public static ScalingPolicy byEventRate(int targetRate,
                                        int scaleFactor,
                                        int minNumSegments)

Create a scaling policy to configure a stream to scale up and down according to event rate. Pravega scales a stream segment up in the case that one of these conditions holds: - The two-minute rate is greater than 5x the target rate - The five-minute rate is greater than 2x the target rate - The ten-minute rate is greater than the target rate It scales a segment down (merges with a neighbor segment) in the case that both these conditions hold: - The two-, five-, ten-minute rate is smaller than the target rate - The twenty-minute rate is smaller than half of the target rate We additionally consider a cool-down period during which the segment is not considered for scaling. This period is determined by the configuration parameter autoScale.cooldownInSeconds; the default value is 10 minutes. The scale factor bounds the number of new segments that can be created upon a scaling event. In the case the controller computes the number of splits to be greater than the scale factor for a given scale-up event, the number of splits for the event is going to be equal to the scale factor. The policy is configured with a minimum number of segments for the stream, independent of the number of scale down events.

Parameters:

targetRate - Target rate in events per second to enable scaling events per segment.

scaleFactor - Maximum number of splits of a segment for a scale-up event.

minNumSegments - Minimum number of segments that a stream can have independent of the number of scale down events.

Returns:

Scaling policy object.

byDataRate

public static ScalingPolicy byDataRate(int targetKBps,
                                       int scaleFactor,
                                       int minNumSegments)

Create a scaling policy to configure a stream to scale up and down according to byte rate. Pravega scales a stream segment up in the case that one of these conditions holds: - The two-minute rate is greater than 5x the target rate - The five-minute rate is greater than 2x the target rate - The ten-minute rate is greater than the target rate It scales a segment down (merges with a neighbor segment) in the case that both these conditions hold: - The two-, five-, ten-minute rate is smaller than the target rate - The twenty-minute rate is smaller than half of the target rate We additionally consider a cool-down period during which the segment is not considered for scaling. This period is determined by the configuration parameter autoScale.cooldownInSeconds; the default value is 10 minutes. The scale factor bounds the number of new segments that can be created upon a scaling event. In the case the controller computes the number of splits to be greater than the scale factor for a given scale-up event, the number of splits for the event is going to be equal to the scale factor. The policy is configured with a minimum number of segments for a stream, independent of the number of scale down events.

Parameters:

targetKBps - Target rate in kilo bytes per second to enable scaling events per segment.

scaleFactor - Maximum number of splits of a segment for a scale-up event.

minNumSegments - Minimum number of segments that a stream can have independent of the number of scale down events.

Returns:

Scaling policy object.