com.github.rollingmetrics.hitratio

Class SmoothlyDecayingRollingHitRatio

java.lang.Object

com.github.rollingmetrics.hitratio.SmoothlyDecayingRollingHitRatio

All Implemented Interfaces:

HitRatio

public class SmoothlyDecayingRollingHitRatio
extends Object
implements HitRatio

The rolling time window hit-ratio implementation which resets its state by chunks. The unique properties which makes this hit-ratio probably the best "rolling time window" implementation are following:

• Sufficient performance about tens of millions concurrent writes and reads per second.
• Predictable and low memory consumption, the memory which consumed by hit-ratio does not depend from amount and frequency of writes.
• Perfectly user experience, the continuous observation does not see the sudden changes of sum. This property achieved by smoothly decaying of oldest chunk of hit-ratio.

Concurrency properties:

• Writing is lock-free.
• Ratio calculation is lock-free.

Usage recommendations:

• Only when you need in "rolling time window" semantic.

Performance considerations:

• You can consider writing speed as a constant. The write latency does not depend from count of chunk or frequency of chunk rotation.
• The writing depends only from level of contention between writers(internally hit-ratio implemented across AtomicLong).
• The huge count of chunk leads to the slower calculation of their ratio. So precision of getHitRatio conflicts with latency of getHitRatio. You need to choose meaningful values. For example 10 chunks will guarantee at least 90% accuracy and ten million reads per second.

See Also:

ResetOnSnapshotHitRatio, ResetPeriodicallyHitRatio, UniformHitRatio

Constructor Summary

Constructors

Constructor and Description
SmoothlyDecayingRollingHitRatio(Duration rollingWindow, int numberChunks) Constructs the chunked hit-ratio divided by numberChunks.
SmoothlyDecayingRollingHitRatio(Duration rollingWindow, int numberChunks, Ticker ticker)

Method Summary

Modifier and Type	Method and Description
int	getChunkCount()
double	getHitRatio() Returns the ratio between hits and misses
Duration	getRollingWindow()
String	toString()
void	update(int hitCount, int totalCount) Registers an result of bulk operations.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.github.rollingmetrics.hitratio.HitRatio

incrementHitCount, incrementMissCount

Constructor Detail

SmoothlyDecayingRollingHitRatio

public SmoothlyDecayingRollingHitRatio(Duration rollingWindow,
                                       int numberChunks)

Constructs the chunked hit-ratio divided by numberChunks. The hit-ratio will invalidate one chunk each time when rollingWindow/numberChunks millis has elapsed, except oldest chunk which invalidated continuously. The memory consumed by hit-ratio and latency of ratio calculation depend directly from numberChunks

Parameters:

rollingWindow - the rolling time window duration

numberChunks - The count of chunk to split

SmoothlyDecayingRollingHitRatio

public SmoothlyDecayingRollingHitRatio(Duration rollingWindow,
                                       int numberChunks,
                                       Ticker ticker)

Method Detail

getRollingWindow

public Duration getRollingWindow()

Returns:

the rolling window duration for this hit-ratio

getChunkCount

public int getChunkCount()

Returns:

the number of chunks

update

public void update(int hitCount,
                   int totalCount)

Description copied from interface: HitRatio

Registers an result of bulk operations.

Example of usage:

 
 Set<Something> cachedValues = cache.get(keys);
 hitRatio.update(cachedValues.size(), keys.size());
 
 

Specified by:

update in interface HitRatio

getHitRatio

public double getHitRatio()

Description copied from interface: HitRatio

Returns the ratio between hits and misses

Specified by:

getHitRatio in interface HitRatio

Returns:

the ratio between hits and misses

toString

public String toString()

Overrides:

toString in class Object