C# Class Elders.Hystrix.NET.Util.HystrixRollingPercentile

Add values to a rolling window and retrieve percentile calculations such as median, 90th, 99th, etc.

The underlying data structure contains a circular array of buckets that "roll" over time.

For example, if the time window is configured to 60 seconds with 12 buckets of 5 seconds each, values will be captured in each 5 second bucket and rotate each 5 seconds.

This means that percentile calculations are for the "rolling window" of 55-60 seconds up to 5 seconds ago.

Each bucket will contain a circular array of long values and if more than the configured amount (1000 values for example) it will wrap around and overwrite values until time passes and a new bucket is allocated. This sampling approach for high volume metrics is done to conserve memory and reduce sorting time when calculating percentiles.

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Private Properties

Property	Type	Description
GetCurrentBucket	Bucket
HystrixRollingPercentile	System

Public Methods

Method	Description
AddValue ( ) : void	Add value (or values) to current bucket.
GetMean ( ) : int	Gets the mean (average) of all values in the current snapshot. This is not a percentile but often desired so captured and exposed here.
GetPercentile ( double percentile ) : int	Compute a percentile from the underlying rolling buckets of values. For performance reasons it maintains a single snapshot of the sorted values from all buckets that is re-generated each time the bucket rotates. This means that if a bucket is 5000 milliseconds, then this method will re-compute a percentile at most once every 5000 milliseconds.
HystrixRollingPercentile ( IHystrixProperty timeInMilliseconds, IHystrixProperty numberOfBuckets, IHystrixProperty bucketDataLength, IHystrixProperty enabled ) : System	Initializes a new instance of the HystrixRollingPercentile class.
Reset ( ) : void	Force a reset so that percentiles start being gathered from scratch.

Private Methods

Method	Description
GetCurrentBucket ( ) : Bucket	Gets the current bucket. If the time is after the window of the current bucket, a new one will be created. Internal because it's used in unit tests.
HystrixRollingPercentile ( ITime time, IHystrixProperty timeInMilliseconds, IHystrixProperty numberOfBuckets, IHystrixProperty bucketDataLength, IHystrixProperty enabled ) : System	Initializes a new instance of the HystrixRollingPercentile class.

Method Details

AddValue() public method

Add value (or values) to current bucket.

public AddValue ( ) : void
return	void

GetMean() public method

Gets the mean (average) of all values in the current snapshot. This is not a percentile but often desired so captured and exposed here.

public GetMean ( ) : int
return	int

GetPercentile() public method

Compute a percentile from the underlying rolling buckets of values.

For performance reasons it maintains a single snapshot of the sorted values from all buckets that is re-generated each time the bucket rotates.

This means that if a bucket is 5000 milliseconds, then this method will re-compute a percentile at most once every 5000 milliseconds.

public GetPercentile ( double percentile ) : int
percentile	double	Value such as 99 (99th percentile), 99.5 (99.5th percentile), 50 (median, 50th percentile) to compute and retrieve percentile from rolling buckets.
return	int

HystrixRollingPercentile() public method

Initializes a new instance of the HystrixRollingPercentile class.

public HystrixRollingPercentile ( IHystrixProperty timeInMilliseconds, IHystrixProperty numberOfBuckets, IHystrixProperty bucketDataLength, IHystrixProperty enabled ) : System
timeInMilliseconds	IHystrixProperty	Number of milliseconds of data that should be tracked.
numberOfBuckets	IHystrixProperty	Number of buckets that the time window should be divided into.
bucketDataLength	IHystrixProperty	Number of values stored in each bucket.
enabled	IHystrixProperty	Sets whether data should be tracked and percentiles be calculated.
return	System

Reset() public method

Force a reset so that percentiles start being gathered from scratch.

public Reset ( ) : void
return	void