org.HdrHistogram

Class ConcurrentHistogram

java.lang.Object

org.HdrHistogram.EncodableHistogram

org.HdrHistogram.AbstractHistogram

org.HdrHistogram.Histogram

org.HdrHistogram.ConcurrentHistogram

All Implemented Interfaces:

Serializable

public class ConcurrentHistogram
extends Histogram

An integer values High Dynamic Range (HDR) Histogram that supports safe concurrent recording operations.

A ConcurrentHistogram guarantees lossless recording of values into the histogram even when the histogram is updated by multiple threads, and supports auto-resize and shift operations that may result from or occur concurrently with other recording operations.

It is important to note that concurrent recording, auto-sizing, and value shifting are the only thread-safe behaviors provided by ConcurrentHistogram, and that it is not otherwise synchronized. Specifically, ConcurrentHistogram provides no implicit synchronization that would prevent the contents of the histogram from changing during queries, iterations, copies, or addition operations on the histogram. Callers wishing to make potentially concurrent, multi-threaded updates that would safely work in the presence of queries, copies, or additions of histogram objects should either take care to externally synchronize and/or order their access, use the SynchronizedHistogram variant, or (recommended) use Recorder or SingleWriterRecorder which are intended for this purpose.

Auto-resizing: When constructed with no specified value range range (or when auto-resize is turned on with AbstractHistogram.setAutoResize(boolean)) a Histogram will auto-resize its dynamic range to include recorded values as they are encountered. Note that recording calls that cause auto-resizing may take longer to execute, as resizing incurs allocation and copying of internal data structures.

See package description for org.HdrHistogram for details.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.HdrHistogram.AbstractHistogram

AbstractHistogram.AllValues, AbstractHistogram.LinearBucketValues, AbstractHistogram.LogarithmicBucketValues, AbstractHistogram.Percentiles, AbstractHistogram.RecordedValues

Constructor Summary

Constructors

Constructor and Description
ConcurrentHistogram(AbstractHistogram source) Construct a histogram with the same range settings as a given source histogram, duplicating the source's start/end timestamps (but NOT it's contents)
ConcurrentHistogram(int numberOfSignificantValueDigits) Construct an auto-resizing ConcurrentHistogram with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue.
ConcurrentHistogram(long highestTrackableValue, int numberOfSignificantValueDigits) Construct a ConcurrentHistogram given the Highest value to be tracked and a number of significant decimal digits.
ConcurrentHistogram(long lowestDiscernibleValue, long highestTrackableValue, int numberOfSignificantValueDigits) Construct a ConcurrentHistogram given the Lowest and Highest values to be tracked and a number of significant decimal digits.

Method Summary

Modifier and Type	Method and Description
ConcurrentHistogram	copy() Create a copy of this histogram, complete with data and everything.
ConcurrentHistogram	copyCorrectedForCoordinatedOmission(long expectedIntervalBetweenValueSamples) Get a copy of this histogram, corrected for coordinated omission.
static ConcurrentHistogram	decodeFromByteBuffer(ByteBuffer buffer, long minBarForHighestTrackableValue) Construct a new histogram by decoding it from a ByteBuffer.
static ConcurrentHistogram	decodeFromCompressedByteBuffer(ByteBuffer buffer, long minBarForHighestTrackableValue) Construct a new histogram by decoding it from a compressed form in a ByteBuffer.
long	getTotalCount() Get the total count of all recorded values in the histogram
void	setAutoResize(boolean autoResize) Control whether or not the histogram can auto-resize and auto-adjust it's highestTrackableValue

Methods inherited from class org.HdrHistogram.AbstractHistogram

add, addWhileCorrectingForCoordinatedOmission, allValues, copyInto, copyIntoCorrectedForCoordinatedOmission, encodeIntoByteBuffer, encodeIntoCompressedByteBuffer, encodeIntoCompressedByteBuffer, equals, getCountAtValue, getCountBetweenValues, getEndTimeStamp, getEstimatedFootprintInBytes, getHighestTrackableValue, getLowestDiscernibleValue, getMaxValue, getMaxValueAsDouble, getMean, getMinNonZeroValue, getMinValue, getNeededByteBufferCapacity, getNumberOfSignificantValueDigits, getPercentileAtOrBelowValue, getStartTimeStamp, getStdDeviation, getTag, getValueAtPercentile, hashCode, highestEquivalentValue, isAutoResize, linearBucketValues, logarithmicBucketValues, lowestEquivalentValue, medianEquivalentValue, nextNonEquivalentValue, outputPercentileDistribution, outputPercentileDistribution, outputPercentileDistribution, percentiles, recordedValues, recordValue, recordValue, recordValueWithCount, recordValueWithExpectedInterval, reset, setEndTimeStamp, setStartTimeStamp, setTag, shiftValuesLeft, shiftValuesRight, sizeOfEquivalentValueRange, subtract, valuesAreEquivalent

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcurrentHistogram

public ConcurrentHistogram(int numberOfSignificantValueDigits)

Construct an auto-resizing ConcurrentHistogram with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue. Can auto-resize up to track values up to (Long.MAX_VALUE / 2).

Parameters:

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

ConcurrentHistogram

public ConcurrentHistogram(long highestTrackableValue,
                           int numberOfSignificantValueDigits)

Construct a ConcurrentHistogram given the Highest value to be tracked and a number of significant decimal digits. The histogram will be constructed to implicitly track (distinguish from 0) values as low as 1.

Parameters:

highestTrackableValue - The highest value to be tracked by the histogram. Must be a positive integer that is >= 2.

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

ConcurrentHistogram

public ConcurrentHistogram(long lowestDiscernibleValue,
                           long highestTrackableValue,
                           int numberOfSignificantValueDigits)

Construct a ConcurrentHistogram given the Lowest and Highest values to be tracked and a number of significant decimal digits. Providing a lowestDiscernibleValue is useful is situations where the units used for the histogram's values are much smaller that the minimal accuracy required. E.g. when tracking time values stated in nanosecond units, where the minimal accuracy required is a microsecond, the proper value for lowestDiscernibleValue would be 1000.

Parameters:

lowestDiscernibleValue - The lowest value that can be tracked (distinguished from 0) by the histogram. Must be a positive integer that is >= 1. May be internally rounded down to nearest power of 2.

highestTrackableValue - The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue).

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

ConcurrentHistogram

public ConcurrentHistogram(AbstractHistogram source)

Construct a histogram with the same range settings as a given source histogram, duplicating the source's start/end timestamps (but NOT it's contents)

Parameters:

source - The source histogram to duplicate

Method Detail

setAutoResize

public void setAutoResize(boolean autoResize)

Description copied from class: AbstractHistogram

Control whether or not the histogram can auto-resize and auto-adjust it's highestTrackableValue

Overrides:

setAutoResize in class AbstractHistogram

Parameters:

autoResize - autoResize setting

copy

public ConcurrentHistogram copy()

Description copied from class: AbstractHistogram

Create a copy of this histogram, complete with data and everything.

Overrides:

copy in class Histogram

Returns:

A distinct copy of this histogram.

copyCorrectedForCoordinatedOmission

public ConcurrentHistogram copyCorrectedForCoordinatedOmission(long expectedIntervalBetweenValueSamples)

Description copied from class: AbstractHistogram

Get a copy of this histogram, corrected for coordinated omission.

To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, the new histogram will include an auto-generated additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records for each count found in the current histogram that is larger than the expectedIntervalBetweenValueSamples. Note: This is a post-correction method, as opposed to the at-recording correction method provided by recordValueWithExpectedInterval. The two methods are mutually exclusive, and only one of the two should be be used on a given data set to correct for the same coordinated omission issue. by

See notes in the description of the Histogram calls for an illustration of why this corrective behavior is important.

Overrides:

copyCorrectedForCoordinatedOmission in class Histogram

Parameters:

expectedIntervalBetweenValueSamples - If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples

Returns:

a copy of this histogram, corrected for coordinated omission.

getTotalCount

public long getTotalCount()

Description copied from class: AbstractHistogram

Get the total count of all recorded values in the histogram

Overrides:

getTotalCount in class Histogram

Returns:

the total count of all recorded values in the histogram

decodeFromByteBuffer

public static ConcurrentHistogram decodeFromByteBuffer(ByteBuffer buffer,
                                                       long minBarForHighestTrackableValue)

Construct a new histogram by decoding it from a ByteBuffer.

Parameters:

buffer - The buffer to decode from

minBarForHighestTrackableValue - Force highestTrackableValue to be set at least this high

Returns:

The newly constructed histogram

decodeFromCompressedByteBuffer

public static ConcurrentHistogram decodeFromCompressedByteBuffer(ByteBuffer buffer,
                                                                 long minBarForHighestTrackableValue)
                                                          throws DataFormatException

Construct a new histogram by decoding it from a compressed form in a ByteBuffer.

Parameters:

buffer - The buffer to decode from

minBarForHighestTrackableValue - Force highestTrackableValue to be set at least this high

Returns:

The newly constructed histogram

Throws:

DataFormatException - on error parsing/decompressing the buffer