Records integer values, and provides stable interval Histogram samples from live recorded data without interrupting or stalling active recording of values. Each interval histogram provided contains all value counts accumulated since the previous interval histogram was taken.

This pattern is commonly used in logging interval histogram information while recording is ongoing.

SingleWriterRecorder expects only a single thread (the "single writer") to call SingleWriterRecorder#recordValue or SingleWriterRecorder#recordValueWithExpectedInterval at any point in time. It DOES NOT safely support concurrent recording calls. Recording calls are wait-free on architectures that support atomic increment operations, and re lock-free on architectures that do not. *

A common pattern for using a SingleWriterRecorder looks like this:


SingleWriterRecorder recorder = new SingleWriterRecorder(2); // Two decimal point accuracy
Histogram intervalHistogram = null;
...
[start of some loop construct that periodically wants to grab an interval histogram]
  ...
  // Get interval histogram, recycling previous interval histogram:
  intervalHistogram = recorder.getIntervalHistogram(intervalHistogram);
  histogramLogWriter.outputIntervalHistogram(intervalHistogram);
  ...
[end of loop construct]

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	SingleWriterRecorder.InternalHistogram
private static class	SingleWriterRecorder.PackedInternalHistogram

Field Summary

Modifier and Type	Field and Description
private volatile Histogram	activeHistogram
private Histogram	inactiveHistogram
private final long	instanceId
private static AtomicLong	instanceIdSequencer
private final WriterReaderPhaser	recordingPhaser

Constructor Summary

Access	Constructor and Description
public	SingleWriterRecorder(final int 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. numberOfSignificantValueDigits, final boolean Specifies whether the recorder will uses a packed internal representation or not. packed) Construct an auto-resizing `SingleWriterRecorder` with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue.
public	SingleWriterRecorder(final int 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. numberOfSignificantValueDigits) Construct an auto-resizing `SingleWriterRecorder` with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue.
public	SingleWriterRecorder(final long The highest value to be tracked by the histogram. Must be a positive integer that is >= 2. highestTrackableValue, final int 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. numberOfSignificantValueDigits) Construct a `SingleWriterRecorder` given the highest value to be tracked and a number of significant decimal digits.
public	SingleWriterRecorder(final long 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. lowestDiscernibleValue, final long The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue). highestTrackableValue, final int 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. numberOfSignificantValueDigits) Construct a `SingleWriterRecorder` given the Lowest and highest values to be tracked and a number of significant decimal digits.

Method Summary

Modifier and Type	Method and Description
public synchronized Histogram	Returns: a histogram containing the value counts accumulated since the last interval histogram was taken. getIntervalHistogram() Get a new instance of an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
public synchronized Histogram	Returns: a histogram containing the value counts accumulated since the last interval histogram was taken. getIntervalHistogram(Histogram a previously returned interval histogram (from this instance of `SingleWriterRecorder`) that may be recycled to avoid allocation and copy operations. histogramToRecycle) Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
public synchronized Histogram	Returns: a histogram containing the value counts accumulated since the last interval histogram was taken. getIntervalHistogram(Histogram a previously returned interval histogram that may be recycled to avoid allocation and copy operations. histogramToRecycle, boolean if true, will only allow recycling of histograms previously returned from this instance of `SingleWriterRecorder`. If false, will allow recycling histograms previously returned by other instances of `SingleWriterRecorder`. enforeContainingInstance) Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
public synchronized void	getIntervalHistogramInto(Histogram the histogram into which the interval histogram's data should be copied targetHistogram) Place a copy of the value counts accumulated since accumulated (since the last interval histogram was taken) into `targetHistogram`.
private void	performIntervalSample()
public void	recordValue(final long the value to record value) Implements org.HdrHistogram.ValueRecorder.recordValue. Record a value
public void	recordValueWithCount(final long The value to be recorded value, final long The number of occurrences of this value to record count) Implements org.HdrHistogram.ValueRecorder.recordValueWithCount. Record a value in the histogram (adding to the value's current count)
public void	recordValueWithExpectedInterval(final long The value to record value, final long If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples expectedIntervalBetweenValueSamples) Implements org.HdrHistogram.ValueRecorder.recordValueWithExpectedInterval. Record a value To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, Histogram will auto-generate an additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records.
public synchronized void	reset() Implements org.HdrHistogram.ValueRecorder.reset. Reset any value counts accumulated thus far.
private void	validateFitAsReplacementHistogram(Histogram replacementHistogram, boolean enforeContainingInstance)

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

activeHistogram	back to summary
private volatile Histogram activeHistogram

inactiveHistogram	back to summary
private Histogram inactiveHistogram

instanceId	back to summary
private final long instanceId

instanceIdSequencer	back to summary
private static AtomicLong instanceIdSequencer

recordingPhaser	back to summary
private final WriterReaderPhaser recordingPhaser

Constructor Detail

SingleWriterRecorder back to summary

SingleWriterRecorder	back to summary
public SingleWriterRecorder(final int numberOfSignificantValueDigits, final boolean packed) Construct an auto-resizing `SingleWriterRecorder` 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). Depending on the valuer of the `packed` parameter `SingleWriterRecorder` can be configuired to track value counts in a packed internal representation optimized for typical histogram recoded values are sparse in the value range and tend to be incremented in small unit counts. This packed representation tends to require significantly smaller amounts of stoarge when compared to unpacked representations, but can incur additional recording cost due to resizing and repacking operations that may occur as previously unrecorded values are encountered. Parameters numberOfSignificantValueDigits:int 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. packed:boolean Specifies whether the recorder will uses a packed internal representation or not.

public SingleWriterRecorder(final int numberOfSignificantValueDigits, final boolean packed)

Construct an auto-resizing SingleWriterRecorder 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).

Depending on the valuer of the packed parameter SingleWriterRecorder can be configuired to track value counts in a packed internal representation optimized for typical histogram recoded values are sparse in the value range and tend to be incremented in small unit counts. This packed representation tends to require significantly smaller amounts of stoarge when compared to unpacked representations, but can incur additional recording cost due to resizing and repacking operations that may occur as previously unrecorded values are encountered.

Parameters

numberOfSignificantValueDigits:int: 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.
packed:boolean: Specifies whether the recorder will uses a packed internal representation or not.

SingleWriterRecorder back to summary

SingleWriterRecorder	back to summary
public SingleWriterRecorder(final int numberOfSignificantValueDigits) Construct an auto-resizing `SingleWriterRecorder` 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:int 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.

public SingleWriterRecorder(final int numberOfSignificantValueDigits)

Construct an auto-resizing SingleWriterRecorder 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:int: 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.

SingleWriterRecorder back to summary

SingleWriterRecorder	back to summary
public SingleWriterRecorder(final long highestTrackableValue, final int numberOfSignificantValueDigits) Construct a `SingleWriterRecorder` 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:long The highest value to be tracked by the histogram. Must be a positive integer that is >= 2. numberOfSignificantValueDigits:int 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.

public SingleWriterRecorder(final long highestTrackableValue, final int numberOfSignificantValueDigits)

Construct a SingleWriterRecorder 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:long: The highest value to be tracked by the histogram. Must be a positive integer that is >= 2.
numberOfSignificantValueDigits:int: 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.

SingleWriterRecorder back to summary

SingleWriterRecorder	back to summary
public SingleWriterRecorder(final long lowestDiscernibleValue, final long highestTrackableValue, final int numberOfSignificantValueDigits) Construct a `SingleWriterRecorder` 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:long 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:long The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue). numberOfSignificantValueDigits:int 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.

public SingleWriterRecorder(final long lowestDiscernibleValue, final long highestTrackableValue, final int numberOfSignificantValueDigits)

Construct a SingleWriterRecorder 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:long: 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:long: The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue).
numberOfSignificantValueDigits:int: 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.

Method Detail

getIntervalHistogram back to summary

getIntervalHistogram	back to summary
public synchronized Histogram getIntervalHistogram() Get a new instance of an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken. Calling `getIntervalHistogram()` will reset the value counts, and start accumulating value counts for the next interval. Returns:Histogram a histogram containing the value counts accumulated since the last interval histogram was taken.

public synchronized Histogram getIntervalHistogram()

Get a new instance of an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

Calling getIntervalHistogram() will reset the value counts, and start accumulating value counts for the next interval.

Returns:Histogram: a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogram back to summary

getIntervalHistogram	back to summary
public synchronized Histogram getIntervalHistogram(Histogram histogramToRecycle) Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken. `getIntervalHistogram(histogramToRecycle)` accepts a previously returned interval histogram that can be recycled internally to avoid allocation and content copying operations, and is therefore significantly more efficient for repeated use than `SingleWriterRecorder#getIntervalHistogram()` and `getIntervalHistogramInto()`. The provided `histogramToRecycle` must be either be null or an interval histogram returned by a previous call to `getIntervalHistogram(histogramToRecycle)` or `SingleWriterRecorder#getIntervalHistogram()`. Note The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined. Calling `getIntervalHistogram(histogramToRecycle)` will reset the value counts, and start accumulating value counts for the next interval Parameters histogramToRecycle:Histogram a previously returned interval histogram (from this instance of `SingleWriterRecorder`) that may be recycled to avoid allocation and copy operations. Returns:Histogram a histogram containing the value counts accumulated since the last interval histogram was taken.

public synchronized Histogram getIntervalHistogram(Histogram histogramToRecycle)

Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

getIntervalHistogram(histogramToRecycle) accepts a previously returned interval histogram that can be recycled internally to avoid allocation and content copying operations, and is therefore significantly more efficient for repeated use than SingleWriterRecorder#getIntervalHistogram() and getIntervalHistogramInto(). The provided histogramToRecycle must be either be null or an interval histogram returned by a previous call to getIntervalHistogram(histogramToRecycle) or SingleWriterRecorder#getIntervalHistogram().

Note

The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined.

Calling getIntervalHistogram(histogramToRecycle) will reset the value counts, and start accumulating value counts for the next interval

Parameters

histogramToRecycle:Histogram: a previously returned interval histogram (from this instance of SingleWriterRecorder) that may be recycled to avoid allocation and copy operations.

Returns:Histogram

a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogram back to summary

getIntervalHistogram	back to summary
public synchronized Histogram getIntervalHistogram(Histogram histogramToRecycle, boolean enforeContainingInstance) Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken. `getIntervalHistogram(histogramToRecycle)` accepts a previously returned interval histogram that can be recycled internally to avoid allocation and content copying operations, and is therefore significantly more efficient for repeated use than `SingleWriterRecorder#getIntervalHistogram()` and `getIntervalHistogramInto()`. The provided `histogramToRecycle` must be either be null or an interval histogram returned by a previous call to `getIntervalHistogram(histogramToRecycle)` or `SingleWriterRecorder#getIntervalHistogram()`. Note The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined. Calling `getIntervalHistogram(histogramToRecycle)` will reset the value counts, and start accumulating value counts for the next interval Parameters histogramToRecycle:Histogram a previously returned interval histogram that may be recycled to avoid allocation and copy operations. enforeContainingInstance:boolean if true, will only allow recycling of histograms previously returned from this instance of `SingleWriterRecorder`. If false, will allow recycling histograms previously returned by other instances of `SingleWriterRecorder`. Returns:Histogram a histogram containing the value counts accumulated since the last interval histogram was taken.

public synchronized Histogram getIntervalHistogram(Histogram histogramToRecycle, boolean enforeContainingInstance)

Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

Note

The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined.

Calling getIntervalHistogram(histogramToRecycle) will reset the value counts, and start accumulating value counts for the next interval

Parameters

histogramToRecycle:Histogram: a previously returned interval histogram that may be recycled to avoid allocation and copy operations.
enforeContainingInstance:boolean: if true, will only allow recycling of histograms previously returned from this instance of SingleWriterRecorder. If false, will allow recycling histograms previously returned by other instances of SingleWriterRecorder.

Returns:Histogram

a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogramInto back to summary

getIntervalHistogramInto	back to summary
public synchronized void getIntervalHistogramInto(Histogram targetHistogram) Place a copy of the value counts accumulated since accumulated (since the last interval histogram was taken) into `targetHistogram`. Calling `getIntervalHistogramInto(targetHistogram)` will reset the value counts, and start accumulating value counts for the next interval. Parameters targetHistogram:Histogram the histogram into which the interval histogram's data should be copied

public synchronized void getIntervalHistogramInto(Histogram targetHistogram)

Place a copy of the value counts accumulated since accumulated (since the last interval histogram was taken) into targetHistogram. Calling getIntervalHistogramInto(targetHistogram) will reset the value counts, and start accumulating value counts for the next interval.

Parameters

targetHistogram:Histogram: the histogram into which the interval histogram's data should be copied

performIntervalSample	back to summary
private void performIntervalSample()

recordValue	back to summary
public void recordValue(final long value) Implements org.HdrHistogram.ValueRecorder.recordValue. Record a value Parameters value:long the value to record Annotations @Override Exceptions ArrayIndexOutOfBoundsException: (may throw) if value is exceeds highestTrackableValue

recordValue

back to summary

public void recordValue(final long value)

Implements org.HdrHistogram.ValueRecorder.recordValue.

Record a value

Parameters

value:long: the value to record

Annotations

@Override

Exceptions

ArrayIndexOutOfBoundsException:: (may throw) if value is exceeds highestTrackableValue

recordValueWithCount	back to summary
public void recordValueWithCount(final long value, final long count) throws ArrayIndexOutOfBoundsException Implements org.HdrHistogram.ValueRecorder.recordValueWithCount. Record a value in the histogram (adding to the value's current count) Parameters value:long The value to be recorded count:long The number of occurrences of this value to record Annotations @Override Exceptions ArrayIndexOutOfBoundsException: (may throw) if value is exceeds highestTrackableValue

recordValueWithCount

back to summary

public void recordValueWithCount(final long value, final long count) throws ArrayIndexOutOfBoundsException

Implements org.HdrHistogram.ValueRecorder.recordValueWithCount.

Record a value in the histogram (adding to the value's current count)

Parameters

value:long: The value to be recorded
count:long: The number of occurrences of this value to record

Annotations

@Override

Exceptions

ArrayIndexOutOfBoundsException:: (may throw) if value is exceeds highestTrackableValue

recordValueWithExpectedInterval back to summary

recordValueWithExpectedInterval	back to summary
public void recordValueWithExpectedInterval(final long value, final long expectedIntervalBetweenValueSamples) throws ArrayIndexOutOfBoundsException Implements org.HdrHistogram.ValueRecorder.recordValueWithExpectedInterval. Record a value To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, Histogram will auto-generate an additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records. See related notes `AbstractHistogram#recordValueWithExpectedInterval(long, long)` for more explanations about coordinated omission and expected interval correction. * Parameters value:long The value to record expectedIntervalBetweenValueSamples:long If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples Annotations @Override Exceptions ArrayIndexOutOfBoundsException: (may throw) if value is exceeds highestTrackableValue

public void recordValueWithExpectedInterval(final long value, final long expectedIntervalBetweenValueSamples) throws ArrayIndexOutOfBoundsException

Implements org.HdrHistogram.ValueRecorder.recordValueWithExpectedInterval.

Record a value

To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, Histogram will auto-generate an additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records.

See related notes AbstractHistogram#recordValueWithExpectedInterval(long, long) for more explanations about coordinated omission and expected interval correction. *

Parameters

value:long: The value to record
expectedIntervalBetweenValueSamples:long: If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples

Annotations

@Override

Exceptions

ArrayIndexOutOfBoundsException:: (may throw) if value is exceeds highestTrackableValue

reset	back to summary
public synchronized void reset() Implements org.HdrHistogram.ValueRecorder.reset. Reset any value counts accumulated thus far. Annotations @Override

reset

back to summary

public synchronized void reset()

Implements org.HdrHistogram.ValueRecorder.reset.

Reset any value counts accumulated thus far.

Annotations

@Override

validateFitAsReplacementHistogram	back to summary
private void validateFitAsReplacementHistogram(Histogram replacementHistogram, boolean enforeContainingInstance)

org.HdrHistogram back to summary

private Class SingleWriterRecorder.InternalHistogram

Class Inheritance

extends Histogram

java.lang.Object
org.HdrHistogram.EncodableHistogram
org.HdrHistogram.AbstractHistogramBase
org.HdrHistogram.AbstractHistogram
org.HdrHistogram.Histogram
org.HdrHistogram.SingleWriterRecorder.InternalHistogram

Field Summary

Modifier and Type	Field and Description
private final long	containingInstanceId

Inherited from org.HdrHistogram.Histogram:: counts normalizingIndexOffset totalCount

Constructor Summary

Access	Constructor and Description
private	InternalHistogram(long id, int numberOfSignificantValueDigits)
private	InternalHistogram(long id, long lowestDiscernibleValue, long highestTrackableValue, int numberOfSignificantValueDigits)
private	InternalHistogram(SingleWriterRecorder.InternalHistogram source)

Method Summary

Field Detail

containingInstanceId	back to summary
private final long containingInstanceId

Constructor Detail

InternalHistogram	back to summary
private InternalHistogram(long id, int numberOfSignificantValueDigits)

InternalHistogram	back to summary
private InternalHistogram(long id, long lowestDiscernibleValue, long highestTrackableValue, int numberOfSignificantValueDigits)

InternalHistogram	back to summary
private InternalHistogram(SingleWriterRecorder.InternalHistogram source)

public Class SingleWriterRecorder

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class SingleWriterRecorder.InternalHistogram

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

private Class SingleWriterRecorder.PackedInternalHistogram

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail