Class SingleWriterDoubleRecorder

  • All Implemented Interfaces:
    DoubleValueRecorder

    public class SingleWriterDoubleRecorder
    extends java.lang.Object
    implements DoubleValueRecorder
    Records floating point values, and provides stable interval DoubleHistogram 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.

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

    A common pattern for using a SingleWriterDoubleRecorder looks like this:

    
     SingleWriterDoubleRecorder recorder = new SingleWriterDoubleRecorder(2); // Two decimal point accuracy
     DoubleHistogram 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]
     
    • Field Detail

      • instanceIdSequencer

        private static java.util.concurrent.atomic.AtomicLong instanceIdSequencer
      • instanceId

        private final long instanceId
    • Constructor Detail

      • SingleWriterDoubleRecorder

        public SingleWriterDoubleRecorder​(int numberOfSignificantValueDigits,
                                          boolean packed)
        Construct an auto-resizing SingleWriterDoubleRecorder using a precision stated as a number of significant decimal digits.

        Depending on the valuer of the packed parameter SingleWriterDoubleRecorder 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 - 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 - Specifies whether the recorder will uses a packed internal representation or not.
      • SingleWriterDoubleRecorder

        public SingleWriterDoubleRecorder​(int numberOfSignificantValueDigits)
        Construct an auto-resizing SingleWriterDoubleRecorder using a precision stated as a number of significant decimal digits.
        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.
      • SingleWriterDoubleRecorder

        public SingleWriterDoubleRecorder​(long highestToLowestValueRatio,
                                          int numberOfSignificantValueDigits)
        Construct a SingleWriterDoubleRecorder dynamic range of values to cover and a number of significant decimal digits.
        Parameters:
        highestToLowestValueRatio - specifies the dynamic range to use (as a ratio)
        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.
    • Method Detail

      • recordValue

        public void recordValue​(double value)
        Record a value
        Specified by:
        recordValue in interface DoubleValueRecorder
        Parameters:
        value - the value to record
        Throws:
        java.lang.ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue
      • recordValueWithCount

        public void recordValueWithCount​(double value,
                                         long count)
                                  throws java.lang.ArrayIndexOutOfBoundsException
        Record a value in the histogram (adding to the value's current count)
        Specified by:
        recordValueWithCount in interface DoubleValueRecorder
        Parameters:
        value - The value to be recorded
        count - The number of occurrences of this value to record
        Throws:
        java.lang.ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue
      • recordValueWithExpectedInterval

        public void recordValueWithExpectedInterval​(double value,
                                                    double expectedIntervalBetweenValueSamples)
                                             throws java.lang.ArrayIndexOutOfBoundsException
        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 DoubleHistogram.recordValueWithExpectedInterval(double, double) for more explanations about coordinated omission and expected interval correction. *

        Specified by:
        recordValueWithExpectedInterval in interface DoubleValueRecorder
        Parameters:
        value - The value to record
        expectedIntervalBetweenValueSamples - If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples
        Throws:
        java.lang.ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue
      • getIntervalHistogram

        public DoubleHistogram 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:
        a histogram containing the value counts accumulated since the last interval histogram was taken.
      • getIntervalHistogram

        public DoubleHistogram getIntervalHistogram​(DoubleHistogram 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 getIntervalHistogram() and getIntervalHistogramInto(). The provided histogramToRecycle must be either be null or an interval histogram returned by a previous call to getIntervalHistogram(histogramToRecycle) or 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 - a previously returned interval histogram (from this instance of SingleWriterDoubleRecorder) that may be recycled to avoid allocation and copy operations.
        Returns:
        a histogram containing the value counts accumulated since the last interval histogram was taken.
      • getIntervalHistogram

        public DoubleHistogram getIntervalHistogram​(DoubleHistogram 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 getIntervalHistogram() and getIntervalHistogramInto(). The provided histogramToRecycle must be either be null or an interval histogram returned by a previous call to getIntervalHistogram(histogramToRecycle) or 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 - a previously returned interval histogram that may be recycled to avoid allocation and copy operations.
        enforeContainingInstance - if true, will only allow recycling of histograms previously returned from this instance of SingleWriterDoubleRecorder. If false, will allow recycling histograms previously returned by other instances of SingleWriterDoubleRecorder.
        Returns:
        a histogram containing the value counts accumulated since the last interval histogram was taken.
      • getIntervalHistogramInto

        public void getIntervalHistogramInto​(DoubleHistogram 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 - the histogram into which the interval histogram's data should be copied
      • reset

        public void reset()
        Reset any value counts accumulated thus far.
        Specified by:
        reset in interface DoubleValueRecorder
      • performIntervalSample

        private void performIntervalSample()
      • validateFitAsReplacementHistogram

        private void validateFitAsReplacementHistogram​(DoubleHistogram replacementHistogram,
                                                       boolean enforeContainingInstance)