Package org.HdrHistogram

Class ConcurrentHistogram

  • All Implemented Interfaces:
    java.io.Serializable, ValueRecorder
    Direct Known Subclasses:
    PackedConcurrentHistogram, Recorder.InternalConcurrentHistogram
    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

    • 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

      • ConcurrentHistogram

        ConcurrentHistogram​(AbstractHistogram source,
                    boolean allocateCountsArray)

      • ConcurrentHistogram

        ConcurrentHistogram​(long lowestDiscernibleValue,
                    long highestTrackableValue,
                    int numberOfSignificantValueDigits,
                    boolean allocateCountsArray)

    • Method Detail

      • recordConvertedDoubleValueWithCount

        public void recordConvertedDoubleValueWithCount​(double value,
                                                long count)
                                         throws java.lang.ArrayIndexOutOfBoundsException
        Overrides:
        recordConvertedDoubleValueWithCount in class AbstractHistogram
        Throws:
        java.lang.ArrayIndexOutOfBoundsException

      • setNormalizingIndexOffset

        private void setNormalizingIndexOffset​(int newNormalizingIndexOffset,
                                       int shiftedAmount,
                                       boolean lowestHalfBucketPopulated,
                                       double newIntegerToDoubleValueConversionRatio)

      • setNormalizingIndexOffsetForInactive

        private void setNormalizingIndexOffsetForInactive​(int newNormalizingIndexOffset,
                                                  int shiftedAmount,
                                                  boolean lowestHalfBucketPopulated,
                                                  double newIntegerToDoubleValueConversionRatio)

      • shiftLowestInactiveHalfBucketContentsLeft

        private void shiftLowestInactiveHalfBucketContentsLeft​(int shiftAmount,
                                                       int preShiftZeroIndex)

      • shiftNormalizingIndexByOffset

        void shiftNormalizingIndexByOffset​(int offsetToAdd,
                                   boolean lowestHalfBucketPopulated,
                                   double newIntegerToDoubleValueConversionRatio)
        Overrides:
        shiftNormalizingIndexByOffset in class Histogram

      • resize

        void resize​(long newHighestTrackableValue)
        Overrides:
        resize in class Histogram

      • 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

      • 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​(java.nio.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​(java.nio.ByteBuffer buffer,
                                                                 long minBarForHighestTrackableValue)
                                                          throws java.util.zip.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:
        java.util.zip.DataFormatException - on error parsing/decompressing the buffer

      • fromString

        public static ConcurrentHistogram fromString​(java.lang.String base64CompressedHistogramString)
                                      throws java.util.zip.DataFormatException
        Construct a new ConcurrentHistogram by decoding it from a String containing a base64 encoded compressed histogram representation.
        Parameters:
        base64CompressedHistogramString - A string containing a base64 encoding of a compressed histogram
        Returns:
        A ConcurrentHistogram decoded from the string
        Throws:
        java.util.zip.DataFormatException - on error parsing/decompressing the input

      • readObject

        private void readObject​(java.io.ObjectInputStream o)
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException