Package org.HdrHistogram

Class PackedConcurrentHistogram

  • All Implemented Interfaces:
    Serializable, ValueRecorder
    public class PackedConcurrentHistogram
extends ConcurrentHistogram

    An integer values High Dynamic Range (HDR) Histogram that uses a packed internal representation and supports safe concurrent recording operations.

    A PackedConcurrentHistogram 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.

    PackedConcurrentHistogram tracks 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 storage 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.

    It is important to note that concurrent recording, auto-sizing, and value shifting are the only thread-safe behaviors provided by PackedConcurrentHistogram, and that it is not otherwise synchronized. Specifically, PackedConcurrentHistogram 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 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 PackedConcurrentHistogram 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

      • PackedConcurrentHistogram

        public PackedConcurrentHistogram​(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.

      • PackedConcurrentHistogram

        public PackedConcurrentHistogram​(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.

      • PackedConcurrentHistogram

        public PackedConcurrentHistogram​(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.

      • PackedConcurrentHistogram

        public PackedConcurrentHistogram​(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

      • copyCorrectedForCoordinatedOmission

        public PackedConcurrentHistogram 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 ConcurrentHistogram
        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 ConcurrentHistogram
        Returns:
        the total count of all recorded values in the histogram

      • decodeFromByteBuffer

        public static PackedConcurrentHistogram 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 PackedConcurrentHistogram 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

      • fromString

        public static PackedConcurrentHistogram fromString​(String base64CompressedHistogramString)
                                            throws 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:
        DataFormatException - on error parsing/decompressing the input