Package org.HdrHistogram

Class SingleWriterDoubleRecorder

  • All Implemented Interfaces:
    DoubleValueRecorder, IntervalHistogramProvider<DoubleHistogram>
    public class SingleWriterDoubleRecorder
extends Object
implements DoubleValueRecorder, IntervalHistogramProvider<DoubleHistogram>
    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]

    • 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 configured 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 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.

        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.