Class OffsetEpochNanoClock

java.lang.Object
org.agrona.concurrent.OffsetEpochNanoClock
All Implemented Interfaces:
EpochNanoClock

public class OffsetEpochNanoClock extends Object implements EpochNanoClock
An accurate, zero-gc, pure-java, EpochNanoClock that calculates an initial epoch nano time based on System.currentTimeMillis() and then uses that offset to adjust the return value of System.nanoTime() to the UNIX epoch.

The sample() method can be used in order to reset these initial values if your system clock gets updated.

This class can be used from multiple threads safely.

See Also:
  • Field Details

    • DEFAULT_MAX_MEASUREMENT_RETRIES

      private static final int DEFAULT_MAX_MEASUREMENT_RETRIES
      See Also:
    • DEFAULT_MEASUREMENT_THRESHOLD_NS

      private static final long DEFAULT_MEASUREMENT_THRESHOLD_NS
      See Also:
    • DEFAULT_RESAMPLE_INTERVAL_NS

      private static final long DEFAULT_RESAMPLE_INTERVAL_NS
    • maxMeasurementRetries

      private final int maxMeasurementRetries
    • measurementThresholdNs

      private final long measurementThresholdNs
    • resampleIntervalNs

      private final long resampleIntervalNs
    • timeFields

      private volatile OffsetEpochNanoClock.TimeFields timeFields
  • Constructor Details

    • OffsetEpochNanoClock

      public OffsetEpochNanoClock()
      Constructs the clock with default configuration.
    • OffsetEpochNanoClock

      public OffsetEpochNanoClock(int maxMeasurementRetries, long measurementThresholdNs, long resampleIntervalNs)
      Constructs the clock with custom configuration parameters.
      Parameters:
      maxMeasurementRetries - the maximum number of times that this clock will attempt to re-sample the initial time values.
      measurementThresholdNs - the desired accuracy window for the initial clock samples.
      resampleIntervalNs - the desired interval before the samples are automatically recalculated. The seed recalculation enables the system to minimise clock drift if the system clock is updated.
  • Method Details

    • sample

      public void sample()
      Explicitly resample the initial seeds.
    • nanoTime

      public long nanoTime()
      Time in nanoseconds since 1 Jan 1970 UTC.
      Specified by:
      nanoTime in interface EpochNanoClock
      Returns:
      the number of nanoseconds since 1 Jan 1970 UTC.
    • isWithinThreshold

      public boolean isWithinThreshold()
      Gets whether the clock sampled the initial time offset accurately.
      Returns:
      true if the clock sampled the initial time offset accurately.