Class SlidingTimeWindowMetrics

  • All Implemented Interfaces:
    Metrics

    public class SlidingTimeWindowMetrics
    extends java.lang.Object
    implements Metrics
    A Metrics implementation is backed by a sliding time window that aggregates only the calls made in the last N seconds.

    The sliding time window is implemented with a circular array of N partial aggregations (buckets). If the time window size is 10 seconds, the circular array has always 10 partial aggregations (buckets). Every bucket aggregates the outcome of all calls which happen in a certain epoch second. (Partial aggregation) The head bucket of the circular array stores the call outcomes of the current epoch second. The other partial aggregations store the call outcomes of the previous N-1 epoch seconds.

    The sliding window does not store call outcomes (tuples) individually, but incrementally updates partial aggregations (bucket) and a total aggregation. The total total aggregation is updated incrementally when a new call outcome is recorded. When the oldest bucket is evicted, the partial total aggregation of that bucket is subtracted from the total aggregation. (Subtract-on-Evict)

    The time to retrieve a Snapshot is constant 0(1), since the Snapshot is pre-aggregated and is independent of the time window size. The space requirement (memory consumption) of this implementation should be nearly constant O(n), since the call outcomes (tuples) are not stored individually. Only N partial aggregations and 1 total total aggregation are created.

    • Constructor Detail

      • SlidingTimeWindowMetrics

        public SlidingTimeWindowMetrics​(int timeWindowSizeInSeconds,
                                        java.time.Clock clock)
        Creates a new SlidingTimeWindowMetrics with the given clock and window of time.
        Parameters:
        timeWindowSizeInSeconds - the window time size in seconds
        clock - the Clock to use
    • Method Detail

      • record

        public Snapshot record​(long duration,
                               java.util.concurrent.TimeUnit durationUnit,
                               Metrics.Outcome outcome)
        Description copied from interface: Metrics
        Records a call.
        Specified by:
        record in interface Metrics
        Parameters:
        duration - the duration of the call
        durationUnit - the time unit of the duration
        outcome - the outcome of the call
      • getSnapshot

        public Snapshot getSnapshot()
        Description copied from interface: Metrics
        Returns a snapshot.
        Specified by:
        getSnapshot in interface Metrics
        Returns:
        a snapshot