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/*
 * package-info.java
 * Written by Gil Tene of Azul Systems, and released to the public domain,
 * as explained at http://creativecommons.org/publicdomain/zero/1.0/
 */

/**
 * A latency stats tracking package
 * 
 * The LatencyUtils package includes useful utilities for tracking latencies. Especially in common in-process
 * recording scenarios, which can exhibit significant coordinated omission sensitivity without proper handling.
 * {@link org.LatencyUtils.LatencyStats} instances are used to track recorded latencies in the common
 * use case the often follow this pattern:
 *
 * 
 * 
 * LatencyStats myOpStats = new LatencyStats();
 * ...
 *
 * // During normal operation, record all operation latencies into a LatencyStats instance:
 *
 * long startTime = System.nanoTime();
 * // Perform operation:
 * doMyOperation(...);
 * // Record operation latency:
 * myOpStats.recordLatency(System.nanoTime() - startTime);
 * ...
 *
 * // Later, report on stats collected:
 * Histogram intervalHistogram = myOpStats.getIntervalHistogram();
 *
 * intervalHistogram.getHistogramData().outputPercentileDistribution(System.out, 1000000.0);
 *
 * 
 * 
 *
 * The problem
 * Latency tracking of in-process operations usually consists simple time sampling around a tracked operation.
 * E.g. a database read operation for which latency statistics are being developed may be surrounded by time
 * measurement operation immediately before and after the operation is performed, with the difference in
 * time recorded in some aggregate statistics gathering form (average, std. deviation, histogram,. etc.) which
 * is later used to report on the experienced latency behavior of the tracked operation.
 * 
 * The problem with this extremely common form of latency behavior tracking is that whenever pauses occur in
 * the system, latency statistics become significantly skewed toward falsely-optimistic values. This occurs in
 * two key ways:
 * 

 * When a pause occurs during a tracked operation, a single long recorded latency will appear in the recorded
 * values, with no long latencies associated with any pending requests that may be stalled by the pause.
 * When a pause occurs outside of the tracked operation (and outside of the tracked time window) no long
 * latency value would be recorded, even though any requested operation would be stalled by the pause.
 * 
 * 
 * The Solution
 * The {@link org.LatencyUtils.LatencyStats} class is designed for simple, drop-in use as a latency behavior
 * recording object in common in-process latency recording and tracking situations. LatencyStats includes
 * under-the-hood tracking and correction of pause effects, compensating for coordinated omission. It does
 * so by using pluggable pause detectors and interval estimators that together with
 * {@link org.LatencyUtils.LatencyStats} will transparently produce corrected histogram values for the
 * recorded latency behavior.
 *
 */

package org.LatencyUtils;