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A driver for DataStax Enterprise (DSE) and Apache Cassandra 1.2+ clusters that works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol, supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.

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/*
 * Copyright DataStax, Inc.
 *
 * This software can be used solely with DataStax Enterprise. Please consult the license at
 * http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
package com.datastax.driver.core;

/**
 * A {@code PercentileTracker} that maintains a separate histogram for each host.
 *
 * This gives you per-host latency percentiles, meaning that each host will only be compared to
 * itself.
 */
public class PerHostPercentileTracker extends PercentileTracker {
  private PerHostPercentileTracker(
      long highestTrackableLatencyMillis,
      int numberOfSignificantValueDigits,
      int minRecordedValues,
      long intervalMs) {
    super(
        highestTrackableLatencyMillis,
        numberOfSignificantValueDigits,
        minRecordedValues,
        intervalMs);
  }

  @Override
  protected Host computeKey(Host host, Statement statement, Exception exception) {
    return host;
  }

  /**
   * Returns a builder to create a new instance.
   *
   * @param highestTrackableLatencyMillis the highest expected latency. If a higher value is
   *     reported, it will be ignored and a warning will be logged. A good rule of thumb is to set
   *     it slightly higher than {@link SocketOptions#getReadTimeoutMillis()}.
   * @return the builder.
   */
  public static Builder builder(long highestTrackableLatencyMillis) {
    return new Builder(highestTrackableLatencyMillis);
  }

  /** Helper class to build {@code PerHostPercentileTracker} instances with a fluent interface. */
  public static class Builder extends PercentileTracker.Builder {

    Builder(long highestTrackableLatencyMillis) {
      super(highestTrackableLatencyMillis);
    }

    @Override
    protected Builder self() {
      return this;
    }

    @Override
    public PerHostPercentileTracker build() {
      return new PerHostPercentileTracker(
          highestTrackableLatencyMillis,
          numberOfSignificantValueDigits,
          minRecordedValues,
          intervalMs);
    }
  }
}