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/*
 * Copyright DataStax, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.datastax.driver.core;

/**
 * A {@code PercentileTracker} that aggregates all measurements into a single histogram.
 *
 * This gives you global latency percentiles for the whole cluster, meaning that latencies of
 * slower hosts will tend to appear in higher percentiles.
 */
public class ClusterWidePercentileTracker extends PercentileTracker {
  private volatile Cluster cluster;

  private ClusterWidePercentileTracker(
      long highestTrackableLatencyMillis,
      int numberOfSignificantValueDigits,
      int minRecordedValues,
      long intervalMs) {
    super(
        highestTrackableLatencyMillis,
        numberOfSignificantValueDigits,
        minRecordedValues,
        intervalMs);
  }

  @Override
  public void onRegister(Cluster cluster) {
    this.cluster = cluster;
  }

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

  /**
   * 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 ClusterWidePercentileTracker build() {
      return new ClusterWidePercentileTracker(
          highestTrackableLatencyMillis,
          numberOfSignificantValueDigits,
          minRecordedValues,
          intervalMs);
    }
  }
}