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A Shaded CQL ActivityType driver for http://nosqlbench.io/

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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;

import java.util.concurrent.TimeUnit;

/**
 * A timestamp generator that guarantees monotonically increasing timestamps on a per-thread basis,
 * and logs warnings when timestamps drift in the future.
 *
 * Beware that there is a risk of timestamp collision with this generator when accessed by more
 * than one thread at a time; only use it when threads are not in direct competition for timestamp
 * ties (i.e., they are executing independent statements).
 *
 * @see AbstractMonotonicTimestampGenerator
 */
public class ThreadLocalMonotonicTimestampGenerator extends LoggingMonotonicTimestampGenerator {

  // We're deliberately avoiding an anonymous subclass with initialValue(), because this can
  // introduce
  // classloader leaks in managed environments like Tomcat
  private final ThreadLocal lastRef = new ThreadLocal();

  /**
   * Creates a new instance with a warning threshold and warning interval of one second.
   *
   * @see #ThreadLocalMonotonicTimestampGenerator(long, TimeUnit, long, TimeUnit)
   */
  public ThreadLocalMonotonicTimestampGenerator() {
    this(1, TimeUnit.SECONDS, 1, TimeUnit.SECONDS);
  }

  /**
   * Creates a new instance.
   *
   * @param warningThreshold how far in the future timestamps are allowed to drift before a warning
   *     is logged.
   * @param warningThresholdUnit the unit for {@code warningThreshold}.
   * @param warningInterval how often the warning will be logged if timestamps keep drifting above
   *     the threshold.
   * @param warningIntervalUnit the unit for {@code warningIntervalUnit}.
   */
  public ThreadLocalMonotonicTimestampGenerator(
      long warningThreshold,
      TimeUnit warningThresholdUnit,
      long warningInterval,
      TimeUnit warningIntervalUnit) {
    super(warningThreshold, warningThresholdUnit, warningInterval, warningIntervalUnit);
  }

  @Override
  public long next() {
    Long last = this.lastRef.get();
    if (last == null) last = 0L;

    long next = computeNext(last);

    this.lastRef.set(next);
    return next;
  }
}