resync(nowMicros);
    double stableIntervalMicros = SECONDS.toMicros(1L) / permitsPerSecond;
    this.stableIntervalMicros = stableIntervalMicros;
    doSetRate(permitsPerSecond, stableIntervalMicros);
  }

  abstract void doSetRate(double permitsPerSecond, double stableIntervalMicros);

  @Override
  final double doGetRate() {
    return SECONDS.toMicros(1L) / stableIntervalMicros;
  }

  @Override

    long instant = 0L;
    final List<String> events = Lists.newArrayList();

    @Override
    public long readMicros() {
      return NANOSECONDS.toMicros(instant);
    }

    void sleepMillis(int millis) {
      sleepMicros("U", MILLISECONDS.toMicros(millis));
    }

    void sleepMicros(String caption, long micros) {
      instant += MICROSECONDS.toNanos(micros);

   */
  @CanIgnoreReturnValue
  public double acquire(int permits) {
    long microsToWait = reserve(permits);
    stopwatch.sleepMicrosUninterruptibly(microsToWait);
    return 1.0 * microsToWait / SECONDS.toMicros(1L);
  }

  /**
   * Reserves the given number of permits from this {@code RateLimiter} for future use, returning
   * the number of microseconds until the reservation can be consumed.
   *

    long instant = 0L;
    final List<String> events = Lists.newArrayList();

    @Override
    public long readMicros() {
      return NANOSECONDS.toMicros(instant);
    }

    void sleepMillis(int millis) {
      sleepMicros("U", MILLISECONDS.toMicros(millis));
    }

    void sleepMicros(String caption, long micros) {
      instant += MICROSECONDS.toNanos(micros);