ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertThat(map.containsKey(key)).isTrue();
    assertThat(segment.accessQueue.peek()).isSameInstanceAs(entry);
    assertThat(segment.accessQueue).hasSize(1);

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertThat(map.containsKey(key)).isTrue();
    assertThat(segment.accessQueue.peek()).isSameInstanceAs(entry);
    assertThat(segment.accessQueue).hasSize(1);

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());

    assertThat(cache.apply(7)).isEqualTo(6);
  }

  @Test
  public void expireAfterAccess() {
    Cache<Integer, Integer> cache =
        CacheBuilder.newBuilder().expireAfterAccess(1000, MILLISECONDS).ticker(fakeTicker).build();

    cache.put(0, 10);
    cache.put(2, 30);

    fakeTicker.advance(999, MILLISECONDS);
    assertThat(cache.getIfPresent(2)).isEqualTo(30);
    fakeTicker.advance(1, MILLISECONDS);

            return immediateFuture(two);
          }
        };

    LoadingCache<Object, Object> cache =
        CacheBuilder.newBuilder()
            .recordStats()
            .ticker(ticker)
            .refreshAfterWrite(1, MILLISECONDS)
            .build(loader);
    Object key = new Object();
    CacheStats stats = cache.stats();
    assertThat(stats.missCount()).isEqualTo(0);

    assertThat(cache.apply(7)).isEqualTo(6);
  }

  @Test
  public void expireAfterAccess() {
    Cache<Integer, Integer> cache =
        CacheBuilder.newBuilder().expireAfterAccess(1000, MILLISECONDS).ticker(fakeTicker).build();

    cache.put(0, 10);
    cache.put(2, 30);

    fakeTicker.advance(999, MILLISECONDS);
    assertThat(cache.getIfPresent(2)).isEqualTo(30);
    fakeTicker.advance(1, MILLISECONDS);

  static final class Timestamped<V> {
    private final V value;
    private final Ticker ticker;
    private long writeTimestamp;
    private long accessTimestamp;

    Timestamped(V value, Ticker ticker) {
      this.value = checkNotNull(value);
      this.ticker = checkNotNull(ticker);
      this.writeTimestamp = ticker.read();
      this.accessTimestamp = this.writeTimestamp;
    }

    V getValue() {

   * @throws IllegalStateException if a ticker was already set
   */
  @CanIgnoreReturnValue
  public CacheBuilder<K, V> ticker(Ticker ticker) {
    checkState(this.ticker == null);
    this.ticker = checkNotNull(ticker);
    return this;
  }

  Ticker getTicker(boolean recordsTime) {
    if (ticker != null) {
      return ticker;
    }
    return recordsTime ? Ticker.systemTicker() : NULL_TICKER;
  }

  }

  public void testElapsed_notRunning() {
    ticker.advance(1);
    stopwatch.start();
    ticker.advance(4);
    stopwatch.stop();
    ticker.advance(9);
    assertEquals(4, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_multipleSegments() {
    stopwatch.start();
    ticker.advance(9);
    stopwatch.stop();

    ticker.advance(16);

    stopwatch.start();

		},
		{
			val:   0.79,
			label: labels[2],
		},
	}
	ticker := time.NewTicker(1 * time.Millisecond)
	defer ticker.Stop()
	for _, obs := range observations {
		// Send observations once every 1ms, to simulate delay between
		// observations. This is to test the channel based
		// synchronization used internally.
		<-ticker.C
		ttfbHist.With(prometheus.Labels{"api": obs.label}).Observe(obs.val)
	}

            return immediateFuture(two);
          }
        };

    LoadingCache<Object, Object> cache =
        CacheBuilder.newBuilder()
            .recordStats()
            .ticker(ticker)
            .refreshAfterWrite(1, MILLISECONDS)
            .build(loader);
    Object key = new Object();
    CacheStats stats = cache.stats();
    assertThat(stats.missCount()).isEqualTo(0);