append(buf, "percent", () -> osProbe.getSystemCpuPercent());
        final OsStats osStats = osProbe.osStats();
        buf.append("},");
        append(buf, "load_averages", () -> osStats.getCpu().getLoadAverage());
        buf.append("},");
    }

    private void appendFesenStats(final StringBuilder buf) {
        String stats = null;
        try {

     */
    // GET /api/admin/stats
    @Execute
    public JsonResponse<ApiResult> index() {
        final HashMap<String, Object> stats = new HashMap<>();
        stats.put("jvm", getJvmObj());
        stats.put("os", getOsObj());
        stats.put("process", getProcessObj());
        stats.put("engine", getEngineObj());
        stats.put("fs", getFsObj());

   *
   * <ul>
   *   <li>Both {@code xStats} and {@code yStats} must have the same {@code count}.
   *   <li>If that {@code count} is 1, {@code sumOfProductsOfDeltas} must be exactly 0.0.
   *   <li>If that {@code count} is more than 1, {@code sumOfProductsOfDeltas} must be finite.
   * </ul>
   */
  PairedStats(Stats xStats, Stats yStats, double sumOfProductsOfDeltas) {
    this.xStats = xStats;
    this.yStats = yStats;

   * versions.
   */
  public static Stats fromByteArray(byte[] byteArray) {
    checkNotNull(byteArray);
    checkArgument(
        byteArray.length == BYTES,
        "Expected Stats.BYTES = %s remaining , got %s",
        BYTES,
        byteArray.length);
    return readFrom(ByteBuffer.wrap(byteArray).order(ByteOrder.LITTLE_ENDIAN));
  }

  /**

              + (values.xStats().mean() - xStats.mean())
                  * (values.yStats().mean() - yStats.mean())
                  * values.count();
    }
    yStats.addAll(values.yStats());
  }

  /** Returns an immutable snapshot of the current statistics. */
  public PairedStats snapshot() {
    return new PairedStats(xStats.snapshot(), yStats.snapshot(), sumOfProductsOfDeltas);
  }

    assertStatsApproxEqual(EMPTY_STATS_ITERABLE, emptyAccumulatorByAddAllEmptyPairedStats.xStats());
    assertStatsApproxEqual(ONE_VALUE_STATS, oneValueAccumulator.xStats());
    assertStatsApproxEqual(ONE_VALUE_STATS, oneValueAccumulatorByAddAllEmptyPairedStats.xStats());
    assertStatsApproxEqual(TWO_VALUES_STATS, twoValuesAccumulator.xStats());
    assertStatsApproxEqual(

    assertEquals(2, stats.requestCount());
    assertEquals(1, stats.hitCount());
    assertThat(stats.hitRate()).isEqualTo(1.0 / 2);
    assertEquals(1, stats.missCount());
    assertThat(stats.missRate()).isEqualTo(1.0 / 2);
    assertEquals(1, stats.loadCount());
    assertEquals(0, stats.evictionCount());

    Object two = new Object();
    cache.getUnchecked(two);
    stats = cache.stats();
    assertEquals(3, stats.requestCount());

    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(0, stats.hitCount());

    assertSame(key, cache.get(key));
    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());

    StatsCounter counter = new SimpleStatsCounter();
    CacheStats stats = counter.snapshot();
    assertEquals(0, stats.requestCount());
    assertEquals(0, stats.hitCount());
    assertThat(stats.hitRate()).isEqualTo(1.0);
    assertEquals(0, stats.missCount());
    assertThat(stats.missRate()).isEqualTo(0.0);
    assertEquals(0, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(0, stats.loadCount());

        // this getUnchecked() call shouldn't be a cache miss; verified below
        assertEquals(entry.getValue(), cache.getUnchecked(entry.getKey()));
      }
      assertEquals(WARMUP_SIZE, cache.stats().missCount());
      checkValidState(cache);
    }
  }

  public void testPut_populated() {
    for (LoadingCache<Object, Object> cache : caches()) {
      // don't let the entries get GCed