Apache 未测量CouchDB响应时间统计信息

我有一个CouchDB实例在Windows服务器上运行。当我运行命令时：

curlhttp://HOSTNAME:5984/_node/_local/_stats/couchdb/request_time

我收到以下答复：

{
  "value": {
    "min": 0.0,
    "max": 0.0,
    "arithmetic_mean": 0.0,
    "geometric_mean": 0.0,
    "harmon ic_mean": 0.0,
    "median": 0.0,
    "variance": 0.0,
    "standard_deviation": 0.0,
    "skewness": 0.0,
    "kurtosis": 0.0,
    "percentile": [
      [
        50,
        0.0
      ],
      [
        75,
        0.0
      ],
      [
        90,
        0.0
      ],
      [
        95,
        0.0
      ],
      [
        99,
        0.0
      ],
      [
        999,
        0.0
      ]
    ],
    "histogram": [
      [
        0,
        0
      ]
    ],
    "n": 0
  },
  "type": "histogram",
  "desc": "length of a request inside CouchDB without MochiWeb"
}

我在这台服务器上有几个数据库，已经发出了大约50000个HTTP请求。为什么响应时间度量的所有值都等于零？如何激活此度量