1.需求

选出前5条当前响应时间最大的url数据

2.实现

用key_id分组url，在内部选出最大taskFinishTime那条数据，根据其responseTime进行排序。

对buckets数据排序，要求排序字段是个值，不能是聚合。

所以这里使用scripted_metric统计last_response_time，就可以直接取到值。

（之前试过根据taskFinishTime排序，选出top hits 1的数据，显示其responseTime。但这种结果中有buckets，没法用作排序字段）

script中涉及：

taskFinishTime的是date类型的，取到的doc['taskFinishTime'].value不能直接和long类型的变量state.taskFinishTime作比较。

所以进行转换Date->Instant->Long，Date转Long语句doc['taskFinishTime'].value.toInstant().toEpochMilli()

es语句

GET /aaa/_search
{
  "size": 0,
  "query": {
    "bool": {
      "filter": {
        "range": {
          "taskFinishTime": {
            "gte": 1630825435000,
            "lte": 1630911835000
          }
        }
      },
      "must": [
        {
          "exists": {
            "field": "result.http_request.responseTime"
          }
        },
        {
          "exists": {
            "field": "result.http_request.statusCode"
          }
        }
      ]
    }
  },
  "aggs": {
    "group_by_url": {
      "terms": {
        "field": "key_id.keyword",
        "size": 10000
      },
      "aggs": {
        "url_nodealias": {
          "top_hits": {
            "size": 1,
            "_source": {
              "includes": [
                "nodealias"
              ]
            }
          }
        },
        "last_response_time": {
          "scripted_metric": {
            "init_script": "state.taskFinishTime = 0L; state.responseTime = 0L;",
            "map_script": "if(doc['taskFinishTime'].value.toInstant().toEpochMilli() > state.taskFinishTime) {state.taskFinishTime = doc['taskFinishTime'].value.toInstant().toEpochMilli(); state.responseTime = doc['result.http_request.responseTime'].value;}",
            "combine_script": "return state",
            "reduce_script": "long finalTaskFinishTime = 0L; double finalResponseTime = 0L; for (a in states){if(finalTaskFinishTime < a.taskFinishTime) {finalTaskFinishTime = a.taskFinishTime; finalResponseTime = a.responseTime;}} return finalResponseTime"
          }
        },
        "bucket_sort_temp": {
          "bucket_sort": {
            "sort": [
              {
                "last_response_time.value": {
                  "order": "desc"
                }
              }
            ],
            "size": 5
          }
        }
      }
    }
  }
}