date {
      match => ["start_time","ISO8601"]
    }

但實際發現每個document都會附帶一個[_dataparserfail]的標簽，百思不得姐
google一番後終於明白了，鏈接：https://discuss.elastic.co/t/trouble-matching-timestamp/83768/4

因為從mysql取到數據的時候start_time 已經是一個時間的數據類型了， 這時候再用date去處理自然失敗，如果想使用這個字段作為@timestamp ，老外給的解決方法如下：
In your SQL query, typecast the timestamp as a string.
Use a mutate filter‘s convert option to typecast the field to a string prior to the date filter.
Use a mutate filter to copy the timestamp into @timestamp and overwrite the existing value (use the replace option).

我使用的方法：

    mutate {
      add_field => {"temp_ts" => "%{start_time}"}
    }
    date {
      match => ["temp_ts","ISO8601"]
      remove_field => ["temp_ts"]
    }

logstash-input-jdbc取mysql數據日期格式處理