参照官网链接

https://www.elastic.co/guide/en/elasticsearch/reference/6.4/accessing-data-in-pipelines.html#accessing-ingest-metadata

创建摄取管道：

PUT _ingest/pipeline/set_timestamp
{
  "description": "adds the timestamp when a document is indexed",
  "processors": [
    {
      "set": {
        "field": "indexed_at",
        "value": "{
  {_ingest.timestamp}}"
      }
    }
  ]
} 

更新文档，并引用管道：

PUT tmp/_doc/1?pipeline=set_timestamp
{
  "test": "foo"
}

查询文档，会发现多一个字段：

GET tmp/_doc/1
{
  "test" : "foo",
  "indexed_at" : "2019-10-03T13:19:03.181Z"
}