一，ingest节点的作用

ingest节点在稳定写入前对文档进行指定的预处理，类似大数据的ETL

二，ingest的使用

默认集群每个节点都具有ingest的作用，通常建议配置具有单一职责的ingest节点。

确定ingest节点后，要定义pipeline，pipeline中指定具体的逻辑。

三，ingest的使用总结

1，定义pipeline

PUT _ingest/pipeline/indexed_at
{
  "processors": [
    {
      "script": {
        "source": "ctx.indexed_at = new Date()"
      }
    }
  ]
}

PUT _ingest/pipeline/update_pipeline
{
  "processors": [
    {
      "script": {
        "source": """
           if(ctx.indexed_at != null) {
             ctx.indexed_at2 = new Date()
           }
        """
      }
    }
  ]
}

PUT _ingest/pipeline/reindex_ingest
{
  "processors": [
    {
      "script": {
        "source": """
           ctx.index = new Random().nextInt()
        """
      }
    }
  ]
}

2，使用方式

• 定义索引时指定pipeline

PUT index_ingest
{
  "settings": {
    "index.default_pipeline": "indexed_at"
  }
}

• 写入文档时指定pipeline

POST /index_ingest/_doc/1?pipeline=indexed_at
{
  "content":"ingest test"
}

• update时使用pipeline

POST index_ingest/_update_by_query?pipeline=update_pipeline
{
  "query": {
    "match_all": {}
  }
}

• reindex时使用pipeline

POST _reindex
{
  "source": {
    "index": "index_ingest"
  },
  "dest": {
    "index": "index_ingest_new",
    "pipeline": "reindex_ingest"
  }
}