ElasticSearch7.3学习(十四)—-生产环境实时重建索引

1、实时重建索引

在实际的生产环境中,一个field的设置是不能被修改的,如果要修改一个Field,那么应该重新按照新的mapping,建立一个index,然后将数据批量查询出来,重新用bulk api写入index中。

批量查询的时候,建议采用scroll api,并且采用多线程并发的方式来reindex数据。例如说每次scoll就查询指定日期的一段数据,交给一个线程即可。

(1) 一开始,依靠dynamic mapping,插入数据,但是不小心有些数据是2019-09-10这种日期格式的,所以title这种field被自动映射为了date类型,实际上它应该是string类型的。

首先插入以下数据

PUT /my_index/_doc/1
{
  "title": "2019-09-10"
}

PUT /my_index/_doc/2
{
  "title": "2019-09-11"
}

(2)当后期向索引中加入string类型的title值的时候,就会报错

PUT /my_index/_doc/3
{
  "title": "my first article"
}

报错

{
  "error": {
    "root_cause": [
      {
        "type": "mapper_parsing_exception",
        "reason": "failed to parse field [title] of type [date] in document with id '3'. Preview of field's value: 'my first article'"
      }
    ],
    "type": "mapper_parsing_exception",
    "reason": "failed to parse field [title] of type [date] in document with id '3'. Preview of field's value: 'my first article'",
    "caused_by": {
      "type": "illegal_argument_exception",
      "reason": "failed to parse date field [my first article] with format [strict_date_optional_time||epoch_millis]",
      "caused_by": {
        "type": "date_time_parse_exception",
        "reason": "Failed to parse with all enclosed parsers"
      }
    }
  },
  "status": 400
}

(3)如果此时想修改title的类型,是不可能的

PUT /my_index/_mapping
{
  "properties": {
    "title": {
      "type": "text"
   	}
  }
}

报错

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "mapper [title] of different type, current_type [date], merged_type [text]"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "mapper [title] of different type, current_type [date], merged_type [text]"
  },
  "status": 400
}

(4)此时,唯一的办法,就是进行reindex,也就是说,重新建立一个索引,将旧索引的数据查询出来,再导入新索引。

(5)如果说旧索引的名字,是old_index,新索引的名字是new_index,终端java应用,已经在使用old_index在操作了,难道还要去停止java应用,修改使用的indexnew_index,才重新启动java应用吗?这个过程中,就会导致java应用停机,可用性降低。

(6)所以说,给java应用一个别名,这个别名是指向旧索引的,java应用先用着,java应用先用prod_index来操作,此时实际指向的是旧的my_index

PUT /my_index/_alias/prod_index

(7)查看别名,会发现my_index已经存在一个别名prod_index了。

GET my_index/_alias

(8)新建一个index,调整其title的类型为string

PUT /my_index_new
{
  "mappings": {
    "properties": {
      "title": {
        "type": "text"
      }
    }
  }
}

(9)使用scroll api将数据批量查询出来

GET /my_index/_search?scroll=1m
{
  "query": {
    "match_all": {}
  },
  "size": 1
}

返回

{
  "_scroll_id" : "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAARUMWQWx5bzRmTW9TeUNpNmVvN0E2dF9YQQ==",
  "took" : 4,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "title" : "2019-09-10"
        }
      }
    ]
  }
}

(9)采用bulk apiscoll查出来的一批数据,批量写入新索引

POST /_bulk
{"index":{"_index":"my_index_new","_id":"1"}}
{"title":"2019-09-10"}

(10)反复循环8~9,查询一批又一批的数据出来,采取bulk api将每一批数据批量写入新索引

(11)将my_index索引的别名prod_index切换到my_index_new上去,java应用会直接通过index别名使用新的索引中的数据,java应用程序不需要停机,零提交,高可用

POST /_aliases
{
  "actions": [
    {
      "remove": {
        "index": "my_index",
        "alias": "prod_index"
      }
    },
    {
      "add": {
        "index": "my_index_new",
        "alias": "prod_index"
      }
    }
  ]
}

(12)直接通过prod_index别名来查询,是否ok

GET prod_index/_search

可以看到能够查询到新索引my_index_new的数据了

{
  "took" : 1117,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "my_index_new",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "title" : "2019-09-10"
        }
      }
    ]
  }
}

2、总结:

基于aliasclient透明切换index

PUT /my_index_v1/_alias/my_index

clientmy_index进行操作

reindex操作,完成之后,切换v1到v2

POST /_aliases
{
    "actions": [
        { "remove": { "index": "my_index_v1", "alias": "my_index" }},
        { "add":    { "index": "my_index_v2", "alias": "my_index" }}
    ]
}

 

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