學習用Node.js和Elasticsearch構建搜索引擎（7）：零停機時間更新索引配置或遷移索引

上一篇說到若是一個索引的mapping設置過了，想要修改type或analyzer，一般的作法是新建一個索引，從新設置mapping，再把數據同步過來。

那麼如何實現零停機時間更新索引配置或遷移索引？這就須要用到索引的別名設置。

思路：

一、假設咱們的索引是demo_v1，咱們定義了一個別名demo，之後全部的操做都用別名demo操做。

二、如今索引demo_v1的mapping設置或者其餘一些設置不知足咱們的需求了，咱們須要修改。新建一個索引demo_v2，同時設置好最新配置。

三、同步索引demo_v1的數據到索引demo_v2。直到同步完。

四、移除索引demo_v1的別名demo，同時設置索引demo_v2的別名爲demo。

五、刪除索引demo_v1。

六、遷移完成。之後若是還有設置變動，能夠按照這個思路繼續設置索引demo_v三、demo_v4……

 

接下來用一個例子說明實現過程，實際項目中我也是按這個思路作的。若是有一些命令操做看不懂，可參看上一篇文章。

一、建立索引demo_v1

> curl -XPUT 'localhost:9200/demo_v1'  
{"acknowledged":true,"shards_acknowledged":true}%

二、給索引demo_v1添加幾條數據

#給索引demo_v1添加了type=fruit的3條數據，每條數據用name和tag兩個字段
> curl -XPOST 'localhost:9200/_bulk?pretty' -d'
{ "index" : { "_index" : "demo_v1", "_type" : "fruit", "_id" : "1" }}
{ "name" : "蘋果","tag":"蘋果,水果,紅富士"}
{ "create" : { "_index" : "demo_v1", "_type" : "fruit", "_id" : "2" }}
{ "name" : "香蕉","tag":"香蕉,水果,海南,彎彎,小黃人"}
{ "index" : { "_index" : "demo_v1", "_type" : "fruit", "_id" : "3" }}
{ "name" : "西瓜","tag":"西瓜,水果,圓形,綠,閏土"}
'
#返回 {
  "took" : 34,
  "errors" : false,
  "items" : [
    {
      "index" : {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "1",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "created" : true,
        "status" : 201
      }
    },
    {
      "create" : {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "2",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "created" : true,
        "status" : 201
      }
    },
    {
      "index" : {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "3",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "created" : true,
        "status" : 201
      }
    }
  ]
}

三、給索引demo_v1設置別名demo

#設置別名
> curl -XPUT 'localhost:9200/demo_v1/_alias/demo'
{"acknowledged":true}%

四、使用別名查看信息

#使用別名查看一下數據，是能夠查詢到的
> curl -XGET 'localhost:9200/demo/fruit/_search?pretty' #查看mapping
> curl -XGET 'localhost:9200/demo/fruit/_mapping?pretty' #返回
{
  "demo_v1" : {
    "mappings" : {
      "fruit" : {
        "properties" : {
          "name" : {
            "type" : "text",
            "fields" : {
              "keyword" : {
                "type" : "keyword",
                "ignore_above" : 256
              }
            }
          },
          "tag" : {
            "type" : "text",
            "fields" : {
              "keyword" : {
                "type" : "keyword",
                "ignore_above" : 256
              }
            }
          }
        }
      }
    }
  }
}

#檢索數據
> curl -XGET 'http://localhost:9200/demo/fruit/_search?pretty' -d '{
    "query" : {
        "term" : { "tag" : "水" }
   }
}'
#返回
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : 0.28582606,
    "hits" : [
      {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "1",
        "_score" : 0.28582606,
        "_source" : {
          "name" : "蘋果",
          "tag" : "蘋果,水果,紅富士"
        }
      },
      {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "3",
        "_score" : 0.27233246,
        "_source" : {
          "name" : "西瓜",
          "tag" : "西瓜,水果,圓形,綠,閏土"
        }
      },
      {
        "_index" : "demo_v1",
        "_type" : "fruit",
        "_id" : "2",
        "_score" : 0.24257512,
        "_source" : {
          "name" : "香蕉",
          "tag" : "香蕉,水果,海南,彎彎,小黃人"
        }
      }
    ]
  }
}

數據由於先前建立索引時沒有設置mapping，因此這些設置都是默認設置，分詞器也默認標準分詞器。

上面檢索標籤tag中帶有「水」的數據，都查詢出來了，說明默認分詞器把「水果」這個詞拆分了。

若是咱們須要tag字段按照逗號分詞，「水果」做爲一個完整的詞不拆分該怎麼弄呢？

五、新建一個索引demo_v2，同時自定義逗號分詞器，並把逗號分詞器應用到tag字段上

#新建索引demo_v2
> curl -XPUT 'http://localhost:9200/demo_v2/' -d'{
  "settings": {
    "index": {
      "analysis": {
        "analyzer": {
          "douhao_analyzer": {
            "pattern": ",",
            "type": "pattern"
          }
        }
      },
      "number_of_shards": 5,
      "number_of_replicas": 1
    }
  },
  "mappings": {
    "fruit": {
      "properties": {
        "name": {
          "type": "text",
          "index": "not_analyzed"
        },
        "tag": {
          "type": "string",
          "analyzer": "douhao_analyzer",
          "search_analyzer": "douhao_analyzer"
        }
      }
    }
  }
}'
#返回 {"acknowledged":true,"shards_acknowledged":true}%

 關於mapping設置及分詞器設置可參見官方文檔：

 https://www.elastic.co/guide/en/elasticsearch/reference/5.3/mapping.html#mapping-type

 https://www.elastic.co/guide/en/elasticsearch/reference/5.3/analysis-analyzers.html

六、同步索引demo_v1中的數據到demo_v2

我使用工具elasticdump同步數據，ElasticDump是一個ElasticSearch的數據導入導出開源工具包。

官方地址：https://github.com/taskrabbit/elasticsearch-dump

同步命令以下：

> elasticdump --input='http://localhost:9200/demo_v1'  --output='http://localhost:9200/demo_v2' --type=data
Wed, 21 Jun 2017 09:53:15 GMT | starting dump
Wed, 21 Jun 2017 09:53:15 GMT | got 3 objects from source elasticsearch (offset: 0)
Wed, 21 Jun 2017 09:53:15 GMT | sent 3 objects to destination elasticsearch, wrote 3
Wed, 21 Jun 2017 09:53:15 GMT | got 0 objects from source elasticsearch (offset: 3)
Wed, 21 Jun 2017 09:53:15 GMT | Total Writes: 3
Wed, 21 Jun 2017 09:53:15 GMT | dump complete

七、驗證一下demo_v2中的數據

#檢索tag中包含「水」的數據，檢索不到就是正常的
curl -XGET 'http://localhost:9200/demo_v2/fruit/_search?pretty' -d '{
    "query" : {
        "term" : { "tag" : "水" }
   }
}'
 #檢索tag中包含「水果」的數據，能夠所有檢索到
curl -XGET 'http://localhost:9200/demo_v2/fruit/_search?pretty' -d '{
    "query" : {
        "term" : { "tag" : "水果" }
   }
}'

八、移除索引demo_v1的別名demo，同時設置索引demo_v2的別名爲demo

curl -XPOST 'localhost:9200/_aliases?pretty' -d'{
  "actions" : [
  { "remove" : { "index" : "demo_v1", "alias" : "demo" } },
  { "add" : { "index" : "demo_v2", "alias" : "demo" } }
]}'

九、刪除索引demo_v1

curl -XDELETE 'localhost:9200/demo_v1'

至此整個遷移完成

ok!