routing路由

1.routing路由

ES在添加数据时，会根据id或者routing参数进行hash，得到hash值再与该索引库的分片数量取模，得到的值即为存入的分片编号。如果多条数据使用相同的routing，那么最终计算出来的分片编号都是一样的，那么这些数据就可以存储到相同的分片里面了。后期查询的只需要到指定分片中查询即可，可以显著提高查询性能。

如果在面试的时候面试官问你如何在ES中实现极速查询，其实就是问这个routing路由功能。

下面来演示一下： 创建一个新的索引库，指定5个分片，0个副本。

curl -H "Content-Type: application/json" -XPUT 'http://master:9200/rout/' -d'{"settings":{"number_of_shards":5,"number_of_replicas":0}}'

初始化数据：

curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/1?routing=class1' -d'{"name":"tom","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/2?routing=class1' -d'{"name":"jack","age":29}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/3?routing=class1' -d'{"name":"jessica","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/4?routing=class1' -d'{"name":"dave","age":19}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/5?routing=class1' -d'{"name":"lilei","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/6?routing=class1' -d'{"name":"lili","age":29}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/7?routing=class1' -d'{"name":"simoni","age":28}'
curl -H "Content-Type: application/json" -XPOST 'http://master:9200/rout/_doc/7?routing=class1' -d'{"name":"anthony","age":22}'

如果是使用的JavaAPI，那么需要通过使用routing函数指定。

private static void addIndexByJson(RestHighLevelClient client) throws IOException {
    IndexRequest request = new IndexRequest("emp");
    request.id("10");
    String jsonString = "{" +
            "\"name\":\"jessic\"," +
            "\"age\":20" +
            "}";
    request.source(jsonString, XContentType.JSON);
    request.routing("class1");
    //执行
    client.index(request, RequestOptions.DEFAULT);
}

查看数据在分片中的分布情况，发现所有数据都在0号分片里面，说明routing参数生效了。

java代码实现：

package com.simoniu.db_elasticsearch.routing;
import org.apache.http.HttpHost;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;


/**
 * 偏好查询(分片查询方式)
 * Created by simoniu
 */
public class EsRoutingDemo {
    public static void main(String[] args) throws Exception{
        //获取RestClient连接
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(
                        new HttpHost("master",9200,"http"),
                        new HttpHost("slave1",9200,"http"),
                        new HttpHost("slave2",9200,"http")));
        SearchRequest searchRequest = new SearchRequest();
        searchRequest.indices("pre");


        searchRequest.indices("rout");
        //指定分片查询方式
        /*
       通过偏好查询中的_shard手工指定分片编号在使用的时候不太友好，需要我们单独维护一份数据和分片之间的关系，比较麻烦。
       还有一种比较简单常用的方式是在查询的时候设置相同的路由参数，这样就可以快速查询到使用这个路由参数添加的数据了。
       底层其实是会计算这个路由参数对应的分片编号，最终到指定的分片中查询数据。*/
        //searchRequest.preference("_shards:0");
        //指定路由参数
        searchRequest.routing("class1");

        //我们把routing参数修改一下，改为class2
        //searchRequest.routing("class2");
        //执行查询操作
        SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

        //获取查询返回的结果
        SearchHits hits = searchResponse.getHits();
        //获取数据总量
        long numHits = hits.getTotalHits().value;
        System.out.println("数据总数："+numHits);
        //获取具体内容
        SearchHit[] searchHits = hits.getHits();
        //迭代解析具体内容
        for (SearchHit hit : searchHits) {
            String sourceAsString = hit.getSourceAsString();
            System.out.println(sourceAsString);
        }

        //关闭连接
        client.close();
    }
}

运行结果：

数据总数：8
{"name":"tom","age":18}
{"name":"jack","age":29}
{"name":"jessica","age":18}
{"name":"dave","age":19}
{"name":"lilei","age":18}
{"name":"lili","age":29}
{"name":"simoni","age":28}
{"name":"anthony","age":22}