Create java RestHighLevelClient in elastic cluster mode

问题

If elasticsearch runs on single mode, I can easily establish the RestHighLevel connection with this line of code:

RestHighLevelClient client = new RestHighLevelClient(
    RestClient.builder(
            new HttpHost("localhost", 9200, "http"),
            new HttpHost("localhost", 9201, "http")));

But if my elastic cluster has 3 machines, e.g., "host1", "host2", "host3", how to create the rest high level client in cluster mode ?

Thanks

回答1:

RestHighLevelClient client = new RestHighLevelClient(
        RestClient.builder(
                new HttpHost("host1", 9200, "http"),
                new HttpHost("host2", 9200, "http"),
                new HttpHost("host2", 9200, "http")
        )
);

As the doc it looks like you were referencing states, RestClient.builder accepts an array of HttpHosts to connect to. The client (which under the hood is the ES low-level REST client) will round-robin requests to these hosts. See also the Javadoc.

回答2:

As per the Elasticsearch docs you can pass multiple Elasticsearch hosts in RestClient.builder().

The better solution is to load the Elasticsearch hosts from configuration(application.conf in case of Scala-based application) instead of hardcoding it in the codebase.

Here is the Scala-based solution using Java Varargs(:_*).

application.conf

es_hosts = ["x.x.x.x","x.x.x.x","x.x.x.x"] // You can even use service-name/service-discovery
es_port = 9200
es_scheme = "http"

Code snippet

import collection.JavaConverters._
import com.typesafe.config.ConfigFactory
import org.apache.http.HttpHost
import org.elasticsearch.client.{RestClient, RestHighLevelClient}


val config = ConfigFactory.load()
val port = config.getInt(ES_PORT)
val scheme = config.getString(ES_SCHEME)

val es_hosts = config.getStringList(ES_HOSTS).asScala
val httpHosts = es_hosts.map(host => new HttpHost(host, port, scheme))

val low_level_client = RestClient.builder(httpHosts:_*)
val high_level_client: RestHighLevelClient = new RestHighLevelClient(low_level_client)

回答3:

To create High level REST client using multiple hosts, you can do something like following:

String[] esHosts = new String[]{"node1-example.com:9200", "node2-example.com:9200", 
    "node3-example.com:9200"};

final ClientConfiguration clientConfiguration = ClientConfiguration.builder()
    .connectedTo(esHosts)
    .build();

RestHighLevelClient restClient = RestClients.create(clientConfiguration).rest();

// Hostnames used for building client can be verified as following
List<Node> nodes = restClient.getLowLevelClient().getNodes();
nodes.forEach(node -> System.out.println(node.toString()));

References:

Docs for High Level REST Client
Source code for ClientConfigurationBuilder

来源：https://stackoverflow.com/questions/54975655/create-java-resthighlevelclient-in-elastic-cluster-mode

标签

ElasticSearch