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Elasticsearch Connector

Elasticsearch is a distributed, RESTful style search and data analysis engine. Apache Flink officially provides a connector for Elasticsearch, which is used to write data to Elasticsearch, which can provide at least once Semantics.

ElasticsearchSink uses TransportClient (before 6.x) or RestHighLevelClient (starting with 6.x) to communicate with the Elasticsearch cluster. Apache StreamPark further encapsulates Flink-connector-elasticsearch6, shields development details, and simplifies write operations for Elasticsearch6 and above.

hint

Because there are conflicts between different versions of Flink Connector Elasticsearch, StreamPark temporarily only supports write operations of Elasticsearch6 and above. If you wants to using Elasticsearch5, you need to exclude the flink-connector-elasticsearch6 dependency and introduce the flink-connector-elasticsearch5 dependency to create org.apache.flink.streaming.connectors.elasticsearch5.ElasticsearchSink instance writes data.

Dependency of elastic writing​

Different Elasticsearch versions rely on the Flink Connector Elasticsearch is not universal, the following information comes from the flink-docs-release-1.14 document:

Elasticsearch 5.x Maven dependencies


<dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-connector-elasticsearch5_2.11</artifactId>
    <version>1.14.3</version>
</dependency>

Elasticsearch 6.x Maven dependencies


<dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-connector-elasticsearch6_2.11</artifactId>
    <version>1.14.3</version>
</dependency>

Elasticsearch 7.x ans above Maven dependencies


<dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-connector-elasticsearch7_2.11</artifactId>
    <version>1.14.3</version>
</dependency>

Write data to Elasticsearch based on the official​

The following code is taken from the official documentationElasticsearch based on the official

import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.connectors.elasticsearch.ElasticsearchSinkFunction;
import org.apache.flink.streaming.connectors.elasticsearch.RequestIndexer;
import org.apache.flink.streaming.connectors.elasticsearch6.ElasticsearchSink;

import org.apache.http.HttpHost;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.client.Requests;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

DataStream<String> input=...;

        List<HttpHost> httpHosts=new ArrayList<>();
        httpHosts.add(new HttpHost("127.0.0.1",9200,"http"));
        httpHosts.add(new HttpHost("10.2.3.1",9200,"http"));

// 使用 ElasticsearchSink.Builder 创建 ElasticsearchSink
        ElasticsearchSink.Builder<String> esSinkBuilder=new ElasticsearchSink.Builder<>(
        httpHosts,
        new ElasticsearchSinkFunction<String>(){
public IndexRequest createIndexRequest(String element){
        Map<String, String> json=new HashMap<>();
        json.put("data",element);

        return Requests.indexRequest()
        .index("my-index")
        .type("my-type")
        .source(json);
        }

@Override
public void process(String element,RuntimeContext ctx,RequestIndexer indexer){
        indexer.add(createIndexRequest(element));
        }
        }
        );

// Configuration for batch requests; the settings below cause the sink to commit immediately after receiving each element that would otherwise be cached
        esSinkBuilder.setBulkFlushMaxActions(1);

A RestClientFactory that provides custom configuration information for internally created REST clients
        esSinkBuilder.setRestClientFactory(
        restClientBuilder->{
        restClientBuilder.setDefaultHeaders(...)
        restClientBuilder.setMaxRetryTimeoutMillis(...)
        restClientBuilder.setPathPrefix(...)
        restClientBuilder.setHttpClientConfigCallback(...)
        }
        );

// Finally, build and add the sink to the job pipeline
        input.addSink(esSinkBuilder.build());

The ElasticsearchSink created above is very inflexible to add parameters. StreamPark follows the concept of convention over configuration and automatic configuration. Users only need to configure es connection parameters and Flink operating parameters, and StreamPark will automatically assemble source and sink, which greatly simplifies development logic and improves development efficiency and maintainability.

Using Apache StreamPark™ writes to Elasticsearch​

Please ensure that operation requests are sent to the Elasticsearch cluster at least once after enabling Flink checkpointing in ESSink.

1. 配置策略和连接信息​

#redis sink configure
#  Required parameter, used by multiple nodes host1:port, host2:port,
host: localhost:9200
#  optional parameters
#  es:
#    disableFlushOnCheckpoint: true #默认为false
#    auth:
#    user:
#      password:
#    rest:
#      max.retry.timeout:
#      path.prefix:
#      content.type:
#    connect:
#      request.timeout:
#      timeout:
#    cluster.name: elasticsearch
#  client.transport.sniff:
#  bulk.flush.:

2. 写入Elasticsearch​

Using StreamPark writes to Elasticsearch

import org.apache.streampark.flink.core.scala.FlinkStreaming
import org.apache.streampark.flink.core.scala.sink.ESSink
import org.apache.streampark.flink.core.scala.util.ElasticSearchUtils
import org.apache.flink.api.scala._
import org.elasticsearch.action.index.IndexRequest
import org.json4s.DefaultFormats
import org.json4s.jackson.Serialization

import java.util.Date

object ConnectorApp extends FlinkStreaming {


  implicit lazy val formats: DefaultFormats.type = org.json4s.DefaultFormats

  override def handle(): Unit = {
    val ds = context.fromCollection(List(
      OrderEntity(1, 1, 11.3d, 3.1d, new Date()),
      OrderEntity(2, 1, 12.3d, 3.2d, new Date()),
      OrderEntity(3, 1, 13.3d, 3.3d, new Date()),
      OrderEntity(4, 1, 14.3d, 3.4d, new Date()),
      OrderEntity(5, 1, 15.3d, 7.5d, new Date()),
      OrderEntity(6, 1, 16.3d, 3.6d, new Date()),
      OrderEntity(7, 1, 17.3d, 3.7d, new Date())
    ))

    // es sink.........

    //1)Define the writing rules for Index
    implicit def indexReq(x: OrderEntity): IndexRequest = ElasticSearchUtils.indexRequest(
      "flink_order",
      "_doc",
      s"${x.id}_${x.time.getTime}",
      Serialization.write(x)
    )
    //3)define esSink and sink = data. done
    ESSink().sink6[OrderEntity](ds)
  }


  case class OrderEntity(id: Int, num: Int, price: Double, gmv: Double, time: Date) extends Serializable

}

Flink ElasticsearchSinkFunction可以执行多种类型请求，如（DeleteRequest、 UpdateRequest、IndexRequest）,StreamPark也对以上功能进行了支持，对应方法如下：

import org.apache.streampark.flink.core.scala.StreamingContext
import org.apache.flink.streaming.api.datastream.DataStreamSink
import org.apache.flink.streaming.api.scala.DataStream
import org.apache.flink.streaming.connectors.elasticsearch.ActionRequestFailureHandler
import org.apache.flink.streaming.connectors.elasticsearch.util.RetryRejectedExecutionFailureHandler
import org.apache.flink.streaming.connectors.elasticsearch6.RestClientFactory
import org.elasticsearch.action.delete.DeleteRequest
import org.elasticsearch.action.index.IndexRequest
import org.elasticsearch.action.update.UpdateRequest

import java.util.Properties
import scala.annotation.meta.param


class ESSink(@(transient@param) context: StreamingContext,
             property: Properties = new Properties(),
             parallelism: Int = 0,
             name: String = null,
             uid: String = null) {

  /**
   * for ElasticSearch6
   *
   * @param stream
   * @param suffix
   * @param restClientFactory
   * @param failureHandler
   * @param f
   * @tparam T
   * @return
   */
  def sink6[T](stream: DataStream[T],
               suffix: String = "",
               restClientFactory: RestClientFactory = null,
               failureHandler: ActionRequestFailureHandler = new RetryRejectedExecutionFailureHandler)
              (implicit f: T => IndexRequest): DataStreamSink[T] = {

    new ES6Sink(context, property, parallelism, name, uid).sink[T](stream, suffix, restClientFactory, failureHandler, f)
  }


  def update6[T](stream: DataStream[T],
                 suffix: String = "",
                 restClientFactory: RestClientFactory = null,
                 failureHandler: ActionRequestFailureHandler = new RetryRejectedExecutionFailureHandler)
                (f: T => UpdateRequest): DataStreamSink[T] = {

    new ES6Sink(context, property, parallelism, name, uid).sink[T](stream, suffix, restClientFactory, failureHandler, f)
  }


  def delete6[T](stream: DataStream[T],
                 suffix: String = "",
                 restClientFactory: RestClientFactory = null,
                 failureHandler: ActionRequestFailureHandler = new RetryRejectedExecutionFailureHandler)
                (f: T => DeleteRequest): DataStreamSink[T] = {

    new ES6Sink(context, property, parallelism, name, uid).sink[T](stream, suffix, restClientFactory, failureHandler, f)
  }

}
info

When the Flink checkpoint is enabled, the Flink Elasticsearch Sink guarantees that operation requests are sent to the Elasticsearch cluster at least once. It does this by waiting for all pending operation requests in the BulkProcessor while checkpointing. This effectively guarantees that all requests will be successfully acknowledged by Elasticsearch before triggering the checkpoint and proceeding to process records sent to the sink. If the user wants to disable flushing, they can configure disableFlushOnCheckpoint to true to do so, which essentially means that the sink will no longer provide any reliable delivery guarantees, even if checkpointing of the job topology is enabled.

Other configuration​

deal with failed Elasticsearch request​

An Elasticsearch operation request may fail for a variety of reasons. You can specify the failure handling logic by implementing ActionRequestFailureHandler. See Official Documentation - Handling Failed Elasticsearch Requests

Configure the internal batch processor​

The BulkProcessor inside es can further configure its behavior of how to refresh the cache operation request, see the official documentation for details - Configuring the Internal Bulk Processor

Apache StreamPark™ configuration​

All other configurations must comply with the StreamPark configuration. For specific configurable items and the role of each parameter, please refer to the project configuration