无法从Spark连接到Cassandra(联系点包含多个数据中心)

Question

我正在尝试运行我的第一个spark作业（一个访问Cassandra的Scala作业），该作业失败并显示以下错误：

java.io.IOException: Failed to open native connection to Cassandra at {<ip>}:9042
at com.datastax.spark.connector.cql.CassandraConnector$.com$datastax$spark$connector$cql$CassandraConnector$$createSession(CassandraConnector.scala:164)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$2.apply(CassandraConnector.scala:150)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$2.apply(CassandraConnector.scala:150)
at com.datastax.spark.connector.cql.RefCountedCache.createNewValueAndKeys(RefCountedCache.scala:31)
...........
............
Caused by: java.lang.IllegalArgumentException: Contact points contain multiple data centers: 
at com.datastax.spark.connector.cql.LocalNodeFirstLoadBalancingPolicy.init(LocalNodeFirstLoadBalancingPolicy.scala:47)
at com.datastax.driver.core.Cluster$Manager.init(Cluster.java:1099)
at com.datastax.driver.core.Cluster.getMetadata(Cluster.java:271)
at com.datastax.spark.connector.cql.CassandraConnector$.com$datastax$spark$connector$cql$CassandraConnector$$createSession(CassandraConnector.scala:157)

我们在这里做错了什么？

我正在使用：

• Spark 1.5.2
• Apache Cassandra 2.1.10
• spark cassandra连接器1.3.1/1.5.0-M2（尝试了两个连接器）
• Scala版本2.10.4

Answer 1

-->据作者称，目前正在进行修复工作。请参阅此答案下方的评论。

我在文档中找到了这个，我希望它能帮助你：

override def init(cluster: Cluster, hosts: JCollection[Host]) {
    nodes = hosts.toSet
    // use explicitly set DC if available, otherwise see if all contact points have same DC
    // if so, use that DC; if not, throw an error
    dcToUse = localDC match { 
      case Some(local) => local
      case None => 
        val dcList = dcs(nodesInTheSameDC(contactPoints, hosts.toSet))
        if (dcList.size == 1) 
            dcList.head
        else 
            throw new IllegalArgumentException(s"Contact points contain multiple data centers: ${dcList.mkString(", ")}")
    }
    clusterMetadata = cluster.getMetadata
}

Answer 2

我在尝试使用Apache Spark 2.x.x连接两个Cassandra数据中心时遇到了同样的问题。

public class  SparkCassandraTest {  
  private static final String CASSANDRA_ENDPOINTS = "DC1_node1,DC1_node2,DC1_node3,DC2_node1,DC2_node2,DC2_node3";
  public static void main(String[] args) {
        sparkConf = new SparkConf().setAppName(APP_NAME);
        sparkConf.set("spark.cassandra.connection.host", CASSANDRA_ENDPOINTS);
        sparkConf.set("spark.cassandra.auth.username", CASSANDRA_USERNAME);
        sparkConf.set("spark.cassandra.auth.password", CASSANDRA_PASSWORD);
        sparkSession = SparkSession.builder().config(sparkConf).enableHiveSupport().getOrCreate();
        //.....................
        //.....................
        //.....................
       }
}

引起原因：java.lang.IollegalArgumentException：需求失败：联系点包含多个数据中心：DC2-XXXX2，DC1-XXXX1

我通过连接任意一个Cassandra数据中心（DC1_node1、DC2_node2和DC_node3）或（DC2_node1、DC2_node2C1_node3）来解决此问题。