Unable to connect Spark to Cassandra DB in RStudio

问题

I've spent the last week trying to figure out how to use sparlyr to get spark to connect to cassandra on our local cluster, and I've hit a wall - any help would be greatly appreciated. I'm the only one trying to use R/Rstudio to make this connection (everyone else uses Java on NetBeans and Maven), and am not sure what I need to do to make this work.

The stack I'm using is: Ubuntu 16.04 (in a VM) sparklyr: 0.5.3 Spark: 2.0.0 Scala: 2.11 Cassandra: 3.7

relevant config.yml file settings:

# cassandra settings
spark.cassandra.connection.host: <cluster_address>
spark.cassandra.auth.username: <user_name>
spark.cassandra.auth.password: <password>

sparklyr.defaultPackages:
- com.databricks:spark-csv_2.11:1.3.0
- com.datastax.spark:spark-cassandra-connector_2.11:2.0.0-M1
- com.datastax.cassandra:cassandra-driver-core:3.0.2

Sys.setnev setting set for local install of Java and spark, config set to use yml file. Spark connection initiated with:

sc <- spark_connect(master = "spark://<cluster_address>", config = spark_config(file = "config.yml"))

Spark session initiated with:

sparkSession <- sparklyr::invoke_static(sc, org.apache.spark.sql.SparkSession", "builder") %>% 
    sparklyr::invoke("config", "spark.cassandra.connection.host", "<cluster_address>") %>% 
    sparklyr::invoke("getOrCreate")

It all seems fine up to here, (sc connection and sparkSession), but now attempting to access a cassandra table (table_1 in in keyspace_1), which I know exists:

cass_df <- invoke(sparkSession, "read") %>% 
invoke("format", "org.apache.spark.sql.cassandra") %>% 
invoke("option", "keyspace", "keyspace_1") %>% 
invoke("option", "table", "table_1") %>% 
invoke("load")

throws up the following error:

Error: java.lang.IllegalArgumentException: Cannot build a cluster without contact points
at com.datastax.driver.core.Cluster.checkNotEmpty(Cluster.java:123)
at com.datastax.driver.core.Cluster.(Cluster.java:116)
at com.datastax.driver.core.Cluster.buildFrom(Cluster.java:182)
at com.datastax.driver.core.Cluster$Builder.build(Cluster.java:1274)
at com.datastax.spark.connector.cql.DefaultConnectionFactory$.createCluster(CassandraConnectionFactory.scala:92) . . .

回答1:

finally solved it, thanks to a useful tip.I was using the SPARK (with port number) to initialise the SparkSession rather than just the cluster address (where cassandra was located). it works! thanks @user7337271.

来源：https://stackoverflow.com/questions/41877859/unable-to-connect-spark-to-cassandra-db-in-rstudio