Spark Scala Cassandra CSV insert into cassandra - scala

Question

Here is the code below:
Scala Version: 2.11.
Spark Version: 2.0.2.6
Cassandra Version: cqlsh 5.0.1 | Cassandra 3.11.0.1855 | DSE 5.1.3 | CQL spec 3.4.4 | Native protocol v4
I am trying to read from CSV and write to Cassandra Table. I am new to Scala and Spark. Please correct me where I am doing wrong
import org.apache.spark.sql.SparkSession
import org.apache.log4j.{Level, Logger}
import com.datastax
import org.apache.spark.SparkContext
import org.apache.spark.SparkConf
import com.datastax.spark.connector._
import org.apache.spark.sql.SQLContext
import org.apache.spark.sql.{Row, SparkSession}
import org.apache.spark.sql.types.{DoubleType, StringType, StructField, StructType}
import org.apache.spark.sql._
import com.datastax.spark.connector.UDTValue
import com.datastax.spark.connector.mapper.DefaultColumnMapper
object dataframeset {
def main(args: Array[String]): Unit = {
// Cassandra Part
val conf = new SparkConf().setAppName("Sample1").setMaster("local[*]")
val sc = new SparkContext(conf)
sc.setLogLevel("ERROR")
val rdd1 = sc.cassandraTable("tdata", "map")
rdd1.collect().foreach(println)
// Scala Read CSV Part
Logger.getLogger("org").setLevel(Level.ERROR)
Logger.getLogger("akka").setLevel(Level.ERROR)
val spark1 = org.apache.spark.sql.SparkSession
.builder()
.master("local")
.appName("Spark SQL basic example")
.getOrCreate()
val df = spark1.read.format("csv")
.option("header","true")
.option("inferschema", "true")
.load("/Users/tom/Desktop/del2.csv")
import spark1.implicits._
df.printSchema()
val dfprev = df.select(col = "Year","Measure").filter("Category = 'Prevention'" )
// dfprev.collect().foreach(println)
val a = dfprev.select("YEAR")
val b = dfprev.select("Measure")
val collection = sc.parallelize(Seq(a,b))
collection.saveToCassandra("tdata", "map", SomeColumns("sno", "name"))
spark1.stop()
}
}
Error:
Exception in thread "main" java.lang.IllegalArgumentException: Multiple constructors with the same number of parameters not allowed.
Cassandra Table
cqlsh:tdata> desc map
CREATE TABLE tdata.map (
sno int PRIMARY KEY,
name text;
I know I am missing something especially trying to write entire Data frame into Cassandra in one shot. Not I don't know what needs to be done either.
Thanks
tom

Answer 1

You can directly write a dataframe (dataset[Row] in spark 2.x) to cassandra.
You will have to define cassandra host, username and password if authentication is enabled in spark conf to connect to cassandra using somethin like
val conf = new SparkConf(true)
.set("spark.cassandra.connection.host", "CASSANDRA_HOST")
.set("spark.cassandra.auth.username", "CASSANDRA_USERNAME")
.set("spark.cassandra.auth.password", "CASSANDRA_PASSWORD")
OR
val spark1 = org.apache.spark.sql.SparkSession
.builder()
.master("local")
.config("spark.cassandra.connection.host", "CASSANDRA_HOST")
.config("spark.cassandra.auth.username", "CASSANDRA_USERNAME")
.config("spark.cassandra.auth.password", "CASSANDRA_PASSWORD")
.appName("Spark SQL basic example")
.getOrCreate()
val dfprev = df.filter("Category = 'Prevention'" ).select(col("Year").as("yearAdded"),col("Measure").as("Recording"))
dfprev .write
.format("org.apache.spark.sql.cassandra")
.options(Map("table" -> "map", "keyspace" -> "tdata"))
.save()
Dataframe in spark-cassandra-connector