Scala Sample Code

Function Description

In Spark applications, use Structured Streaming to call Kafka APIs to obtain word records. Classify word records to obtain the number of records of each word.

Sample Code

The following code snippets are used as an example. For complete codes, see com.huawei.bigdata.spark.examples.SecurityKafkaWordCount.

• For a normal cluster, comment out .option("kafka.security.protocol", protocol) in the 49th line of the com.huawei.bigdata.spark.examples.SecurityKafkaWordCount.scala in the sample code.

• When new data is available in Streaming DataFrame/Dataset, outputMode is used for configuring data written to the Streaming receiver. The default value is append.

object SecurityKafkaWordCount {
  def main(args: Array[String]): Unit = {
    if (args.length < 6) {
      System.err.println("Usage: SecurityKafkaWordCount <bootstrap-servers> " +
        "<subscribe-type> <topics> <protocol> <service> <domain>")
      System.exit(1)
    }

    val Array(bootstrapServers, subscribeType, topics, protocol, service, domain) = args

    val spark = SparkSession
      .builder
      .appName("SecurityKafkaWordCount")
      .getOrCreate()

    import spark.implicits._

    // Create DataSet representing the stream of input lines from Kafka.
    val lines = spark
      .readStream
      .format("kafka")
      .option("kafka.bootstrap.servers", bootstrapServers)
      .option(subscribeType, topics)
      .option("kafka.security.protocol", protocol)
      .option("kafka.sasl.kerberos.service.name", service)
      .option("kafka.kerberos.domain.name", domain)
      .load()
      .selectExpr("CAST(value AS STRING)")
      .as[String]

    // Generate the running word counts.
    val wordCounts = lines.flatMap(_.split(" ")).groupBy("value").count()

    // Start running the query that prints the running counts to the console.
    val query = wordCounts.writeStream
      .outputMode("complete")
      .format("console")
      .start()

    query.awaitTermination()
  }
}