For each RDD in a DStream how do I convert this to an array or some other typical Java data type?

问题

I would like to convert a DStream into an array, list, etc. so I can then translate it to json and serve it on an endpoint. I'm using apache spark, injecting twitter data. How do I preform this operation on the Dstream statuses? I can't seem to get anything to work other than print().

import org.apache.spark._
import org.apache.spark.SparkContext._
import org.apache.spark.streaming._
import org.apache.spark.streaming.twitter._
import org.apache.spark.streaming.StreamingContext._
import TutorialHelper._
object Tutorial {
  def main(args: Array[String]) {

    // Location of the Spark directory 
    val sparkHome = "/opt/spark"

    // URL of the Spark cluster
    val sparkUrl = "local[8]"

    // Location of the required JAR files 
    val jarFile = "target/scala-2.10/tutorial_2.10-0.1-SNAPSHOT.jar"

    // HDFS directory for checkpointing
    val checkpointDir = "/tmp" 

    // Configure Twitter credentials using twitter.txt
    TutorialHelper.configureTwitterCredentials()

    val ssc = new StreamingContext(sparkUrl, "Tutorial", Seconds(1), sparkHome, Seq(jarFile))

    val filters = Array("#americasgottalent", "iamawesome")
    val tweets = TwitterUtils.createStream(ssc, None, filters)

    val statuses = tweets.map(status => status.getText())

    val arry = Array("firstval")
    statuses.foreachRDD {
         arr :+ _.collect()
    }

    ssc.checkpoint(checkpointDir)

    ssc.start()
    ssc.awaitTermination()
  }
}

回答1:

If your RDD is statuses you can do.

val arr = new ArrayBuffer[String]();
statuses.foreachRDD {
    arr ++= _.collect() //you can now put it in an array or d w/e you want with it
    ...
}

Keep in mind this could end up being way more data than you want in your driver since a DStream can be huge.

回答2:

Turns our you were close, but what I ended up looking for is.

statuses.foreachRDD( rdd => {
    for(item <- rdd.collect().toArray) {
        println(item);
    }
})

来源：https://stackoverflow.com/questions/24772799/for-each-rdd-in-a-dstream-how-do-i-convert-this-to-an-array-or-some-other-typica

标签

scala

apache-spark

spark-streaming

dstream