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CustomReceiver.scala
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CustomReceiver.scala
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// scalastyle:off println
package org.apache.spark.examples.streaming
import java.io.{BufferedReader, InputStreamReader}
import java.net.Socket
import java.nio.charset.StandardCharsets
import org.apache.spark.SparkConf
import org.apache.spark.storage.StorageLevel
import org.apache.spark.streaming.{Seconds, StreamingContext}
import org.apache.spark.streaming.receiver.Receiver
/**
* Custom Receiver that receives data over a socket. Received bytes are interpreted as
* text and \n delimited lines are considered as records. They are then counted and printed.
*
* To run this on your local machine, you need to first run a Netcat server
* `$ nc -lk 9999`
* and then run the example
* `$ bin/run-example org.apache.spark.examples.streaming.CustomReceiver localhost 9999`
*/
object CustomReceiver {
def main(args: Array[String]): Unit = {
if (args.length < 2) {
System.err.println("Usage: CustomReceiver <hostname> <port>")
System.exit(1)
}
StreamingExamples.setStreamingLogLevels()
// Create the context with a 1 second batch size
val sparkConf = new SparkConf().setAppName("CustomReceiver")
val ssc = new StreamingContext(sparkConf, Seconds(1))
// Create an input stream with the custom receiver on target ip:port and count the
// words in input stream of \n delimited text (e.g. generated by 'nc')
val lines = ssc.receiverStream(new CustomReceiver(args(0), args(1).toInt))
val words = lines.flatMap(_.split(" "))
val wordCounts = words.map(x => (x, 1)).reduceByKey(_ + _)
wordCounts.print()
ssc.start()
ssc.awaitTermination()
}
}
class CustomReceiver(host: String, port: Int)
extends Receiver[String](StorageLevel.MEMORY_AND_DISK_2) {
def onStart(): Unit = {
// Start the thread that receives data over a connection
new Thread("Socket Receiver") {
override def run(): Unit = { receive() }
}.start()
}
def onStop(): Unit = {
// There is nothing much to do as the thread calling receive()
// is designed to stop by itself isStopped() returns false
}
/** Create a socket connection and receive data until receiver is stopped */
private def receive(): Unit = {
var socket: Socket = null
var userInput: String = null
try {
println(s"Connecting to $host : $port")
socket = new Socket(host, port)
println(s"Connected to $host : $port")
val reader = new BufferedReader(
new InputStreamReader(socket.getInputStream(), StandardCharsets.UTF_8))
userInput = reader.readLine()
while(!isStopped && userInput != null) {
store(userInput)
userInput = reader.readLine()
}
reader.close()
socket.close()
println("Stopped receiving")
restart("Trying to connect again")
} catch {
case e: java.net.ConnectException =>
restart(s"Error connecting to $host : $port", e)
case t: Throwable =>
restart("Error receiving data", t)
}
}
}
// scalastyle:on println