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Socket issues in a simple Scala TCP server

I am new to Scala, so the question may be quite simple, although I spent some time resolving it. I have a simple Scala TCP server (no actors, one thread):

import java.io._
import java.net._

object Application {
  def readSocket(socket: Socket): String = {
    val bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream))
    var request = ""
    var line = ""
    do {
      line = bufferedReader.readLine()
      if (line == null) {
        println("Stream terminated")
        return request
      }
      request += line + "\n"
    } while (line != "")
    request
  }

  def writeSocket(socket: Socket, string: String) {
    val out: PrintWriter = new PrintWriter(new OutputStreamWriter(socket.getOutputStream))
    out.println(string)
    out.flush()
  }

  def main(args: Array[String]) {
    val port = 8000
    val serverSocket = new ServerSocket(port)
    while (true) {
      val socket = serverSocket.accept()
      readSocket(socket)
      writeSocket(socket, "HTTP/1.1 200 OK\r\n\r\nOK")
      socket.close()
    }
  }
}

The server listens localhost:8000for incoming requests and sends an HTTP response with a single word OKin the body. Then I launch Apache Benchmark as follows:

ab -c 1000 -n 10000 http://localhost:8000/

which works great for the first time. The second time I run ab, it freezes, producing the following output in netstat -a | grep 8000:

....
tcp        0      0 localhost.localdo:43709 localhost.localdom:8000 FIN_WAIT2  
tcp        0      0 localhost.localdo:43711 localhost.localdom:8000 FIN_WAIT2  
tcp        0      0 localhost.localdo:43717 localhost.localdom:8000 FIN_WAIT2  
tcp        0      0 localhost.localdo:43777 localhost.localdom:8000 FIN_WAIT2  
tcp        0      0 localhost.localdo:43722 localhost.localdom:8000 FIN_WAIT2  
tcp        0      0 localhost.localdo:43725 localhost.localdom:8000 FIN_WAIT2  
tcp6       0      0 [::]:8000               [::]:*                  LISTEN     
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43724 CLOSE_WAIT 
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43786 CLOSE_WAIT 
tcp6       1      0 localhost.localdom:8000 localhost.localdo:43679 CLOSE_WAIT 
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43735 CLOSE_WAIT 
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43757 CLOSE_WAIT 
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43754 CLOSE_WAIT 
tcp6      83      0 localhost.localdom:8000 localhost.localdo:43723 CLOSE_WAIT
....

. : ab script Node.js . , TCP-,

sudo sysctl -w net.ipv4.tcp_tw_recycle=1
sudo sysctl -w net.ipv4.tcp_tw_reuse=1

- , ?

. :

    if (line == null) {
      println("Stream terminated")
      return request
    }
+5
2

() , . -, , , . , socket, readSocket, , , bufferedReader.readLine() null . :

  • sysctl -w net.core.somaxconn=65535

  • ServerSocket, :

    val maxQueue = 50000
val serverSocket = new ServerSocket(port, maxQueue)

EC2 m1.large, . Akka :

import akka.actor._
import java.net.InetSocketAddress
import akka.util.ByteString

class TCPServer(port: Int) extends Actor {

  override def preStart {
    IOManager(context.system).listen(new InetSocketAddress(port))
  }

  def receive = {
    case IO.NewClient(server) =>
      server.accept()
    case IO.Read(rHandle, bytes) => {
      val byteString = ByteString("HTTP/1.1 200 OK\r\n\r\nOK")
      rHandle.asSocket.write(byteString)
      rHandle.close()
    }
  }
}

object Application {
  def main(args: Array[String]) {
    val port = 8000
    ActorSystem().actorOf(Props(new TCPServer(port)))
  }
}
+2

-, ab. - :

echo "I'm\nHappy\n" | nc -vv localhost 8000

-, . BufferedReader.readLine() null. . , , . ab, , . , .

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