Scala example source code file (CompileSocket.scala)

This example Scala source code file (CompileSocket.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, compiler, compilesocket, int, nil, none, nsc, option, process, seq, socket, string, system, unable, utilities

The CompileSocket.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc

import java.io.{ FileNotFoundException, PrintWriter, FileOutputStream }
import java.security.SecureRandom
import io.{ File, Path, Directory, Socket }
import scala.tools.util.CompileOutputCommon
import scala.reflect.internal.util.StringOps.splitWhere
import scala.sys.process._

trait HasCompileSocket {
  def compileSocket: CompileSocket

  // This is kind of a suboptimal way to identify error situations.
  val errorMarkers = Set("error:", "error found", "errors found", "bad option")
  def isErrorMessage(msg: String) = errorMarkers exists (msg contains _)

  def compileOnServer(sock: Socket, args: Seq[String]): Boolean = {
    var noErrors = true

    sock.applyReaderAndWriter { (in, out) =>
      out println (compileSocket getPassword sock.getPort())
      out println (args mkString "\u0000")

      def loop(): Boolean = in.readLine() match {
        case null => noErrors
        case line =>
          if (isErrorMessage(line))
            noErrors = false

          compileSocket.echo(line)
          loop()
      }
      try loop()
      finally sock.close()
    }
  }
}

/** This class manages sockets for the fsc offline compiler.  */
class CompileSocket extends CompileOutputCommon {
  protected lazy val compileClient: StandardCompileClient = CompileClient
  def verbose = compileClient.verbose

  /** The prefix of the port identification file, which is followed
   *  by the port number.
   */
  protected lazy val dirName = "scalac-compile-server-port"
  protected def cmdName = Properties.scalaCmd

  /** The vm part of the command to start a new scala compile server */
  protected val vmCommand = Properties.scalaHome match {
    case ""       => cmdName
    case dirname  =>
      val trial = File(dirname) / "bin" / cmdName
      if (trial.canRead) trial.path
      else cmdName
  }

  /** The class name of the scala compile server */
  protected val serverClass     = "scala.tools.nsc.CompileServer"
  protected def serverClassArgs = if (verbose) List("-v") else Nil  // debug

  /** A temporary directory to use */
  val tmpDir = {
    val udir  = Option(Properties.userName) getOrElse "shared"
    val f     = (Path(Properties.tmpDir) / ("scala-devel" + udir)).createDirectory()

    if (f.isDirectory && f.canWrite) {
      info("[Temp directory: " + f + "]")
      f
    }
    else fatal("Could not find a directory for temporary files")
  }

  /* A directory holding port identification files */
  val portsDir = (tmpDir / dirName).createDirectory()

  /** The command which starts the compile server, given vm arguments.
    *
    *  @param vmArgs  the argument string to be passed to the java or scala command
    */
  private def serverCommand(vmArgs: Seq[String]): Seq[String] =
    Seq(vmCommand) ++ vmArgs ++ Seq(serverClass) ++ serverClassArgs filterNot (_ == "")

  /** Start a new server. */
  private def startNewServer(vmArgs: String) = {
    val cmd = serverCommand((vmArgs split " ").toSeq)
    info("[Executing command: %s]" format cmd.mkString(" "))

    // Hiding inadequate daemonized implementation from public API for now
    Process(cmd) match {
      case x: ProcessBuilder.AbstractBuilder => x.daemonized().run()
      case x                                 => x.run()
    }
  }

  /** The port identification file */
  def portFile(port: Int) = portsDir / File(port.toString)

  /** Poll for a server port number; return -1 if none exists yet */
  private def pollPort(): Int = portsDir.list.toList match {
    case Nil      => -1
    case x :: xs  => try x.name.toInt finally xs foreach (_.delete())
  }

  /** Get the port number to which a scala compile server is connected;
   *  If no server is running yet, then create one.
   */
  def getPort(vmArgs: String): Int = {
    val maxPolls = 300
    val sleepTime = 25L

    var attempts = 0
    var port = pollPort()

    if (port < 0) {
      info("No compile server running: starting one with args '" + vmArgs + "'")
      startNewServer(vmArgs)
    }
    while (port < 0 && attempts < maxPolls) {
      attempts += 1
      Thread.sleep(sleepTime)
      port = pollPort()
    }
    info("[Port number: " + port + "]")
    if (port < 0)
      fatal("Could not connect to compilation daemon after " + attempts + " attempts.")
    port
  }

  /** Set the port number to which a scala compile server is connected */
  def setPort(port: Int) {
    val file    = portFile(port)
    val secret  = new SecureRandom().nextInt.toString

    try file writeAll secret catch {
      case e @ (_: FileNotFoundException | _: SecurityException) =>
        fatal("Cannot create file: %s".format(file.path))
    }
  }

  /** Delete the port number to which a scala compile server was connected */
  def deletePort(port: Int) = portFile(port).delete()

  /** Get a socket connected to a daemon.  If create is true, then
    * create a new daemon if necessary.  Returns None if the connection
    * cannot be established.
    */
  def getOrCreateSocket(vmArgs: String, create: Boolean = true): Option[Socket] = {
    val maxMillis = 10L * 1000   // try for 10 seconds
    val retryDelay = 50L
    val maxAttempts = (maxMillis / retryDelay).toInt

    def getsock(attempts: Int): Option[Socket] = attempts match {
      case 0    => warn("Unable to establish connection to compilation daemon") ; None
      case num  =>
        val port = if (create) getPort(vmArgs) else pollPort()
        if (port < 0) return None

        Socket.localhost(port).either match {
          case Right(socket)  =>
            info("[Connected to compilation daemon at port %d]" format port)
            Some(socket)
          case Left(err)      =>
            info(err.toString)
            info("[Connecting to compilation daemon at port %d failed; re-trying...]" format port)

            if (attempts % 2 == 0)
              deletePort(port)      // 50% chance to stop trying on this port

            Thread sleep retryDelay // delay before retrying
            getsock(attempts - 1)
        }
    }
    getsock(maxAttempts)
  }

  // XXX way past time for this to be central
  def parseInt(x: String): Option[Int] =
    try   { Some(x.toInt) }
    catch { case _: NumberFormatException => None }

  def getSocket(serverAdr: String): Socket = (
    for ((name, portStr) <- splitWhere(serverAdr, _ == ':', doDropIndex = true) ; port <- parseInt(portStr)) yield
      getSocket(name, port)
  ) getOrElse fatal("Malformed server address: %s; exiting" format serverAdr)

  def getSocket(hostName: String, port: Int): Socket =
    Socket(hostName, port).opt getOrElse fatal("Unable to establish connection to server %s:%d; exiting".format(hostName, port))

  def getPassword(port: Int): String = {
    val ff  = portFile(port)
    val f   = ff.bufferedReader()

    // allow some time for the server to start up
    def check = {
      Thread sleep 100
      ff.length
    }
    if ((Iterator continually check take 50 find (_ > 0)).isEmpty) {
      ff.delete()
      fatal("Unable to establish connection to server.")
    }
    val result = f.readLine()
    f.close()
    result
  }
}


object CompileSocket extends CompileSocket {
}