Scala example source code file (CompileServer.scala)

This example Scala source code file (CompileServer.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

compile, compiler, compileserver, consolereporter, global, maxcharge, nsc, reflection, set, setting, settings, standardcompileserver, string, utilities

The CompileServer.scala Scala example source code

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

package scala.tools.nsc

import java.io.PrintStream
import scala.tools.nsc.reporters.{Reporter, ConsoleReporter}
import scala.reflect.internal.util.FakePos //Position
import scala.tools.util.SocketServer
import settings.FscSettings

/**
 *  The server part of the fsc offline compiler.  It awaits compilation
 *  commands and executes them.  It caches a compiler instance so
 *  that it can respond more quickly.
 *
 *  @author Martin Odersky
 *  @version 1.0
 */
class StandardCompileServer extends SocketServer {
  lazy val compileSocket: CompileSocket = CompileSocket

  private var compiler: Global = null
  private def clearCompiler() = compiler = null

  var reporter: ConsoleReporter = _
  var shutdown = false
  var verbose = false

  val MaxCharge = 0.8

  private val runtime = Runtime.getRuntime()
  import runtime.{ totalMemory, freeMemory, maxMemory }

  /** Create a new compiler instance */
  def newGlobal(settings: Settings, reporter: Reporter) =
    new Global(settings, reporter) {
      override def inform(msg: String) = out.println(msg)
    }

  override def timeout() {
    if (!compileSocket.portFile(port).exists)
      fatal("port file no longer exists; skipping cleanup")
  }

  def printMemoryStats() {
    def mb(bytes: Long) = "%dMB".format(bytes / 1000000)
    info("New session: total memory = %s, max memory = %s, free memory = %s".format(
      mb(totalMemory), mb(maxMemory), mb(freeMemory)))
  }

  def isMemoryFullEnough() = {
    runtime.gc()
    (totalMemory - freeMemory).toDouble / maxMemory.toDouble > MaxCharge
  }

  /** Problematically, Settings are only considered equal if every setting
   *  is exactly equal.  In fsc this immediately breaks down because the randomly
   *  chosen temporary outdirs differ between client and server.  Among other
   *  things.  Long term we could use a meaningful equality; short term I'm just
   *  ignoring options which I can see causing a new compiler instance every time
   *  and which do not interestingly influence compilation products.
   */
  def unequalSettings(s1: Settings, s2: Settings): Set[Settings#Setting] = {
    val ignoreSettings = Set("-d", "-encoding", "-currentDir")
    def trim (s: Settings): Set[Settings#Setting] = (
      s.userSetSettings.toSet[Settings#Setting] filterNot (ss => ignoreSettings exists (ss respondsTo _))
    )
    val ss1 = trim(s1)
    val ss2 = trim(s2)

    (ss1 union ss2) -- (ss1 intersect ss2)
  }

  def session() {
    val password        = compileSocket getPassword port
    val guessedPassword = in.readLine()
    val input           = in.readLine()

    def fscError(msg: String): Unit = out println (
      FakePos("fsc") + msg + "\n  fsc -help  gives more information"
    )
    if (input == null || password != guessedPassword)
      return

    val args        = input.split("\u0000", -1).toList
    val newSettings = new FscSettings(fscError)
    val command     = new OfflineCompilerCommand(args, newSettings)
    this.verbose    = newSettings.verbose.value

    info("Settings after normalizing paths: " + newSettings)
    if (!command.files.isEmpty) info("Input files after normalizing paths: " + (command.files mkString ","))
    printMemoryStats()

    // Update the idle timeout if given
    if (!newSettings.idleMins.isDefault) {
      val mins = newSettings.idleMins.value
      if (mins == 0) echo("Disabling idle timeout on compile server.")
      else echo("Setting idle timeout to " + mins + " minutes.")

      this.idleMinutes = mins
    }
    if (newSettings.shutdown.value) {
      shutdown = true
      return out.println("[Compile server exited]")
    }
    if (newSettings.reset.value) {
      clearCompiler()
      out.println("[Compile server was reset]")
      if (command.files.isEmpty)
        return
    }

    reporter = new ConsoleReporter(newSettings, in, out) {
      // disable prompts, so that compile server cannot block
      override def displayPrompt() = ()
    }
    def isCompilerReusable: Boolean = {
      if (compiler == null) {
        info("[Creating new instance for compile server.]")
        info("[Compiler version: " + Properties.versionString + ".]")
        return false
      }
      val unequal = unequalSettings(newSettings, compiler.settings)
      if (unequal.nonEmpty) {
        info("[Replacing compiler with new instance because settings are unequal.]")
        info("[Asymmetric settings: " + unequal.mkString(", ") + "]")
      }
      unequal.isEmpty
    }

    if (command.shouldStopWithInfo)
      reporter.echo(command.getInfoMessage(newGlobal(newSettings, reporter)))
    else if (command.files.isEmpty)
      reporter.echo(command.usageMsg)
    else {
      if (isCompilerReusable) {
        info("[Reusing existing Global instance.]")
        compiler.currentSettings = newSettings
        compiler.reporter = reporter
      }
      else {
        compiler = newGlobal(newSettings, reporter)
      }
      val c = compiler
      try new c.Run() compile command.files
      catch {
        case ex @ FatalError(msg) =>
          reporter.error(null, "fatal error: " + msg)
          clearCompiler()
        case ex: Throwable =>
          warn("Compile server encountered fatal condition: " + ex)
          shutdown = true
          throw ex
      }
    }
    reporter.printSummary()
    if (isMemoryFullEnough()) {
      info("Nulling out compiler due to memory utilization.")
      clearCompiler()
    }
  }
}


object CompileServer extends StandardCompileServer {
  /** A directory holding redirected output */
  private lazy val redirectDir = (compileSocket.tmpDir / "output-redirects").createDirectory()

  private def createRedirect(filename: String) =
    new PrintStream((redirectDir / filename).createFile().bufferedOutput())

  def main(args: Array[String]) =
    execute(() => (), args)

  /**
   * Used for internal testing. The callback is called upon
   * server start, notifying the caller that the server is
   * ready to run. WARNING: the callback runs in the
   * server's thread, blocking the server from doing any work
   * until the callback is finished. Callbacks should be kept
   * simple and clients should not try to interact with the
   * server while the callback is processing.
   */
  def execute(startupCallback : () => Unit, args: Array[String]) {
    val debug = args contains "-v"

    if (debug) {
      echo("Starting CompileServer on port " + port)
      echo("Redirect dir is " + redirectDir)
    }

    Console.withErr(createRedirect("scala-compile-server-err.log")) {
      Console.withOut(createRedirect("scala-compile-server-out.log")) {
        Console.err.println("...starting server on socket "+port+"...")
        Console.err.flush()
        compileSocket setPort port
        startupCallback()
        run()

        compileSocket deletePort port
      }
    }
  }
}