Get process PID via reflection, use it to kill -15 it before forcib…

…ly destroying it.

src/main/scala/scala/sys/process/ProcessWithPid.scala

@@ -0,0 +1,48 @@
+package scala.sys.process
+
+import java.lang.{Process => JProcess}
+import sbt.{Level, Logger}
+import scala.util.control.NonFatal
+
+case class ProcessWithPid(process: Process, pid: Option[Long])
+
+object ProcessWithPid {
+  private def reflectJProcess(p: Process.SimpleProcess): JProcess = {
+    val field = p.getClass.getDeclaredField("p")
+    field.setAccessible(true)
+    field.get(p).asInstanceOf[JProcess]
+  }
+
+  // Java 9+ has a `Process#pid()` method, but Java 8 and below have a private `Process#pid` field
+  // We first try to reflect on the method and then fall back to reflecting on the field
+  private def reflectJProcessPid(p: JProcess): Long =
+    try {
+      val method = classOf[JProcess].getMethod("pid")
+      method.invoke(p) match {
+        case pid: java.lang.Long => pid
+        case pid => throw new RuntimeException(s"Expected process PID ($pid) to be a Long, but it was a ${pid.getClass.getName}")
+      }
+    } catch {
+      case e: NoSuchMethodException =>
+        val field = p.getClass.getDeclaredField("pid")
+        field.setAccessible(true)
+        field.getLong(p)
+    }
+
+  def apply(process: Process, log: Logger): ProcessWithPid =
+    try {
+      process match {
+        case p: Process.SimpleProcess =>
+          val jp = reflectJProcess(p)
+          val pid = reflectJProcessPid(jp)
+          ProcessWithPid(process, Some(pid))
+
+        case p =>
+          throw new RuntimeException(s"Expected app process to be a Process.SimpleProcess but it was a ${p.getClass.getName}")
+      }
+    } catch {
+      case NonFatal(e) =>
+        log.log(Level.Warn, s"Failed to determine process PID: $e")
+        ProcessWithPid(process, None)
+    }
+}

src/main/scala/spray/revolver/Actions.scala

@@ -19,7 +19,7 @@ package spray.revolver
 import sbt.Keys._
 import sbt.{Fork, ForkOptions, LoggedOutput, Logger, Path, ProjectRef, State, complete}
 import java.io.File
-import scala.sys.process.Process
+import scala.sys.process.ProcessWithPid
 
 object Actions {
   import Utilities._
@@ -129,13 +129,13 @@ object Actions {
   def formatAppName(projectName: String, projectColor: String, color: String = "[YELLOW]"): String =
     "[RESET]%s%s[RESET]%s" format (projectColor, projectName, color)
 
-  def forkRun(config: ForkOptions, mainClass: String, classpath: Seq[File], options: Seq[String], log: Logger, extraJvmArgs: Seq[String]): Process = {
+  def forkRun(config: ForkOptions, mainClass: String, classpath: Seq[File], options: Seq[String], log: Logger, extraJvmArgs: Seq[String]): ProcessWithPid = {
     log.info(options.mkString("Starting " + mainClass + ".main(", ", ", ")"))
     val scalaOptions = "-classpath" :: Path.makeString(classpath) :: mainClass :: options.toList
     val newOptions = config
       .withOutputStrategy(config.outputStrategy getOrElse LoggedOutput(log))
       .withRunJVMOptions(config.runJVMOptions ++ extraJvmArgs)
 
-    Fork.java.fork(newOptions, scalaOptions)
+    ProcessWithPid(Fork.java.fork(newOptions, scalaOptions), log)
   }
 }

src/main/scala/spray/revolver/AppProcess.scala

@@ -17,22 +17,38 @@
 package spray.revolver
 
 import java.lang.{Runtime => JRuntime}
+import java.util.concurrent.TimeUnit
 import sbt.{Logger, ProjectRef}
 
-import scala.sys.process.Process
+import scala.sys.process.ProcessWithPid
 
 /**
  * A token which we put into the SBT state to hold the Process of an application running in the background.
  */
-case class AppProcess(projectRef: ProjectRef, consoleColor: String, log: Logger)(process: Process) {
+case class AppProcess(projectRef: ProjectRef, consoleColor: String, log: Logger)(process: ProcessWithPid) {
   val shutdownHook = createShutdownHook("... killing ...")
 
+  private def destroyProcess(): Unit = process.process.destroy()
+
+  private def killProcess(pid: Long): Unit = {
+    val exited = try {
+      JRuntime.getRuntime.exec(s"kill -15 $pid").waitFor(10, TimeUnit.SECONDS)
+    } catch { case e: InterruptedException => true }
+
+    if (!exited) destroyProcess()
+  }
+
+  private def stopProcess(): Int = {
+    process.pid.fold(destroyProcess())(killProcess)
+    process.process.exitValue()
+  }
+
   def createShutdownHook(msg: => String) =
     new Thread(new Runnable {
       def run() {
         if (isRunning) {
           log.info(msg)
-          process.destroy()
+          stopProcess()
         }
       }
     })
@@ -42,7 +58,7 @@ case class AppProcess(projectRef: ProjectRef, consoleColor: String, log: Logger)
   val watchThread = {
     val thread = new Thread(new Runnable {
       def run() {
-        val code = process.exitValue()
+        val code = process.process.exitValue()
         finishState = Some(code)
         log.info("... finished with exit code %d" format code)
         unregisterShutdownHook()
@@ -58,8 +74,7 @@ case class AppProcess(projectRef: ProjectRef, consoleColor: String, log: Logger)
 
   def stop() {
     unregisterShutdownHook()
-    process.destroy()
-    process.exitValue()
+    stopProcess()
   }
 
   def registerShutdownHook() {