Modified the interpreter to serve classes to the executors using a Jetty

HTTP server instead of a shared (NFS) file system.

src/scala/spark/repl/ClassServer.scala

+package spark.repl
+
+import java.io.File
+import java.net.InetAddress
+
+import org.eclipse.jetty.server.Server
+import org.eclipse.jetty.server.handler.DefaultHandler
+import org.eclipse.jetty.server.handler.HandlerList
+import org.eclipse.jetty.server.handler.ResourceHandler
+
+
+/**
+ * Exception type thrown by ClassServer when it is in the wrong state 
+ * for an operation.
+ */
+class ServerStateException(message: String) extends Exception(message)
+
+
+/**
+ * An HTTP server used by the interpreter to allow worker nodes to access
+ * class files created as the user types in lines of code. This is just a
+ * wrapper around a Jetty embedded HTTP server.
+ */
+class ClassServer(classDir: File) {
+  private var server: Server = null
+  private var port: Int = -1
+
+  def start() {
+    if (server != null) {
+      throw new ServerStateException("Server is already started")
+    } else {
+      server = new Server(0)
+      val resHandler = new ResourceHandler
+      resHandler.setResourceBase(classDir.getAbsolutePath)
+      val handlerList = new HandlerList
+      handlerList.setHandlers(Array(resHandler, new DefaultHandler))
+      server.setHandler(handlerList)
+      server.start()
+      port = server.getConnectors()(0).getLocalPort()
+    }
+  }
+
+  def stop() {
+    if (server == null) {
+      throw new ServerStateException("Server is already stopped")
+    } else {
+      server.stop()
+      port = -1
+      server = null
+    }
+  }
+
+  /**
+   * Get the URI of this HTTP server (http://host:port)
+   */
+  def uri: String = {
+    if (server == null) {
+      throw new ServerStateException("Server is not started")
+    } else {
+      return "http://" + getLocalIpAddress + ":" + port
+    }
+  }
+
+  /**
+   * Get the local host's IP address in dotted-quad format (e.g. 1.2.3.4)
+   */
+  private def getLocalIpAddress: String = {
+    // Get local IP as an array of four bytes
+    val bytes = InetAddress.getLocalHost().getAddress()
+    // Convert the bytes to ints (keeping in mind that they may be negative)
+    // and join them into a string
+    return bytes.map(b => (b.toInt + 256) % 256).mkString(".")
+  }
+}