This post originated from an RSS feed registered with Scala Buzz by Caoyuan Deng. Original Post: RPC Server for Erlang, In Scala Feed Title: Blogs about Scala from Caoyuan Feed URL: http://blogtrader.org/page/dcaoyuan/feed/entries/atom?tags=scala Feed Description: Blogs about Scala from Caoyuan Deng Latest Scala Buzz Posts Latest Scala Buzz Posts by Caoyuan Deng Latest Posts From Blogs about Scala from Caoyuan

There has been Java code in my previous blog: RPC Server for Erlang, In Java, I'm now try to rewrite it in Scala. With the pattern match that I've been familiar with in Erlang, write the Scala version is really a pleasure. You can compare it with the Java version.

I do not try Scala's actor lib yet, maybe late.

And also, I should port Erlang's jinterface to Scala, since OtpErlangTuple, OtpErlangList should be written in Scala's Tuple and List.

The code is auto-formatted by NetBeans' Scala plugin, and the syntax highlighting is the same as in NetBeans, oh, not exactly.

/*
 * RpcMsg.scala
 *
 */
package net.lightpole.rpcnode

import com.ericsson.otp.erlang.{OtpErlangAtom, OtpErlangList, OtpErlangObject, OtpErlangPid, OtpErlangRef, OtpErlangTuple}

class RpcMsg(val call:OtpErlangAtom,
             val mod :OtpErlangAtom,
             val fun :OtpErlangAtom,
             val args:OtpErlangList,
             val user:OtpErlangPid,
             val to  :OtpErlangPid,
             val tag :OtpErlangRef) {
}

object RpcMsg {
   
   def apply(msg:OtpErlangObject) : Option[RpcMsg] = msg match {
      case tMsg:OtpErlangTuple =>
         tMsg.elements() match {
            /* {'$gen_call', {To, Tag}, {call, Mod, Fun, Args, User}} */
            case Array(head:OtpErlangAtom, from:OtpErlangTuple, request:OtpErlangTuple) =>
               if (head.atomValue.equals("$gen_call")) {
                  (from.elements, request.elements) match {
                     case (Array(to :OtpErlangPid,
                                 tag:OtpErlangRef), Array(call:OtpErlangAtom,
                                                          mod :OtpErlangAtom,
                                                          fun :OtpErlangAtom,
                                                          args:OtpErlangList,
                                                          user:OtpErlangPid)) =>
                        if (call.atomValue.equals("call")) {
                           Some(new RpcMsg(call, mod, fun, args, user, to, tag))
                        } else None
                     case _ => None
                  }
               } else None
            case _ => None
         }
      case _ => None
   }
}

/*
 * RpcNode.scala
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */
package net.lightpole.rpcnode

import com.ericsson.otp.erlang.{OtpAuthException, OtpConnection, OtpErlangAtom, OtpErlangExit, OtpErlangObject, OtpErlangString, OtpErlangTuple, OtpSelf}
import java.io.IOException
import java.net.InetAddress
import java.net.UnknownHostException
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
import java.util.logging.Level
import java.util.logging.Logger


trait Cons {
   val OK     = new OtpErlangAtom("ok")
   val ERROR  = new OtpErlangAtom("error")
   val STOPED = new OtpErlangAtom("stoped")
   val THREAD_POOL_SIZE = 100
}

/**
 *
 * Usage:
 *   $ erl -sname clientnode -setcookie mycookie
 *   (clientnode@cmac)> rpc:call(xnodename@cmac, xnode, parse, []).
 *
 * @author Caoyuan Deng
 */
abstract class RpcNode(xnodeName:String, cookie:String, threadPoolSize:Int) extends Cons {
   
   def this(xnodeName:String, cookie:String) = this(xnodeName, cookie, 100)
   
   private var xSelf:OtpSelf = _
   private var sConnection:OtpConnection = _
   private var execService:ExecutorService = Executors.newFixedThreadPool(threadPoolSize)

   startServerConnection(xnodeName, cookie)
   loop
    
   def startServerConnection(xnodeName:String, cookie:String ) = {
      try {
         xSelf = new OtpSelf(xnodeName, cookie);
         // The node then publishes its port to the Erlang Port Mapper Daemon.
         // This registers the node name and port, making it available to a remote client process.
         // When the port is published it is important to immediately invoke the accept method.
         // Forgetting to accept a connection after publishing the port would be the programmatic
         // equivalent of false advertising
         val registered = xSelf.publishPort();
         if (registered) {
            System.out.println(xSelf.node() + " is ready.");
            /**
             * Accept an incoming connection from a remote node. A call to this
             * method will block until an incoming connection is at least
             * attempted.
             */
            sConnection = xSelf.accept();
         } else {
            System.out.println("There should be an epmd running, start an epmd by running 'erl'.");
         }
      } catch {
         case ex:IOException =>
         case ex:OtpAuthException =>
      }
   }

   def loop : Unit = {
      try {
         val flag = Array(0)
         val msg = sConnection.receive
            
         val task = new Runnable() {
            override
            def run = RpcMsg(msg) match {
               case None =>
                  try {
                     sConnection.send(sConnection.peer.node, new OtpErlangString("unknown request"));
                  } catch {
                     case ex:IOException =>
                  }
               case Some(call) =>
                  val t0 = System.currentTimeMillis

                  flag(0) = processRpcCall(call)

                  System.out.println("Rpc time: " + (System.currentTimeMillis() - t0) / 1000.0)
            }
         }

         execService.execute(task)

         if (flag(0) == -1) {
            System.out.println("Exited")
         } else loop
         
      } catch {
         case ex:IOException => loop
         case ex:OtpErlangExit =>
         case ex:OtpAuthException =>
      }
   }

   /** @throws IOException */
   def sendRpcResult(call:RpcMsg, head:OtpErlangAtom, result:OtpErlangObject)  {
      val tResult = new OtpErlangTuple(Array(head, result))

      // Should specify call.tag here
      val msg = new OtpErlangTuple(Array(call.tag, tResult))
      // Should specify call.to here
      sConnection.send(call.to, msg, 1024 * 1024 * 10)
   }

   /** @abstact */
   def processRpcCall(call:RpcMsg) : Int
}

object RpcCall {   
   def getShortLocalHost : String = getLocalHost(false)

   def getLongLocalHost : String = getLocalHost(true)

   def getLocalHost(longName:Boolean) : String = {
      var localHost = "localhost"
      try {
         localHost = InetAddress.getLocalHost.getHostName;
         if (!longName) {
            /* Make sure it's a short name, i.e. strip of everything after first '.' */
            val dot = localHost.indexOf(".")
            if (dot != -1) localHost = localHost.substring(0, dot)
         }
      } catch {
         case ex:UnknownHostException =>
      }

      localHost
   }
}