Made Akka thread pool and message batch sizes configurable

core/src/main/scala/spark/util/AkkaUtils.scala

@@ -23,6 +23,8 @@ private[spark] object AkkaUtils {
    * ActorSystem itself and its port (which is hard to get from Akka).
    */
   def createActorSystem(name: String, host: String, port: Int): (ActorSystem, Int) = {
+    val akkaThreads = System.getProperty("spark.akka.threads", "4").toInt
+    val akkaBatchSize = System.getProperty("spark.akka.batchSize", "15").toInt
     val akkaConf = ConfigFactory.parseString("""
       akka.daemonic = on
       akka.event-handlers = ["akka.event.slf4j.Slf4jEventHandler"]
@@ -31,9 +33,9 @@ private[spark] object AkkaUtils {
       akka.remote.netty.hostname = "%s"
       akka.remote.netty.port = %d
       akka.remote.netty.connection-timeout = 1s
-      akka.remote.netty.execution-pool-size = 8
-      akka.actor.default-dispatcher.throughput = 30
-      """.format(host, port))
+      akka.remote.netty.execution-pool-size = %d
+      akka.actor.default-dispatcher.throughput = %d
+      """.format(host, port, akkaThreads, akkaBatchSize))
 
     val actorSystem = ActorSystem("spark", akkaConf, getClass.getClassLoader)