use Monoid[Future[_]] to append concurrent futures

modules/hub/src/main/ActorMap.scala

@@ -6,6 +6,7 @@ import actorApi.map._
 import akka.actor._
 import akka.pattern.{ ask, pipe }
 import makeTimeout.short
+import scalaz.Monoid
 
 trait ActorMap[A <: Actor] extends Actor {
 
@@ -42,10 +43,16 @@ trait ActorMap[A <: Actor] extends Actor {
     actors.values foreach (_ ! msg)
   }
 
+  // sequential
   protected def askAll(msg: Any): Fu[List[Any]] = {
     actors.values.toList map (_ ? msg)
   } sequenceFu
 
+  // concurrent
+  protected def zipAll[A: Monoid: Manifest](msg: Any): Fu[A] = {
+    actors.values.toList map (_ ? msg mapTo manifest[A])
+  }.suml
+
   protected def get(id: String): Fu[ActorRef] = self ? Get(id) mapTo manifest[ActorRef]
 
   protected def withActor(id: String)(op: ActorRef ⇒ Unit) = get(id) foreach op

modules/socket/src/main/SocketHubActor.scala

@@ -1,14 +1,14 @@
 package lila.socket
 
+import actorApi._
 import akka.actor._
 import akka.pattern.{ ask, pipe }
+import makeTimeout.short
 import play.api.libs.json._
 
-import actorApi._
 import lila.hub.actorApi.{ GetNbMembers, NbMembers, WithUserIds, WithSocketUserIds, SendTo, SendTos }
 import lila.hub.ActorMap
 import lila.socket.actorApi.{ Connected ⇒ _, _ }
-import makeTimeout.short
 
 trait SocketHubActor[A <: SocketActor[_]] extends Socket with ActorMap[A] {
 
@@ -16,8 +16,7 @@ trait SocketHubActor[A <: SocketActor[_]] extends Socket with ActorMap[A] {
 
   private def _socketHubReceive: Receive = {
 
-    case msg @ GetNbMembers ⇒
-      askAll(msg) mapTo manifest[List[Int]] map (_.sum) pipeTo sender
+    case msg @ GetNbMembers       ⇒ zipAll[Int](msg) pipeTo sender
 
     case msg @ NbMembers(_)       ⇒ tellAll(msg)