throttle challenges socket messages

modules/challenge/src/main/ChallengeApi.scala

@@ -148,22 +148,26 @@ final class ChallengeApi(
 
   private def uncacheAndNotify(c: Challenge): Unit = {
     c.destUserId ?? countInFor.invalidate
-    c.destUserId ?? notify
-    c.challengerUserId ?? notify
+    c.destUserId ?? notifyUser.apply
+    c.challengerUserId ?? notifyUser.apply
     socketReload(c.id)
   }
 
   private def socketReload(id: Challenge.ID): Unit =
     socket.foreach(_ reload id)
 
-  private def notify(userId: User.ID): Funit =
-    for {
-      all  <- allFor(userId)
-      lang <- userRepo langOf userId map I18nLangPicker.byStrOrDefault
-    } yield Bus.publish(
-      SendTo(userId, lila.socket.Socket.makeMessage("challenges", jsonView(all)(lang))),
-      "socketUsers"
-    )
+  private object notifyUser {
+    private val throttler = new lila.hub.EarlyMultiThrottler(logger)
+    def apply(userId: User.ID): Unit = throttler(userId, 2.seconds) {
+      for {
+        all  <- allFor(userId)
+        lang <- userRepo langOf userId map I18nLangPicker.byStrOrDefault
+      } yield Bus.publish(
+        SendTo(userId, lila.socket.Socket.makeMessage("challenges", jsonView(all)(lang))),
+        "socketUsers"
+      )
+    }
+  }
 
   // work around circular dependency
   private var socket: Option[ChallengeSocket] = None

modules/challenge/src/main/package.scala

@@ -5,4 +5,6 @@ import org.joda.time.DateTime
 package object challenge extends PackageObject {
 
   private[challenge] def inTwoWeeks = DateTime.now plusWeeks 2
+
+  private[challenge] val logger = lila log "challenge"
 }