Cluster running on single machine eats too much space of /dev/shm - scala

Question

I am running the example provided by official akka: https://github.com/akka/akka-samples/tree/2.5/akka-sample-cluster-scala.
My OS is: Linux Mint 19 with the latest kernel.
And for the Worker Dial-in Example(Transformation Example), I cannot fully run this example as there is no enough space in /dev/shm. Although I have more than 2GB available space.
The problem is when I launch the first frontend node, it eats some KBs space. When I launch the second one, it eats some MBs space. When I launch the third one, it eats some hundred of MBs space. Further I just cannot even launch the fourth one, it just throws an error which causes the whole cluster down:
[info] Warning: space is running low in /dev/shm (tmpfs) threshold=167,772,160 usable=95,424,512
[info] Warning: space is running low in /dev/shm (tmpfs) threshold=167,772,160 usable=45,088,768
[info] [ERROR] [11/05/2018 21:03:56.156] [ClusterSystem-akka.actor.default-dispatcher-12] [akka://ClusterSystem#127.0.0.1:57246/] swallowing exception during message send
[info] io.aeron.exceptions.RegistrationException: IllegalStateException : Insufficient usable storage for new log of length=50335744 in /dev/shm (tmpfs)
[info] at io.aeron.ClientConductor.onError(ClientConductor.java:174)
[info] at io.aeron.DriverEventsAdapter.onMessage(DriverEventsAdapter.java:81)
[info] at org.agrona.concurrent.broadcast.CopyBroadcastReceiver.receive(CopyBroadcastReceiver.java:100)
[info] at io.aeron.DriverEventsAdapter.receive(DriverEventsAdapter.java:56)
[info] at io.aeron.ClientConductor.service(ClientConductor.java:660)
[info] at io.aeron.ClientConductor.awaitResponse(ClientConductor.java:696)
[info] at io.aeron.ClientConductor.addPublication(ClientConductor.java:371)
[info] at io.aeron.Aeron.addPublication(Aeron.java:259)
[info] at akka.remote.artery.aeron.AeronSink$$anon$1.<init>(AeronSink.scala:103)
[info] at akka.remote.artery.aeron.AeronSink.createLogicAndMaterializedValue(AeronSink.scala:100)
[info] at akka.stream.impl.GraphStageIsland.materializeAtomic(PhasedFusingActorMaterializer.scala:630)
[info] at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:450)
[info] at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:415)
[info] at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:406)
[info] at akka.stream.scaladsl.RunnableGraph.run(Flow.scala:588)
[info] at akka.remote.artery.Association.runOutboundOrdinaryMessagesStream(Association.scala:726)
[info] at akka.remote.artery.Association.runOutboundStreams(Association.scala:657)
[info] at akka.remote.artery.Association.associate(Association.scala:649)
[info] at akka.remote.artery.AssociationRegistry.association(Association.scala:989)
[info] at akka.remote.artery.ArteryTransport.association(ArteryTransport.scala:724)
[info] at akka.remote.artery.ArteryTransport.send(ArteryTransport.scala:710)
[info] at akka.remote.RemoteActorRef.$bang(RemoteActorRefProvider.scala:591)
[info] at akka.actor.ActorRef.tell(ActorRef.scala:124)
[info] at akka.actor.ActorSelection$.rec$1(ActorSelection.scala:265)
[info] at akka.actor.ActorSelection$.deliverSelection(ActorSelection.scala:269)
[info] at akka.actor.ActorSelection.tell(ActorSelection.scala:46)
[info] at akka.actor.ScalaActorSelection.$bang(ActorSelection.scala:280)
[info] at akka.actor.ScalaActorSelection.$bang$(ActorSelection.scala:280)
[info] at akka.actor.ActorSelection$$anon$1.$bang(ActorSelection.scala:198)
[info] at akka.cluster.ClusterCoreDaemon.gossipTo(ClusterDaemon.scala:1330)
[info] at akka.cluster.ClusterCoreDaemon.gossip(ClusterDaemon.scala:1047)
[info] at akka.cluster.ClusterCoreDaemon.gossipTick(ClusterDaemon.scala:1010)
[info] at akka.cluster.ClusterCoreDaemon$$anonfun$initialized$1.applyOrElse(ClusterDaemon.scala:496)
[info] at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:171)
[info] at akka.actor.Actor.aroundReceive(Actor.scala:517)
[info] at akka.actor.Actor.aroundReceive$(Actor.scala:515)
[info] at akka.cluster.ClusterCoreDaemon.aroundReceive(ClusterDaemon.scala:295)
[info] at akka.actor.ActorCell.receiveMessage(ActorCell.scala:588)
[info] at akka.actor.ActorCell.invoke(ActorCell.scala:557)
[info] at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:258)
[info] at akka.dispatch.Mailbox.run(Mailbox.scala:225)
[info] at akka.dispatch.Mailbox.exec(Mailbox.scala:235)
[info] at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
[info] at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
[info] at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
[info] at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
It seems it is sending huge message(48MB+?) to every nodes.
So what's up here? What is the root cause and how shall I fix this?