Hi,

I have been using Akka for few months already but it's the first time I am 
playing with Akka Cluster. I am trying to have a clustered app that will 
consist on 3 nodes. Each node will be reading from a messaging queue and 
then sending the data to the correct actor through a consistent-hashing 
cluster-aware router based on different parameters. When starting the 
cluster I have no issues. I can see all the nodes joining the cluster and 
they all are marked as Up. However, the moment I start to send data through 
the messaging queue I get few dead-letter messages like these ones (sorry 
for the long log): 

*2014-10-20 01:42:40,051 INFO  [Main-akka.actor.default-dispatcher-4] - 
Message [akka.remote.transport.AssociationHandle$Disassociated] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.145.54%3A56388-3#-919015728]
 
was not delivered. [1] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:40,065 WARN  [Main-akka.actor.default-dispatcher-4] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Disassociated].*
*2014-10-20 01:42:40,073 INFO  [Main-akka.actor.default-dispatcher-4] - 
Message 
[akka.remote.transport.ActorTransportAdapter$DisassociateUnderlying] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.145.54%3A56388-3#-919015728]
 
was not delivered. [2] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:40,850 WARN  [Main-akka.actor.default-dispatcher-30] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*
*2014-10-20 01:42:40,864 INFO  [Main-akka.actor.default-dispatcher-23] - 
Message [akka.remote.transport.AssociationHandle$Disassociated] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/endpointManager/reliableEndpointWriter-akka.tcp%3A%2F%2FMain%40node2.myapp.com%3A3351-1/endpointWriter/endpointReader-akka.tcp%3A%2F%2FMain%40node2.myapp.com%3A3351-0#-1831360146]
 
was not delivered. [3] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:40,868 INFO  [Main-akka.actor.default-dispatcher-23] - 
Message [akka.remote.transport.AssociationHandle$Disassociated] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.144.222%3A48127-2#-1180771271]
 
was not delivered. [4] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,486 INFO  [Main-akka.actor.default-dispatcher-30] - 
Message [akka.remote.transport.AssociationHandle$Disassociated] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.144.217%3A58082-1#-1870263836]
 
was not delivered. [5] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,487 INFO  [Main-akka.actor.default-dispatcher-30] - 
Message [akka.remote.transport.AssociationHandle$Disassociated] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.144.217%3A58082-1#-1870263836]
 
was not delivered. [6] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,488 WARN  [Main-akka.actor.default-dispatcher-30] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Disassociated].*
*2014-10-20 01:42:41,490 INFO  [Main-akka.actor.default-dispatcher-30] - 
Message 
[akka.remote.transport.ActorTransportAdapter$DisassociateUnderlying] from 
Actor[akka://Main/deadLetters] to 
Actor[akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.144.217%3A58082-1#-1870263836]
 
was not delivered. [7] dead letters encountered. This logging can be turned 
off or adjusted with configuration settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,785 INFO  [Main-akka.actor.default-dispatcher-28] - 
Message [akka.cluster.ClusterHeartbeatSender$Heartbeat] from 
Actor[akka://Main/system/cluster/core/daemon/heartbeatSender#315593511] to 
Actor[akka://Main/deadLetters] was not delivered. [8] dead letters 
encountered. This logging can be turned off or adjusted with configuration 
settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,787 INFO  [Main-akka.actor.default-dispatcher-28] - 
Message [akka.cluster.ClusterHeartbeatSender$Heartbeat] from 
Actor[akka://Main/system/cluster/core/daemon/heartbeatSender#315593511] to 
Actor[akka://Main/deadLetters] was not delivered. [9] dead letters 
encountered. This logging can be turned off or adjusted with configuration 
settings 'akka.log-dead-letters' and 
'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:41,788 INFO  [Main-akka.actor.default-dispatcher-28] - 
Message [akka.cluster.ClusterHeartbeatSender$Heartbeat] from 
Actor[akka://Main/system/cluster/core/daemon/heartbeatSender#315593511] to 
Actor[akka://Main/deadLetters] was not delivered. [10] dead letters 
encountered, no more dead letters will be logged. This logging can be 
turned off or adjusted with configuration settings 'akka.log-dead-letters' 
and 'akka.log-dead-letters-during-shutdown'.*
*2014-10-20 01:42:46,751 WARN  [Main-akka.actor.default-dispatcher-25] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*
*2014-10-20 01:42:46,755 WARN  [Main-akka.actor.default-dispatcher-25] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*
*2014-10-20 01:42:54,205 WARN  [Main-akka.actor.default-dispatcher-3] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*
*2014-10-20 01:42:54,213 WARN  [Main-akka.actor.default-dispatcher-3] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*
*2014-10-20 01:42:54,357 WARN  [Main-akka.actor.default-dispatcher-27] - 
Association with remote system [akka.tcp://[email protected]:3351] has 
failed, address is now gated for [5000] ms. Reason is: [Failed to write 
message to the transport].*

And I keep getting those messages until I stop sending data. Also, I have 
noticed some actors are using the hostname (
*akka.tcp://[email protected]:3351) *and some the private network IPs (
akka://Main/system/transports/akkaprotocolmanager.tcp0/akkaProtocol-tcp%3A%2F%2FMain%4010.196.145.54%3A56388-3#-919015728*),
 
*is this an issue?

Moreover, when I increase the load I start seeing messages that some nodes 
become UNREACHABLE and few seconds later the become REACHABLE again. I have 
been reading other threads in this group list and I followed few tips like 
having a cluster dispatcher and tweaking the cluster failure detector. My 
configuration looks like this:

*  cluster {*
*    seed-nodes = ["akka.tcp://[email protected]:3351"]*
*    use-dispatcher = cluster-dispatcher*
*    gossip-interval = 5s*
*    unreachable-nodes-reaper-interval = 5s*
*    auto-down-unreachable-after = 300s*
*    seed-node-timeout=60s*

*    failure-detector {*
*      acceptable-heartbeat-pause = 15s*
*      threshold = 15*
*      heartbeat-interval = 3s*
*      monitored-by-nr-of-members = 5*
*      expected-response-after = 15s*
*    }*

*    metrics {*
*      enabled = off*
*    }*
*  }*
*...*
*cluster-dispatcher {*
*  type = "Dispatcher"*
*  executor = "fork-join-executor"*
*  fork-join-executor {*
*    parallelism-min = 2*
*    parallelism-max = 4*
*  }*
*  extensions = 
["com.romix.akka.serialization.kryo.KryoSerializationExtension$"]*
*}*

And my actor deployment configuration looks like this:

*      /app/dataProcessor {*
*        router = balancing-pool*
*        nr-of-instances = 1*
*      }*

*      /app/smartFilterRouter {*
*        router = consistent-hashing-group*
*        nr-of-instances = 1000*
*        routees.paths = ["/user/app/dataProcessor"]*
*        cluster {*
*          enabled = on*
*          max-nr-of-instances-per-node = 1*
*          allow-local-routees = on*
*          extensions = 
["com.romix.akka.serialization.kryo.KryoSerializationExtension$"]*
*        }*
*      }*

What can I tweak in order to get Akka Cluster to work properly? Am I 
missing any important configuration?

Thank you for your help and time,

Hector Veiga.

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