Repeated warning message in Akka cluster sharding

Akka Akka Cluster
1

Hi Team,

When I am trying to recreate entities when a node gets crashed I am getting the below warning message repeatedly

[WARN] [10/28/2019 16:45:44.481] [ReactorCluster-akka.actor.default-dispatcher-42] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:44.481] [ReactorCluster-akka.actor.default-dispatcher-42] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:44.640] [ReactorCluster-akka.actor.default-dispatcher-48] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.162] [ReactorCluster-akka.actor.default-dispatcher-49] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.162] [ReactorCluster-akka.actor.default-dispatcher-49] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.169] [ReactorCluster-akka.actor.default-dispatcher-47] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.169] [ReactorCluster-akka.actor.default-dispatcher-47] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.169] [ReactorCluster-akka.actor.default-dispatcher-47] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.169] [ReactorCluster-akka.actor.default-dispatcher-47] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.169] [ReactorCluster-akka.actor.default-dispatcher-47] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEntity]
[WARN] [10/28/2019 16:45:46.180] [ReactorCluster-akka.actor.default-dispatcher-38] [akka.tcp://ReactorCluster@127.0.0.1:2553/system/sharding/shardregion] Shard must not be empty, dropping message [akka.cluster.sharding.ShardRegion$StartEn

And I didn’t see any entity actor recreation. How to ensure this and guide me If I am wrong.

Below is my configuration details

akka {
  remote{
    netty.tcp{
      hostname="127.0.0.1"
    }
  }
  actor {
    provider = "cluster"
  }
  cluster {
    seed-nodes = [
      "akka.tcp://ReactorCluster@127.0.0.1:2551",
      "akka.tcp://ReactorCluster@127.0.0.1:2552",
      "akka.tcp://ReactorCluster@127.0.0.1:2553"
    ]
  }
}
# Settings for the ClusterShardingExtension
akka.cluster.sharding {
   state-store-mode = ddata
   remember-entities = true
}
2

The warning message Shard must not be empty means your extractShardId implementation returned empty string or null, you’ll have to make sure it always returns a non-empty shard identifier.