SnapshotStore doesn't reply with SnapshotNotFound some times

[xirc]

SnapshotStore (or ShardSnapshotStore) should reply with SnapshotNotFound if it has no EntitySnapshot and is saving an EntitySnapshot. For example, when an entity (ReplicatedEntityBehavior) is recovering, the entity waits for a response from ShardSnapshotStore. If ShardSnapshotStore replies with SnapshotNotFound, the entity can continue its recovery. If ShardSnapshotStore replies with nothing, the entity might get recovery timed out. This case might rarely happen because the entity might be already recovered when SnapshotStore receives a SaveSnapshot command.

Related code:

• https://github.com/lerna-stack/akka-entity-replication/blob/v2.1.0/src/main/scala/lerna/akka/entityreplication/typed/internal/behavior/Recovering.scala#L36-L83
• https://github.com/lerna-stack/akka-entity-replication/blob/v2.1.0/src/main/scala/lerna/akka/entityreplication/raft/snapshot/SnapshotStore.scala#L93-L96