A seed node in Akka Cluster is one or more designated nodes used to bootstrap and initialize the cluster. Seed nodes are responsible for helping other nodes discover and join the cluster.
When a node starts, it contacts one or more seed nodes (defined in the configuration) to obtain the current cluster membership information. Once the new node communicates with a seed node, it can successfully join the cluster and participate in distributed operations.
Key Points About Seed Nodes :
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Discovery Mechanism:
- Seed nodes act as a discovery point for other nodes to join the cluster.
- They are not a "special" type of node but regular cluster members with an additional responsibility for the join process.
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Required for Initialization:
- At least one seed node must be available for a cluster to form. Other nodes use the seed nodes to get the cluster state.
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Redundancy:
- Multiple seed nodes are typically defined in the configuration to provide fault tolerance. If one seed node is unavailable, new nodes can contact the next one in the list.
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Not Persistent:
- Seed nodes do not store persistent information about the cluster. They only assist in the discovery process.
