Cassandra's Cluster Internode Communication

Gossip protocol

The nodes of the cluster communicate with each other periodically via a gossip protocol. This allows the nodes to exchange state and topology information about themselves and other nodes they know about within the cluster. New information is gradually spread throughout the cluster via this process. In this way, nodes are able to keep track of which nodes are responsible for which token ranges, so that they can route requests accordingly.

Nodes can also determine which nodes are healthy (reachable) and which are not. The system will not send requests to nodes that are unreachable.

An operator can use administrator tools to instruct a node of the cluster to remove another node that has crashed permanently from the ring. Any partitions belonging to that node will be replicated to a different node from the remaining replicas.

Bootstrapping

The bootstrapping process will allow the first nodes to join the cluster. For this reason, a set of nodes are designated as seed nodes and they can be specified to all the nodes of the cluster via a configuration file or a third-party system during startup.