Cassandra Gossip & seed nodes

Gossip protocol

• Gossip is a peer-to-peer communication protocol in which nodes periodically exchanges state information about themselves and about other nodes they know about.
• the gossip process runs every second and exchanges state messages with up to three other nodes in the cluster.

Seed nodes

• list of seed nodes
  • has no purpose other than bootstraping thre gossip process for new nodes joining the cluster.
  • seed nodes are not a SPOF, nor do they have any other special purpose in cluster operations beyond thre bootstraping of nodes.
• in multiple data-center clusters, include at least one node from each datacenter in three seed list.
• desigating more than a single seed node per datacenter is recommended for fault tolerance.
  • otherwise gossip has to communicate with another datacenter when bootstraping a node.
• making every node a seed node is not recommended because of increased maintenance and reduced gossip performance.
  • recommended to use approximately three nodes per datacenter.