One node knows. Each round, infected nodes tell 'fanout' random others. O(log N) rounds.

What you're seeing

Gossip (epidemic) protocols spread information by repeated random pairwise exchange. Each round, every "infected" node tells K random others. Total time to full propagation: O(log N) rounds.

Used by Cassandra, Dynamo, Consul, SWIM for cluster membership. Robust to node failures (rumor finds another path) but high message traffic for small clusters; very efficient for large.

★ KEY TAKEAWAY
Gossip spreads information in O(log N) rounds. Each round, every infected node tells K random others. Used by Cassandra, Consul.
▶ WHAT TO TRY
  • Click Start gossip and watch a rumor spread through 50 nodes.
  • Increase Fanout to see faster propagation.
  • ~log₂(50) ≈ 6 rounds to reach everyone.
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