Effect Gossip Dissemination

Epidemic state dissemination that reaches everyone in O(log N) with no coordinator. A coordinator pushing every update to every node is O(N) work on one machine and a single point of failure; gossip has each node tell a few random peers what it knows, so an update reaches the whole cluster in logarithmic rounds and any node's failure barely dents it. Version vectors make it convergent: nodes merge by keeping the highest version per key, so exchanges are idempotent and order-independent and the system reaches a fixed point where further rounds change nothing. The demo spreads one write to 32 nodes in 3 rounds and converges two concurrent writers. Pinned to effect 4.0.0-beta.98.