The idea of relying on scuttlebutt reconciliation and phi-accrual detection is borrowed from Cassandra, itself borrowing it from DynamoDB. Rather than

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2025-01-10 23:00:06

The idea of relying on scuttlebutt reconciliation and phi-accrual detection is borrowed from Cassandra, itself borrowing it from DynamoDB.

Rather than sending the entire state, the algorithm makes it possibly to only transfer updates or deltas of the state. In addition, delta can be partial in order to fit a UDP packet.

Not receiving any update from node for a given amount of time can therefore be regarded as a sign of failure. Rather than using a hard threshold, we use phi-accrual detection to dynamically compute a threshold.

In order to get a constant flow of updates to feed into phi-accrual detection, chitchat's node state includes a key-value called heartbeat. The heartbeat of a given node, starts at 0, and is incremented once after each round of gossip initiated.

Nodes then report all heartbeat updates to a phi-accrual detector to assess the liveness of this node. Liveness is a local concept. Every single node computes its own vision of the liveness of all other nodes.