Coalesced heartbeat

[akiradeveloper]

Raft node contains multiple Raft processes, each belongs to some lane or shard.

A Raft process periodically sends heartbeat to followers if it is a leader. Now, let's think about optimization by batching heartbeats.

If two Raft processes in node A both send heartbeat to node B, there is a chance to coalesce these heartbeats.

Math: Let's assume there are N nodes and L lanes and processes are evenly distributed (K per lane), what is the effect of this optimization?

[akiradeveloper]

I don't know this is correct.

Totally, there are LK heartbeats periodically.
The directed path of two nodes in the cluster is N(N-1).
So, LK/N(N-1) is the expected number of heartbeats on a directed path, which is the coalescing number to calculate.

Example:
K=5, L=1000, N=8
5000/56 = 100
We can reduce the heartbeats to 1%.

[akiradeveloper]

done.