quorum_set/quorum/
quorum_bridge_impl.rs

1use std::collections::BTreeSet;
2
3use crate::quorum::QuorumBridge;
4use crate::quorum::QuorumIntersection;
5
6/// Builds an intermediate joint quorum set for a target flat config.
7///
8/// The result is the target alone when [`QuorumIntersection::intersects_with`] proves that every
9/// quorum of `self` intersects every quorum of the target, e.g. when the target adds one voter to
10/// a uniform `self`. Otherwise it is the joint of the last config of `self` and the target.
11///
12/// A Raft-style caller that applies a target-alone result must first commit an entry of the
13/// leader's own term. Otherwise two leaders of different terms can each move from the same
14/// committed config to a different target, and the two targets can have disjoint quorums.
15impl<ID> QuorumBridge<BTreeSet<ID>> for Vec<BTreeSet<ID>>
16where ID: Ord + Clone
17{
18    fn bridge_to(&self, other: BTreeSet<ID>) -> Self {
19        let intersects = self.intersects_with(&other);
20        if intersects == Some(true) {
21            vec![other]
22        } else if let Some(last) = self.last() {
23            vec![last.clone(), other]
24        } else {
25            vec![other]
26        }
27    }
28}
29
30/// Builds an intermediate joint quorum set for a target joint config.
31///
32/// The result is the target alone when [`QuorumIntersection::intersects_with`] proves that every
33/// quorum of `self` intersects every quorum of the target. Otherwise it is the joint of the last
34/// config of `self` and the configs of the target. For a target that holds one config, the result
35/// equals the result for that config as a [`BTreeSet`] target.
36///
37/// A Raft-style caller that applies a target-alone result must first commit an entry of the
38/// leader's own term. Otherwise two leaders of different terms can each move from the same
39/// committed config to a different target, and the two targets can have disjoint quorums.
40impl<ID> QuorumBridge<Vec<BTreeSet<ID>>> for Vec<BTreeSet<ID>>
41where ID: Ord + Clone
42{
43    fn bridge_to(&self, other: Vec<BTreeSet<ID>>) -> Self {
44        let intersects = self.intersects_with(&other);
45        if intersects == Some(true) {
46            other
47        } else if let Some(last) = self.last() {
48            let mut joint = vec![last.clone()];
49            joint.extend(other);
50            joint
51        } else {
52            other
53        }
54    }
55}
quorum_set/quorum/quorum_bridge_impl.rs

quorum_set/quorum/
quorum_bridge_impl.rs
