nodedb_cluster/multi_raft/
membership.rs

1// SPDX-License-Identifier: BUSL-1.1
2
3//! Group-level membership helpers consumed by the tick loop's join /
4//! promotion phases.
5//!
6//! - `commit_index_for(group)`: used by the join flow to wait until a
7//!   proposed `AddLearner` conf-change commits before replying to the
8//!   joining node.
9//! - `ready_learners(group)`: used by the tick loop's "promote
10//!   caught-up learners" phase — returns every learner in the group
11//!   whose `match_index` on this (leader) node is at least the current
12//!   `commit_index`, i.e. learners that have replicated enough log to be
13//!   safely promoted.
14//! - `group_leader(group)`: leader id observed by this node's local
15//!   RaftNode state, used by the join flow to decide redirect vs admit.
16//! - `group_role_is_leader(group)`: cheap leader-check helper.
17
18use nodedb_raft::NodeRole;
19
20use super::core::MultiRaft;
21
22impl MultiRaft {
23    /// Current commit index for a group, or `None` if the group is not
24    /// hosted on this node.
25    pub fn commit_index_for(&self, group_id: u64) -> Option<u64> {
26        self.groups.get(&group_id).map(|n| n.commit_index())
27    }
28
29    /// Learners in `group_id` whose `match_index` on this leader has
30    /// caught up to the current `commit_index` — safe to promote.
31    ///
32    /// Returns an empty vec if this node is not the leader of the group
33    /// or the group is not hosted here.
34    pub fn ready_learners(&self, group_id: u64) -> Vec<u64> {
35        let Some(node) = self.groups.get(&group_id) else {
36            return Vec::new();
37        };
38        if node.role() != NodeRole::Leader {
39            return Vec::new();
40        }
41        let commit = node.commit_index();
42        node.learners()
43            .iter()
44            .copied()
45            .filter(|&learner| node.match_index_for(learner).unwrap_or(0) >= commit)
46            .collect()
47    }
48
49    /// Observed leader id for a group (0 = unknown / no election yet).
50    pub fn group_leader(&self, group_id: u64) -> u64 {
51        self.groups
52            .get(&group_id)
53            .map(|n| n.leader_id())
54            .unwrap_or(0)
55    }
56
57    /// Whether this node is currently the leader of `group_id`.
58    pub fn group_role_is_leader(&self, group_id: u64) -> bool {
59        self.groups
60            .get(&group_id)
61            .map(|n| n.role() == NodeRole::Leader)
62            .unwrap_or(false)
63    }
64}
nodedb_cluster/multi_raft/membership.rs

nodedb_cluster/multi_raft/
membership.rs
