Enum Role 

pub enum Role {
    Unattached {
        election_deadline: SimInstant,
    },
    Voted {
        election_deadline: SimInstant,
    },
    Follower {
        leader_id: NodeId,
        fetch_deadline: SimInstant,
        has_fetched_from_leader: bool,
    },
    Prospective {
        granted: BTreeSet<NodeId>,
        rejected: BTreeSet<NodeId>,
        election_deadline: SimInstant,
        abandoned_leader: Option<NodeId>,
    },
    Candidate {
        granted: BTreeSet<NodeId>,
        election_deadline: SimInstant,
    },
    Leader {
        replicas: BTreeMap<NodeId, ReplicaProgress>,
        fetched_voters: BTreeSet<NodeId>,
        high_watermark: i64,
        epoch_start_offset: i64,
    },
    Resigned,
    Observer {
        leader_id: Option<NodeId>,
        fetch_deadline: SimInstant,
    },
}

Variants

Unattached

Knows the epoch, no leader yet. May hold a non-binding pre-vote grant.

Fields

election_deadline: SimInstant

Voted

Cast a binding vote this epoch; now waits for a leader.

Fields

election_deadline: SimInstant

Follower

Has a leader for the epoch and fetches from it.

Fields

leader_id: NodeId

fetch_deadline: SimInstant

has_fetched_from_leader: bool

Whether a Fetch to leader_id has been answered successfully since this replica began following it: Kafka’s FollowerState.hasFetchedFromLeader. Until then the leader may be unreachable from here, so the follower grants a pre-vote.

Prospective

KIP-996 pre-vote candidate that collects non-binding grants.

Fields

granted: BTreeSet<NodeId>

rejected: BTreeSet<NodeId>

The voters that refused the pre-vote. Kafka’s EpochElection records them so that the round ends as soon as it can no longer win.

election_deadline: SimInstant

abandoned_leader: Option<NodeId>

The leader of this epoch that the replica gave up on when it began the round, if it had one. Kafka’s ProspectiveState keeps the leaderId of the FollowerState it came from, and a replica that knows a leader for its epoch grants no binding vote in it. QuorumState::leader_id is None meanwhile, so that the replica still attaches to a leader announced at this epoch.

Candidate

Real candidacy: the epoch is bumped and the replica voted for itself.

Fields

granted: BTreeSet<NodeId>

election_deadline: SimInstant

Leader

Won the election; tracks follower progress for HWM.

Fields

replicas: BTreeMap<NodeId, ReplicaProgress>

fetched_voters: BTreeSet<NodeId>

Voters that have fetched inside the current check-quorum window.

This is Kafka’s LeaderState.fetchedVoters: it never contains the leader itself, and it is emptied — and the check-quorum timer re-armed — the moment it reaches the majority the leader needs besides its own vote. A leader that reaches the deadline with the set still short of that count has lost the quorum and resigns.

high_watermark: i64

epoch_start_offset: i64

Log end offset at the moment of promotion, that is, where this leader’s LeaderChange record sits. That record is the first current-epoch record.

The HWM may only advance past this offset. This enforces Raft Fig.8 leader completeness: a current-epoch entry must be majority-replicated before commit.

Resigned

Stepped down: told the voters to elect, and waits for its own election timer to start a pre-vote round.

A leader reaches this variant when its check-quorum window expires. It no longer serves Fetch, no longer advances the high watermark, and no longer claims the leadership in QuorumState, so an isolated old leader stops answering as leader for its epoch.

Observer

Not in the voter set; only ever fetches.

Fields

leader_id: Option<NodeId>

fetch_deadline: SimInstant

Implementations

impl Role

pub const fn name(&self) -> &'static str

The text this variant stands for.

impl Role

pub fn is_leader(&self) -> bool

Trait Implementations

impl Clone for Role

fn clone(&self) -> Role

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Role

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Role

fn default() -> Self

Returns the “default value” for a type.

impl Eq for Role

impl Hash for Role

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Role

fn eq(&self, other: &Role) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Role