Struct WitnessSupervisor 

pub struct WitnessSupervisor<S>
where
    S: LastVoteStore,
{ /* private fields */ }

A booted witness node: the control-plane supervisor with no data plane.

A witness is a Voter over a durable last-vote store plus the node’s shared NodeIdentity — and nothing else. There is intentionally no engine, no WAL, and no replication handle on this struct: a witness cannot serve data because it holds none.

The store type is generic so production uses the durable FileLastVoteStore (ADR 0030: “the supervisor needs durable per-node vote state to prevent double-voting across restarts”) while tests use an in-memory store.

Implementations

impl<S> WitnessSupervisor<S>

where S: LastVoteStore,

pub fn new(identity: NodeIdentity, store: S) -> WitnessSupervisor<S>

Boot a witness supervisor over store, identified by the shared per-node identity. The voter id is the identity’s certificate subject, so the witness votes under the same identity a data member would replicate under.

pub fn profile(&self) -> RuntimeProfile

A witness always runs the witness profile.

pub fn boots_data_plane(&self) -> bool

A witness never boots a data plane — invariant by construction, stated here so callers (and the boot pipeline) can assert it without reaching into the profile.

pub fn identity(&self) -> &NodeIdentity

The shared per-node identity this witness authenticates with — the same NodeIdentity type a data member presents over mTLS.

pub fn member(&self) -> Member

This witness’s entry in the supervisor’s membership view: a vote-only MemberKind::Witness, always VotingState::Voting. It counts toward quorum but is never electable.

pub fn consider_vote( &self, req: &VoteRequest, commit_watermark: u64, ) -> Result<VoteDecision, LastVoteError>

Consider a candidate’s vote request against the current commit watermark — the only control-plane action a witness performs. The watermark rule and the durable double-vote guard live in the Voter, so a witness applies the exact same safety rule a data voter does.

pub fn current_term(&self) -> Result<u64, LastVoteError>

The highest term this witness has durably recorded.

impl WitnessSupervisor<FileLastVoteStore>

pub fn with_durable_store( identity: NodeIdentity, last_vote_path: impl Into<PathBuf>, ) -> WitnessSupervisor<FileLastVoteStore>

Boot a witness with a durable, on-disk last-vote store at last_vote_path — the production constructor. Survives a restart so a witness that crashes mid-term never double-votes (ADR 0030).