databendlabs / openraft / 27423417226

87%

Build Type

push

github

Committed by drmingdrmer

Commit Message

feat: add Pre-Vote to avoid disruptive term inflation

# Summary

A follower probes whether a quorum would grant its vote at the next term
before persisting a vote or bumping its term, so a node that cannot
currently win -- partitioned, restarted, or with a stale log -- does not
inflate the cluster term and disrupt a healthy leader on reconnect.

# Details

- Config::enable_pre_vote: Option<bool> gates the automatic round on election
  timeout. None, the default, is treated as disabled, leaving room to change
  the default later without breaking existing configs.

- Trigger::elect now takes pre_vote: bool, so an operator can run a cautious
  manual election independent of the config; existing callers pass false.

- New RaftNetworkV2::pre_vote RPC. The default impl grants unconditionally so
  a cluster mid-upgrade stays live, and a transport error is never counted as
  a grant, so an isolated node cannot synthesize a quorum.

- Engine pre_elect / handle_pre_vote_req / handle_pre_vote_resp run the round
  without persisting a vote or changing server state; a would-grant quorum
  starts the real election, and a real election or a higher accepted vote
  supersedes an in-flight round.

- Fix: #1770

Coverage Stats

220 of 244 new or added lines in 20 files covered. (90.16%)

7 existing lines in 3 files now uncovered.

16702 of 19281 relevant lines covered (86.62%)

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