* This information includes the last known current term of the RaftActor - * and which peer was voted for by the RaftActor in that term + * and which candidate was voted for by the RaftActor in that term. + * *
- * This class ensures that election term information is persisted + * This class ensures that election term information is persisted. */ public interface ElectionTerm { /** - * latest term server has seen (initialized to 0 - * on first boot, increases monotonically) + * Returns the current leader's Raft term. + * + * @return the current leader's Raft term. */ long getCurrentTerm(); /** - * candidateId that received vote in current - * term (or null if none) + * Returns the id of the candidate that this server voted for in current term. + * + * @return candidate id that received the vote or null if no candidate was voted for. */ + @Nullable String getVotedFor(); /** - * To be called mainly when we are recovering in-memory election state from - * persistent storage + * This method updates the in-memory election term state. This method should be called when recovering election + * state from persistent storage. * - * @param currentTerm - * @param votedFor + * @param term the election term. + * @param votedFor the candidate id that was voted for. */ - void update(long currentTerm, String votedFor); + void update(long term, @Nullable String votedFor); /** - * To be called when we need to update the current term either because we - * received a message from someone with a more up-to-date term or because we - * just voted for someone - *
- * This information needs to be persisted so that on recovery the replica - * can start itself in the right term and know if it has already voted in - * that term or not + * This method updates the in-memory election term state and persists it so it can be recovered on next restart. + * This method should be called when starting a new election or when a Raft RPC message is received with a higher + * term. * - * @param currentTerm - * @param votedFor + * @param term the election term. + * @param votedFor the candidate id that was voted for. */ - void updateAndPersist(long currentTerm, String votedFor); + void updateAndPersist(long term, @Nullable String votedFor); }