raft: re-add support for pre-vote in RaftTalker

src/raft/RaftTalker.cc

@@ -203,10 +203,16 @@ std::future<redisReplyPtr> RaftTalker::appendEntries(
   return qcl->execute(payload);
 }
 
-std::future<redisReplyPtr> RaftTalker::requestVote(const RaftVoteRequest &req) {
+std::future<redisReplyPtr> RaftTalker::requestVote(const RaftVoteRequest &req, bool preVote) {
   RedisRequest payload;
 
-  payload.emplace_back("RAFT_REQUEST_VOTE");
+  if(preVote) {
+    payload.emplace_back("RAFT_REQUEST_PRE_VOTE");
+  }
+  else {
+    payload.emplace_back("RAFT_REQUEST_VOTE");
+  }
+
   payload.emplace_back(std::to_string(req.term));
   payload.emplace_back(req.candidate.toString());
   payload.emplace_back(std::to_string(req.lastIndex));

src/raft/RaftTalker.hh

@@ -47,7 +47,7 @@ public:
                                            RaftTerm prevTerm, LogIndex commit,
                                            const std::vector<RaftSerializedEntry> &entries);
 
-  std::future<redisReplyPtr> requestVote(const RaftVoteRequest &req);
+  std::future<redisReplyPtr> requestVote(const RaftVoteRequest &req, bool preVote = false);
   std::future<redisReplyPtr> fetch(LogIndex index);
 
   std::future<redisReplyPtr> resilveringStart(const ResilveringEventID &id);