Re: [Tarantool-patches] [PATCH v2 09/11] raft: introduce state machine

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

And my new changes on top of it, in a separate commit.

====================

diff --git a/src/box/applier.cc b/src/box/applier.cc
index c352faf5e..10186ab91 100644
--- a/src/box/applier.cc
+++ b/src/box/applier.cc
@@ -885,6 +885,11 @@ static int
 applier_handle_raft(struct applier *applier, struct xrow_header *row)
 {
 	assert(iproto_type_is_raft_request(row->type));
+	if (applier->instance_id == 0) {
+		diag_set(ClientError, ER_PROTOCOL, "Can't apply a Raft request "
+			 "from an instance without an ID");
+		return -1;
+	}
 
 	struct raft_request req;
 	struct vclock candidate_clock;
diff --git a/src/box/raft.c b/src/box/raft.c
index 07a49351f..b3ab94bd7 100644
--- a/src/box/raft.c
+++ b/src/box/raft.c
@@ -347,6 +347,7 @@ raft_process_msg(const struct raft_request *req, uint32_t source)
 	if (req->vote != 0) {
 		switch (raft.state) {
 		case RAFT_STATE_FOLLOWER:
+		case RAFT_STATE_LEADER:
 			/*
 			 * Can't respond on vote requests when Raft is disabled.
 			 */
@@ -386,6 +387,12 @@ raft_process_msg(const struct raft_request *req, uint32_t source)
 					 "indirect votes are not allowed");
 				break;
 			}
+			if (raft.leader != 0) {
+				say_info("RAFT: vote request is skipped - the "
+					 "leader is already known - %u",
+					 raft.leader);
+				break;
+			}
 			/*
 			 * Either the term is new, or didn't vote in the current
 			 * term yet. Anyway can vote now.
@@ -415,16 +422,6 @@ raft_process_msg(const struct raft_request *req, uint32_t source)
 			}
 			raft_sm_become_leader();
 			break;
-		case RAFT_STATE_LEADER:
-			/*
-			 * If the node is still a leader, it ignores all votes.
-			 * Indeed, if the received vote would be from a new
-			 * term, the node would bump its own term and would
-			 * enter the follower state by now. If the vote is from
-			 * the current term, then the leader can freely ignore
-			 * it.
-			 */
-			break;
 		default:
 			unreachable();
 		}
@@ -466,6 +463,12 @@ end:
 void
 raft_process_heartbeat(uint32_t source)
 {
+	/*
+	 * Raft handles heartbeats from all instances, including anon instances
+	 * which don't participate in Raft.
+	 */
+	if (source == 0)
+		return;
 	/*
 	 * When not a candidate - don't wait for anything. Therefore do not care
 	 * about the leader being dead.
@@ -746,6 +749,7 @@ raft_sm_schedule_new_vote(uint32_t new_vote)
 {
 	say_info("RAFT: vote for %u, follow", new_vote, raft.volatile_term);
 	assert(raft.volatile_vote == 0);
+	assert(raft.leader == 0);
 	assert(raft.state == RAFT_STATE_FOLLOWER);
 	raft.volatile_vote = new_vote;
 	raft_sm_pause_and_dump();
@@ -929,15 +933,8 @@ raft_cfg_election_quorum(void)
 		return;
 	if (raft.vote_count < raft_election_quorum())
 		return;
-	/*
-	 * The node is a candidate. It means its state if fully synced with
-	 * disk. Otherwise it would be a follower.
-	 */
-	assert(!raft.is_write_in_progress);
-	raft.state = RAFT_STATE_LEADER;
-	raft.leader = instance_id;
+	raft_sm_become_leader();
 	raft_broadcast_new_state();
-	box_update_ro_summary();
 }
 
 void