[Tarantool-patches] [PATCH v2 06/16] raft: make raft_request.vclock constant

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

Raft is never supposed to change vclock. Not the stored one, nor
the received ones. The patch makes it checked during compilation.

The patch is mostly motivated by a next patch making Raft use an
externally configured vclock which can't be changed. Since Raft
uses raft_request to carry the vclock in a few places, the
request's vclock also must become const.

Part of #5303
---
 src/box/box.cc    | 2 +-
 src/box/raftlib.c | 9 +++------
 src/box/raftlib.h | 3 +--
 src/box/xrow.c    | 2 +-
 src/box/xrow.h    | 2 +-
 5 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/src/box/box.cc b/src/box/box.cc
index e8e232126..043a37658 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -2142,7 +2142,7 @@ box_process_subscribe(struct ev_io *io, struct xrow_header *header)
 		 * should be 0.
 		 */
 		struct raft_request req;
-		raft_serialize_for_network(box_raft(), &req, &vclock);
+		raft_serialize_for_network(box_raft(), &req);
 		xrow_encode_raft(&row, &fiber()->gc, &req);
 		coio_write_xrow(io, &row);
 	}
diff --git a/src/box/raftlib.c b/src/box/raftlib.c
index ca1940ba6..78164bf91 100644
--- a/src/box/raftlib.c
+++ b/src/box/raftlib.c
@@ -850,8 +850,7 @@ raft_sm_stop(struct raft *raft)
 }
 
 void
-raft_serialize_for_network(const struct raft *raft, struct raft_request *req,
-			   struct vclock *vclock)
+raft_serialize_for_network(const struct raft *raft, struct raft_request *req)
 {
 	memset(req, 0, sizeof(*req));
 	/*
@@ -865,10 +864,8 @@ raft_serialize_for_network(const struct raft *raft, struct raft_request *req,
 	 * Raft does not own vclock, so it always expects it passed externally.
 	 * Vclock is sent out only by candidate instances.
 	 */
-	if (req->state == RAFT_STATE_CANDIDATE) {
-		req->vclock = vclock;
-		vclock_copy(vclock, &replicaset.vclock);
-	}
+	if (req->state == RAFT_STATE_CANDIDATE)
+		req->vclock = &replicaset.vclock;
 }
 
 void
diff --git a/src/box/raftlib.h b/src/box/raftlib.h
index f75ed2567..2da3cec86 100644
--- a/src/box/raftlib.h
+++ b/src/box/raftlib.h
@@ -263,8 +263,7 @@ raft_new_term(struct raft *raft);
  * cluster. It is allowed to save anything here, not only persistent state.
  */
 void
-raft_serialize_for_network(const struct raft *raft, struct raft_request *req,
-			   struct vclock *vclock);
+raft_serialize_for_network(const struct raft *raft, struct raft_request *req);
 
 /**
  * Save complete Raft state into a request to be persisted on disk. Only term
diff --git a/src/box/xrow.c b/src/box/xrow.c
index 165a00a16..bc06738ad 100644
--- a/src/box/xrow.c
+++ b/src/box/xrow.c
@@ -1057,7 +1057,7 @@ xrow_decode_raft(const struct xrow_header *row, struct raft_request *r,
 			r->vclock = vclock;
 			if (r->vclock == NULL)
 				mp_next(&pos);
-			else if (mp_decode_vclock_ignore0(&pos, r->vclock) != 0)
+			else if (mp_decode_vclock_ignore0(&pos, vclock) != 0)
 				goto bad_msgpack;
 			break;
 		default:
diff --git a/src/box/xrow.h b/src/box/xrow.h
index 095911239..3d68c1268 100644
--- a/src/box/xrow.h
+++ b/src/box/xrow.h
@@ -268,7 +268,7 @@ struct raft_request {
 	uint64_t term;
 	uint32_t vote;
 	uint32_t state;
-	struct vclock *vclock;
+	const struct vclock *vclock;
 };
 
 int
-- 
2.24.3 (Apple Git-128)