[tarantool-patches] [PATCH 5/5] Disallow lsn gaps while vclock following

[Georgy Kirichenko <georgy@tarantool.org>]

Only one-step vclock following is allowed. This enforces wal and
replication consistency against out of order execution.

Needed for: #980
---
 src/box/replication.cc |  1 +
 src/box/vclock.c       |  2 +-
 src/box/xrow.c         |  2 +-
 test/unit/vclock.cc    | 10 +++++-----
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/box/replication.cc b/src/box/replication.cc
index 51e08886c..ee92a941b 100644
--- a/src/box/replication.cc
+++ b/src/box/replication.cc
@@ -91,6 +91,7 @@ replication_init(void)
 	replicaset.replica_by_id = (struct replica **)calloc(VCLOCK_MAX, sizeof(struct replica *));
 	latch_create(&replicaset.applier.order_latch);
 	vclock_create(&replicaset.applier.vclock);
+	vclock_clear(&replicaset.applier.vclock);
 }
 
 void
diff --git a/src/box/vclock.c b/src/box/vclock.c
index c297d1ff9..807da9109 100644
--- a/src/box/vclock.c
+++ b/src/box/vclock.c
@@ -56,7 +56,7 @@ vclock_follow(struct vclock *vclock, uint32_t replica_id, int64_t lsn)
 	assert(lsn >= 0);
 	assert(replica_id < VCLOCK_MAX);
 	int64_t prev_lsn = vclock->lsn[replica_id];
-	assert(lsn > prev_lsn);
+	assert(lsn == prev_lsn + 1);
 	/* Easier add each time than check. */
 	vclock->map |= 1 << replica_id;
 	vclock->lsn[replica_id] = lsn;
diff --git a/src/box/xrow.c b/src/box/xrow.c
index 67019a68d..ef3f81add 100644
--- a/src/box/xrow.c
+++ b/src/box/xrow.c
@@ -83,7 +83,7 @@ mp_decode_vclock(const char **data, struct vclock *vclock)
 			return -1;
 		int64_t lsn = mp_decode_uint(data);
 		if (lsn > 0)
-			vclock_follow(vclock, id, lsn);
+			vclock_set(vclock, id, lsn);
 	}
 	return 0;
 }
diff --git a/test/unit/vclock.cc b/test/unit/vclock.cc
index 8498eba3b..6a8d498ef 100644
--- a/test/unit/vclock.cc
+++ b/test/unit/vclock.cc
@@ -50,11 +50,11 @@ test_compare_one(uint32_t a_count, const int64_t *lsns_a,
 	vclock_create(&b);
 	for (uint32_t node_id = 0; node_id < a_count; node_id++) {
 		if (lsns_a[node_id] > 0)
-			vclock_follow(&a, node_id, lsns_a[node_id]);
+			vclock_set(&a, node_id, lsns_a[node_id]);
 	}
 	for (uint32_t node_id = 0; node_id < b_count; node_id++) {
 		if (lsns_b[node_id] > 0)
-			vclock_follow(&b, node_id, lsns_b[node_id]);
+			vclock_set(&b, node_id, lsns_b[node_id]);
 	}
 
 	return vclock_compare(&a, &b);
@@ -119,7 +119,7 @@ testset_create(vclockset_t *set, int64_t *files, int files_n, int node_n)
 			signature += lsn;
 
 			/* Update cluster hash */
-			vclock_follow(vclock, node_id, lsn);
+			vclock_set(vclock, node_id, lsn);
 		}
 		vclockset_insert(set, vclock);
 	}
@@ -225,7 +225,7 @@ test_isearch()
 			if (lsn <= 0)
 				continue;
 
-			vclock_follow(&vclock, node_id, lsn);
+			vclock_set(&vclock, node_id, lsn);
 		}
 
 		int64_t check = *(query + NODE_N);
@@ -247,7 +247,7 @@ test_tostring_one(uint32_t count, const int64_t *lsns, const char *res)
 	vclock_create(&vclock);
 	for (uint32_t node_id = 0; node_id < count; node_id++) {
 		if (lsns[node_id] > 0)
-			vclock_follow(&vclock, node_id, lsns[node_id]);
+			vclock_set(&vclock, node_id, lsns[node_id]);
 	}
 	char *str = vclock_to_string(&vclock);
 	int result = strcmp(str, res);
-- 
2.20.1