[Tarantool-patches] [PATCH 5/7] replication: send latest effective promote in initial join

[Serge Petrenko via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

A joining instance may never receive the latest PROMOTE request, which
is the only source of information about the limbo owner. Send out the
latest limbo state (e.g. the latest applied PROMOTE request) together
with the initial join snapshot.

Part-of #6034
---
 src/box/applier.cc |  5 +++++
 src/box/relay.cc   | 10 ++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/box/applier.cc b/src/box/applier.cc
index 33181fdbf..dde045996 100644
--- a/src/box/applier.cc
+++ b/src/box/applier.cc
@@ -458,6 +458,11 @@ applier_wait_snapshot(struct applier *applier)
 				xrow_decode_vclock_xc(&row, &replicaset.vclock);
 			}
 			break; /* end of stream */
+		} else if (iproto_type_is_promote_request(row.type)) {
+			struct synchro_request req;
+			if (xrow_decode_synchro(&row, &req) != 0)
+				diag_raise();
+			txn_limbo_process(&txn_limbo, &req);
 		} else if (iproto_type_is_error(row.type)) {
 			xrow_decode_error_xc(&row);  /* rethrow error */
 		} else {
diff --git a/src/box/relay.cc b/src/box/relay.cc
index b1571b361..2781b2c22 100644
--- a/src/box/relay.cc
+++ b/src/box/relay.cc
@@ -399,12 +399,22 @@ relay_initial_join(int fd, uint64_t sync, struct vclock *vclock)
 	if (txn_limbo_wait_confirm(&txn_limbo) != 0)
 		diag_raise();
 
+	struct synchro_request req;
+	txn_limbo_checkpoint(&txn_limbo, &req);
+
 	/* Respond to the JOIN request with the current vclock. */
 	struct xrow_header row;
 	xrow_encode_vclock_xc(&row, vclock);
 	row.sync = sync;
 	coio_write_xrow(&relay->io, &row);
 
+	/* Send out the latest limbo state. */
+	char body[XROW_SYNCHRO_BODY_LEN_MAX];
+	xrow_encode_synchro(&row, body, &req);
+	row.replica_id = req.replica_id;
+	row.sync = sync;
+	coio_write_xrow(&relay->io, &row);
+
 	/* Send read view to the replica. */
 	engine_join_xc(&ctx, &relay->stream);
 }
-- 
2.30.1 (Apple Git-130)