LGTM.
 
 
Четверг, 20 августа 2020, 0:35 +03:00 от Cyrill Gorcunov <gorcunov@gmail.com>:
 
These msgpack entries will be needed to write them
down to a journal without involving txn engine. Same
time we would like to be able to allocate them on stack,
for this sake the binary form is predefined.

Part-of #5129

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 src/box/txn_limbo.c | 9 +++++++--
 src/box/xrow.c | 41 ++++++++++++++++++-----------------------
 src/box/xrow.h | 20 +++++++++++++++-----
 3 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index c6a4e5efc..e458dad75 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -283,6 +283,11 @@ txn_limbo_write_synchro(struct txn_limbo *limbo, uint32_t type, int64_t lsn)
  .lsn = lsn,
  };
 
+ /*
+ * This is a synchronous commit so we can
+ * use body and row allocated on a stack.
+ */
+ struct synchro_body_bin body;
  struct xrow_header row;
  struct request request = {
  .header = &row,
@@ -292,8 +297,8 @@ txn_limbo_write_synchro(struct txn_limbo *limbo, uint32_t type, int64_t lsn)
  if (txn == NULL)
  goto rollback;
 
- if (xrow_encode_synchro(&row, &txn->region, &req) != 0)
- goto rollback;
+ xrow_encode_synchro(&row, &body, &req);
+
  /*
  * This is not really a transaction. It just uses txn API
  * to put the data into WAL. And obviously it should not
diff --git a/src/box/xrow.c b/src/box/xrow.c
index bf174c701..9c6fb4fc1 100644
--- a/src/box/xrow.c
+++ b/src/box/xrow.c
@@ -893,35 +893,30 @@ xrow_encode_dml(const struct request *request, struct region *region,
  return iovcnt;
 }
 
-int
-xrow_encode_synchro(struct xrow_header *row, struct region *region,
+void
+xrow_encode_synchro(struct xrow_header *row,
+ struct synchro_body_bin *body,
  const struct synchro_request *req)
 {
- size_t len = mp_sizeof_map(2) + mp_sizeof_uint(IPROTO_REPLICA_ID) +
- mp_sizeof_uint(req->replica_id) +
- mp_sizeof_uint(IPROTO_LSN) + mp_sizeof_uint(req->lsn);
- char *buf = (char *)region_alloc(region, len);
- if (buf == NULL) {
- diag_set(OutOfMemory, len, "region_alloc", "buf");
- return -1;
- }
- char *pos = buf;
-
- pos = mp_encode_map(pos, 2);
- pos = mp_encode_uint(pos, IPROTO_REPLICA_ID);
- pos = mp_encode_uint(pos, req->replica_id);
- pos = mp_encode_uint(pos, IPROTO_LSN);
- pos = mp_encode_uint(pos, req->lsn);
+ /*
+ * A map with two elements. We don't compress
+ * numbers to have this structure constant in size,
+ * which allows us to preallocate it on stack.
+ */
+ body->m_body = 0x80 | 2;
+ body->k_replica_id = IPROTO_REPLICA_ID;
+ body->m_replica_id = 0xce;
+ body->v_replica_id = mp_bswap_u32(req->replica_id);
+ body->k_lsn = IPROTO_LSN;
+ body->m_lsn = 0xcf;
+ body->v_lsn = mp_bswap_u64(req->lsn);
 
  memset(row, 0, sizeof(*row));
 
- row->body[0].iov_base = buf;
- row->body[0].iov_len = len;
- row->bodycnt = 1;
-
  row->type = req->type;
-
- return 0;
+ row->body[0].iov_base = (void *)body;
+ row->body[0].iov_len = sizeof(*body);
+ row->bodycnt = 1;
 }
 
 int
diff --git a/src/box/xrow.h b/src/box/xrow.h
index 02dca74e5..20e82034d 100644
--- a/src/box/xrow.h
+++ b/src/box/xrow.h
@@ -240,16 +240,26 @@ struct synchro_request {
  int64_t lsn;
 };
 
+/** Synchro request xrow's body in MsgPack format. */
+struct PACKED synchro_body_bin {
+ uint8_t m_body;
+ uint8_t k_replica_id;
+ uint8_t m_replica_id;
+ uint32_t v_replica_id;
+ uint8_t k_lsn;
+ uint8_t m_lsn;
+ uint64_t v_lsn;
+};
+
 /**
  * Encode synchronous replication request.
  * @param row xrow header.
- * @param region Region to use to encode the confirmation body.
+ * @param body Desination to use to encode the confirmation body.
  * @param req Request parameters.
- * @retval -1 on error.
- * @retval 0 success.
  */
-int
-xrow_encode_synchro(struct xrow_header *row, struct region *region,
+void
+xrow_encode_synchro(struct xrow_header *row,
+ struct synchro_body_bin *body,
  const struct synchro_request *req);
 
 /**
--
2.26.2
 
--
Serge Petrenko