[tarantool-patches] [PATCH 04/10] Get rid of autocommit from a txn structure

[Georgy Kirichenko <georgy@tarantool.org>]

Move transaction auto start and auto commit behavior to the box level.
From now a transaction won't start and commit automatically without
txn_begin/txn_commit invocations. This is a part of a bigger transaction
refactoring in order to implement detachable transactions and a parallel
applier.

Prerequisites: #1254
---
 src/box/applier.cc     | 27 ++++++++++++---
 src/box/box.cc         | 76 +++++++++++++++++++++++++++++++-----------
 src/box/memtx_engine.c | 10 ++++--
 src/box/txn.c          | 25 ++++----------
 src/box/txn.h          |  7 +---
 src/box/vinyl.c        | 12 +++----
 6 files changed, 99 insertions(+), 58 deletions(-)

diff --git a/src/box/applier.cc b/src/box/applier.cc
index 373e1feb9..3b74e0f54 100644
--- a/src/box/applier.cc
+++ b/src/box/applier.cc
@@ -172,11 +172,22 @@ applier_writer_f(va_list ap)
 static int
 apply_initial_join_row(struct xrow_header *row)
 {
+	struct txn *txn = txn_begin();
+	if (txn == NULL)
+		return -1;
 	struct request request;
 	xrow_decode_dml(row, &request, dml_request_key_map(row->type));
-	struct space *space = space_cache_find_xc(request.space_id);
+	struct space *space = space_cache_find(request.space_id);
+	if (space == NULL)
+		return -1;
 	/* no access checks here - applier always works with admin privs */
-	return space_apply_initial_join_row(space, &request);
+	if (space_apply_initial_join_row(space, &request)) {
+		txn_rollback();
+		return -1;
+	}
+	int rc = txn_commit(txn);
+	fiber_gc();
+	return rc;
 }
 
 /**
@@ -403,8 +414,16 @@ applier_join(struct applier *applier)
 		applier->last_row_time = ev_monotonic_now(loop());
 		if (iproto_type_is_dml(row.type)) {
 			vclock_follow_xrow(&replicaset.vclock, &row);
-			if (apply_row(&row) != 0)
+			struct txn *txn = txn_begin();
+			if (txn == NULL)
+				diag_raise();
+			if (apply_row(&row) != 0) {
+				txn_rollback();
+				diag_raise();
+			}
+			if (txn_commit(txn) != 0)
 				diag_raise();
+			fiber_gc();
 			if (++row_count % 100000 == 0)
 				say_info("%.1fM rows received", row_count / 1e6);
 		} else if (row.type == IPROTO_OK) {
@@ -555,7 +574,7 @@ applier_apply_tx(struct stailq *rows)
 	 * conflict safely access failed xrow object and allocate
 	 * IPROTO_NOP on gc.
 	 */
-	struct txn *txn = txn_begin(false);
+	struct txn *txn = txn_begin();
 	struct applier_tx_row *item;
 	if (txn == NULL)
 		diag_raise();
diff --git a/src/box/box.cc b/src/box/box.cc
index 7828f575b..54210474f 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -169,34 +169,54 @@ int
 box_process_rw(struct request *request, struct space *space,
 	       struct tuple **result)
 {
+	struct tuple *tuple = NULL;
+	struct txn *txn = in_txn();
+	bool autocommit = txn == NULL;
+	if (txn == NULL && (txn = txn_begin()) == NULL)
+		return -1;
 	assert(iproto_type_is_dml(request->type));
 	rmean_collect(rmean_box, request->type, 1);
 	if (access_check_space(space, PRIV_W) != 0)
-		return -1;
-	struct txn *txn = txn_begin_stmt(space);
-	if (txn == NULL)
-		return -1;
-	struct tuple *tuple;
+		goto fail;
+	if (txn_begin_stmt(space) == NULL)
+		goto fail;
 	if (space_execute_dml(space, txn, request, &tuple) != 0) {
 		txn_rollback_stmt();
-		return -1;
+		goto fail;
 	}
-	if (result == NULL)
-		return txn_commit_stmt(txn, request);
-	*result = tuple;
-	if (tuple == NULL)
-		return txn_commit_stmt(txn, request);
 	/*
 	 * Pin the tuple locally before the commit,
 	 * otherwise it may go away during yield in
 	 * when WAL is written in autocommit mode.
 	 */
-	tuple_ref(tuple);
-	int rc = txn_commit_stmt(txn, request);
-	if (rc == 0)
+	if (tuple != NULL)
+		tuple_ref(tuple);
+
+	if (result != NULL)
+		*result = tuple;
+
+	if (txn_commit_stmt(txn, request) != 0)
+		goto fail;
+	if (autocommit) {
+		if (txn_commit(txn) != 0)
+			goto fail;
+		fiber_gc();
+	}
+
+	if (tuple != NULL && result != NULL) {
 		tuple_bless(tuple);
-	tuple_unref(tuple);
-	return rc;
+	}
+
+	if (tuple != NULL)
+		tuple_unref(tuple);
+	return 0;
+
+fail:
+	if (autocommit)
+		txn_rollback();
+	if (tuple != NULL)
+		tuple_unref(tuple);
+	return -1;
 }
 
 void
@@ -299,8 +319,12 @@ apply_wal_row(struct xstream *stream, struct xrow_header *row)
 	xrow_decode_dml_xc(row, &request, dml_request_key_map(row->type));
 	if (request.type != IPROTO_NOP) {
 		struct space *space = space_cache_find_xc(request.space_id);
-		if (box_process_rw(&request, space, NULL) != 0) {
+		struct txn *txn = txn_begin();
+		if (txn == NULL || box_process_rw(&request, space, NULL) != 0 ||
+		    txn_commit(txn) != 0) {
 			say_error("error applying row: %s", request_str(&request));
+			if (txn != NULL)
+				txn_rollback();
 			diag_raise();
 		}
 	}
@@ -1313,8 +1337,15 @@ box_sequence_reset(uint32_t seq_id)
 static inline void
 box_register_replica(uint32_t id, const struct tt_uuid *uuid)
 {
+	struct txn *txn = txn_begin();
+	if (txn == NULL)
+		diag_raise();
 	if (boxk(IPROTO_INSERT, BOX_CLUSTER_ID, "[%u%s]",
-		 (unsigned) id, tt_uuid_str(uuid)) != 0)
+		 (unsigned) id, tt_uuid_str(uuid)) != 0) {
+		txn_rollback();
+		diag_raise();
+	}
+	if (txn_commit(txn) != 0)
 		diag_raise();
 	assert(replica_by_uuid(uuid)->id == id);
 }
@@ -1636,9 +1667,16 @@ box_set_replicaset_uuid(const struct tt_uuid *replicaset_uuid)
 		uu = *replicaset_uuid;
 	else
 		tt_uuid_create(&uu);
+	struct txn *txn = txn_begin();
+	if (txn == NULL)
+		diag_raise();
 	/* Save replica set UUID in _schema */
 	if (boxk(IPROTO_INSERT, BOX_SCHEMA_ID, "[%s%s]", "cluster",
-		 tt_uuid_str(&uu)))
+		 tt_uuid_str(&uu))) {
+		txn_rollback();
+		diag_raise();
+	}
+	if (txn_commit(txn) != 0)
 		diag_raise();
 }
 
diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
index 4d99910cb..afa1739c6 100644
--- a/src/box/memtx_engine.c
+++ b/src/box/memtx_engine.c
@@ -272,16 +272,22 @@ memtx_engine_recover_snapshot_row(struct memtx_engine *memtx,
 		diag_set(ClientError, ER_CROSS_ENGINE_TRANSACTION);
 		return -1;
 	}
+	struct txn *txn = txn_begin();
+	if (txn == NULL)
+		return -1;
 	/* no access checks here - applier always works with admin privs */
-	if (space_apply_initial_join_row(space, &request) != 0)
+	if (space_apply_initial_join_row(space, &request) != 0) {
+		txn_rollback();
 		return -1;
+	}
+	int rc = txn_commit(txn);
 	/*
 	 * Don't let gc pool grow too much. Yet to
 	 * it before reading the next row, to make
 	 * sure it's not freed along here.
 	 */
 	fiber_gc();
-	return 0;
+	return rc;
 }
 
 /** Called at start to tell memtx to recover to a given LSN. */
diff --git a/src/box/txn.c b/src/box/txn.c
index ffada5984..804962767 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -173,7 +173,7 @@ txn_free(struct txn *txn)
 }
 
 struct txn *
-txn_begin(bool is_autocommit)
+txn_begin()
 {
 	static int64_t tsn = 0;
 	assert(! in_txn());
@@ -186,7 +186,6 @@ txn_begin(bool is_autocommit)
 	txn->n_new_rows = 0;
 	txn->n_local_rows = 0;
 	txn->n_applier_rows = 0;
-	txn->is_autocommit = is_autocommit;
 	txn->has_triggers  = false;
 	txn->is_aborted = false;
 	txn->in_sub_stmt = 0;
@@ -224,19 +223,15 @@ txn_begin_stmt(struct space *space)
 {
 	struct txn *txn = in_txn();
 	if (txn == NULL) {
-		txn = txn_begin(true);
-		if (txn == NULL)
-			return NULL;
+		diag_set(ClientError, ER_NO_TRANSACTION);
+		return NULL;
 	} else if (txn->in_sub_stmt > TXN_SUB_STMT_MAX) {
 		diag_set(ClientError, ER_SUB_STMT_MAX);
 		return NULL;
 	}
 	struct txn_stmt *stmt = txn_stmt_new(txn);
-	if (stmt == NULL) {
-		if (txn->is_autocommit && txn->in_sub_stmt == 0)
-			txn_rollback();
+	if (stmt == NULL)
 		return NULL;
-	}
 	if (space == NULL)
 		return txn;
 
@@ -271,8 +266,7 @@ txn_is_distributed(struct txn *txn)
 }
 
 /**
- * End a statement. In autocommit mode, end
- * the current transaction as well.
+ * End a statement.
  */
 int
 txn_commit_stmt(struct txn *txn, struct request *request)
@@ -315,11 +309,6 @@ txn_commit_stmt(struct txn *txn, struct request *request)
 			goto fail;
 	}
 	--txn->in_sub_stmt;
-	if (txn->is_autocommit && txn->in_sub_stmt == 0) {
-		int rc = txn_commit(txn);
-		fiber_gc();
-		return rc;
-	}
 	return 0;
 fail:
 	txn_rollback_stmt();
@@ -446,8 +435,6 @@ txn_rollback_stmt()
 	if (txn == NULL || txn->in_sub_stmt == 0)
 		return;
 	txn->in_sub_stmt--;
-	if (txn->is_autocommit && txn->in_sub_stmt == 0)
-		return txn_rollback();
 	txn_rollback_to_svp(txn, txn->sub_stmt_begin[txn->in_sub_stmt]);
 }
 
@@ -518,7 +505,7 @@ box_txn_begin()
 		diag_set(ClientError, ER_ACTIVE_TRANSACTION);
 		return -1;
 	}
-	if (txn_begin(false) == NULL)
+	if (txn_begin() == NULL)
 		return -1;
 	return 0;
 }
diff --git a/src/box/txn.h b/src/box/txn.h
index fe8a299f2..7f999b8e9 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -154,11 +154,6 @@ struct txn {
 	 * already assigned LSN.
 	 */
 	int n_applier_rows;
-	/**
-	 * True if this transaction is running in autocommit mode
-	 * (statement end causes an automatic transaction commit).
-	 */
-	bool is_autocommit;
 	/**
 	 * True if the transaction was aborted so should be
 	 * rolled back at commit.
@@ -206,7 +201,7 @@ in_txn()
  * @pre no transaction is active
  */
 struct txn *
-txn_begin(bool is_autocommit);
+txn_begin();
 
 /**
  * Commit a transaction.
diff --git a/src/box/vinyl.c b/src/box/vinyl.c
index 41918beba..fe258e784 100644
--- a/src/box/vinyl.c
+++ b/src/box/vinyl.c
@@ -2399,10 +2399,8 @@ vinyl_engine_begin(struct engine *engine, struct txn *txn)
 	txn->engine_tx = vy_tx_begin(env->xm);
 	if (txn->engine_tx == NULL)
 		return -1;
-	if (!txn->is_autocommit) {
-		trigger_create(&txn->fiber_on_stop, txn_on_stop, NULL, NULL);
-		trigger_add(&fiber()->on_stop, &txn->fiber_on_stop);
-	}
+	trigger_create(&txn->fiber_on_stop, txn_on_stop, NULL, NULL);
+	trigger_add(&fiber()->on_stop, &txn->fiber_on_stop);
 	return 0;
 }
 
@@ -2472,8 +2470,7 @@ vinyl_engine_commit(struct engine *engine, struct txn *txn)
 	vy_regulator_check_dump_watermark(&env->regulator);
 
 	txn->engine_tx = NULL;
-	if (!txn->is_autocommit)
-		trigger_clear(&txn->fiber_on_stop);
+	trigger_clear(&txn->fiber_on_stop);
 }
 
 static void
@@ -2487,8 +2484,7 @@ vinyl_engine_rollback(struct engine *engine, struct txn *txn)
 	vy_tx_rollback(tx);
 
 	txn->engine_tx = NULL;
-	if (!txn->is_autocommit)
-		trigger_clear(&txn->fiber_on_stop);
+	trigger_clear(&txn->fiber_on_stop);
 }
 
 static int
-- 
2.21.0