[tarantool-patches] [PATCH 3/3] Transaction support for applier

[Georgy Kirichenko <georgy@tarantool.org>]

Applier fetch incoming rows to form a transaction and then apply it.
In case of replication all local changes moved to an journal entry
tail to form a separate transaction (like autonomous transaction)
to be able to replicate changes back so applier assumes that transactions
could not be mixed in a replication stream.

Closes: #2798
Needed for: #980
---
 src/box/applier.cc                    | 243 ++++++++++++++++++++------
 src/box/txn.c                         |  21 ++-
 src/box/txn.h                         |   4 +
 test/replication/transaction.result   | 240 +++++++++++++++++++++++++
 test/replication/transaction.test.lua |  86 +++++++++
 5 files changed, 534 insertions(+), 60 deletions(-)
 create mode 100644 test/replication/transaction.result
 create mode 100644 test/replication/transaction.test.lua

diff --git a/src/box/applier.cc b/src/box/applier.cc
index 3222b041d..dfabbe5ab 100644
--- a/src/box/applier.cc
+++ b/src/box/applier.cc
@@ -48,6 +48,12 @@
 #include "session.h"
 #include "cfg.h"
 #include "box.h"
+#include "txn.h"
+
+enum {
+	/* Initial capacity of rows array. */
+	APPLIER_TX_INITIAL_ROW_COUNT = 16,
+};
 
 STRS(applier_state, applier_STATE);
 
@@ -380,6 +386,176 @@ applier_join(struct applier *applier)
 	applier_set_state(applier, APPLIER_READY);
 }
 
+/**
+ * Read one transaction from network using applier's input buffer.
+ * Transaction rows are placed onto fiber gc region.
+ * We could not use applier input buffer for that because rpos is adjusted
+ * after each xrow decoding and corresponding network input space is going
+ * to be reused.
+ *
+ * Return count of transaction rows and put row's header pointers into rows
+ * array.
+ */
+static int
+applier_read_tx(struct applier *applier, struct xrow_header **rows)
+{
+	struct ev_io *coio = &applier->io;
+	struct ibuf *ibuf = &applier->ibuf;
+	int64_t tsn = 0;
+	int row_capacity = APPLIER_TX_INITIAL_ROW_COUNT;
+	struct xrow_header *first_row, *row;
+	first_row = (struct xrow_header *)region_alloc(&fiber()->gc,
+						       row_capacity *
+						       sizeof(struct xrow_header));
+	if (first_row == NULL) {
+		diag_set(OutOfMemory, sizeof(struct xrow_header) * row_capacity,
+			 "region", "struct xrow_header");
+		goto error;
+	}
+	row = first_row;
+
+	do {
+		if (row == first_row + row_capacity) {
+			/* Realloc rows array. */
+			row = (struct xrow_header *)region_alloc(&fiber()->gc,
+								 row_capacity *
+								 sizeof(struct xrow_header) << 1);
+			if (row == NULL) {
+				diag_set(OutOfMemory,
+					 sizeof(struct xrow_header) *
+					 row_capacity << 1,
+					 "region", "struct xrow_header");
+				goto error;
+			}
+			memcpy(row, first_row, row_capacity *
+					       sizeof(struct xrow_header) << 1);
+			first_row = row;
+			row = first_row + row_capacity;
+			row_capacity <<= 1;
+		}
+
+		double timeout = replication_disconnect_timeout();
+		/*
+		 * Unfortunately we do not have C-version of coio read xrow
+		 * functions yet so use try-catch guard as workaround.
+		 */
+		try {
+			/*
+			 * Tarantool < 1.7.7 does not send periodic heartbeat
+			 * messages so we can't assume that if we haven't heard
+			 * from the master for quite a while the connection is
+			 * broken - the master might just be idle.
+			 */
+			if (applier->version_id < version_id(1, 7, 7))
+				coio_read_xrow(coio, ibuf, row);
+			else
+				coio_read_xrow_timeout_xc(coio, ibuf, row, timeout);
+		} catch (...) {
+			goto error;
+		}
+
+		if (iproto_type_is_error(row->type)) {
+			xrow_decode_error(row);
+			goto error;
+		}
+
+		/* Replication request. */
+		if (row->replica_id == REPLICA_ID_NIL ||
+		    row->replica_id >= VCLOCK_MAX) {
+			/*
+			 * A safety net, this can only occur
+			 * if we're fed a strangely broken xlog.
+			 */
+			diag_set(ClientError, ER_UNKNOWN_REPLICA,
+				 int2str(row->replica_id),
+				 tt_uuid_str(&REPLICASET_UUID));
+			goto error;
+		}
+		if (row == first_row) {
+			/*
+			 * First row in a transaction. In order to enforce
+			 * consistency check that first row lsn and replica id
+			 * match with transaction.
+			 */
+			tsn = row->tsn;
+			if (row->lsn != tsn) {
+				/* There is not a first row in the transactions. */
+				diag_set(ClientError, ER_PROTOCOL,
+					 "Not a first row in a transaction");
+				goto error;
+			}
+		}
+		if (tsn != row->tsn) {
+			/* We are not able to handle interleaving transactions. */
+			diag_set(ClientError, ER_UNSUPPORTED,
+				 "replications",
+				 "interleaving transactions");
+			goto error;
+		}
+
+
+		applier->lag = ev_now(loop()) - row->tm;
+		applier->last_row_time = ev_monotonic_now(loop());
+
+		if (row->body->iov_base != NULL) {
+			/* Save row bodies to gc region. */
+			void *new_base = region_alloc(&fiber()->gc,
+						      row->body->iov_len);
+			if (new_base == NULL) {
+				diag_set(OutOfMemory, row->body->iov_len,
+					 "slab", "xrow_data");
+				goto error;
+			}
+			memcpy(new_base, row->body->iov_base, row->body->iov_len);
+			/* Adjust row body pointers. */
+			row->body->iov_base = new_base;
+		}
+
+	} while (row->is_commit == 0 && ++row);
+
+	*rows = first_row;
+	return row - first_row + 1;
+error:
+	return -1;
+}
+
+static int
+applier_apply_tx(struct xrow_header *first_row, struct xrow_header *last_row)
+{
+	int res = 0;
+	struct txn *txn = NULL;
+	struct xrow_header *row = first_row;
+	if (first_row != last_row)
+		txn = txn_begin(false);
+	while (row <= last_row && res == 0) {
+		res = apply_row(row);
+		struct error *e;
+		if (res != 0 &&
+		    (e = diag_last_error(diag_get()))->type ==
+			    &type_ClientError &&
+		    box_error_code(e) == ER_TUPLE_FOUND &&
+		    replication_skip_conflict) {
+			/*
+			 * In case of ER_TUPLE_FOUND error and enabled
+			 * replication_skip_conflict configuration
+			 * option, skip applying the foreign row and
+			 * replace it with NOP in the local write ahead
+			 * log.
+			 */
+			diag_clear(diag_get());
+			(row)->type = IPROTO_NOP;
+			(row)->bodycnt = 0;
+			res = apply_row(row);
+		}
+		++row;
+	}
+	if (res == 0 && txn != NULL)
+		res = txn_commit(txn);
+	if (res != 0)
+		txn_rollback();
+	return res;
+}
+
 /**
  * Execute and process SUBSCRIBE request (follow updates from a master).
  */
@@ -509,36 +685,14 @@ applier_subscribe(struct applier *applier)
 			applier_set_state(applier, APPLIER_FOLLOW);
 		}
 
-		/*
-		 * Tarantool < 1.7.7 does not send periodic heartbeat
-		 * messages so we can't assume that if we haven't heard
-		 * from the master for quite a while the connection is
-		 * broken - the master might just be idle.
-		 */
-		if (applier->version_id < version_id(1, 7, 7)) {
-			coio_read_xrow(coio, ibuf, &row);
-		} else {
-			double timeout = replication_disconnect_timeout();
-			coio_read_xrow_timeout_xc(coio, ibuf, &row, timeout);
-		}
+		struct xrow_header *tx_rows;
+		int row_count = applier_read_tx(applier, &tx_rows);
+		if (row_count < 0)
+			diag_raise();
 
-		if (iproto_type_is_error(row.type))
-			xrow_decode_error_xc(&row);  /* error */
-		/* Replication request. */
-		if (row.replica_id == REPLICA_ID_NIL ||
-		    row.replica_id >= VCLOCK_MAX) {
-			/*
-			 * A safety net, this can only occur
-			 * if we're fed a strangely broken xlog.
-			 */
-			tnt_raise(ClientError, ER_UNKNOWN_REPLICA,
-				  int2str(row.replica_id),
-				  tt_uuid_str(&REPLICASET_UUID));
-		}
-
-		applier->lag = ev_now(loop()) - row.tm;
+		applier->lag = ev_now(loop()) - (tx_rows + row_count - 1)->tm;
 		applier->last_row_time = ev_monotonic_now(loop());
-		struct replica *replica = replica_by_id(row.replica_id);
+		struct replica *replica = replica_by_id(tx_rows->replica_id);
 		struct latch *latch = (replica ? &replica->order_latch :
 				       &replicaset.applier.order_latch);
 		/*
@@ -548,33 +702,12 @@ applier_subscribe(struct applier *applier)
 		 * that belong to the same server id.
 		 */
 		latch_lock(latch);
-		if (vclock_get(&replicaset.vclock, row.replica_id) < row.lsn) {
-			int res = apply_row(&row);
-			if (res != 0) {
-				struct error *e = diag_last_error(diag_get());
-				/*
-				 * In case of ER_TUPLE_FOUND error and enabled
-				 * replication_skip_conflict configuration
-				 * option, skip applying the foreign row and
-				 * replace it with NOP in the local write ahead
-				 * log.
-				 */
-				if (e->type == &type_ClientError &&
-				    box_error_code(e) == ER_TUPLE_FOUND &&
-				    replication_skip_conflict) {
-					diag_clear(diag_get());
-					struct xrow_header nop;
-					nop.type = IPROTO_NOP;
-					nop.bodycnt = 0;
-					nop.replica_id = row.replica_id;
-					nop.lsn = row.lsn;
-					res = apply_row(&nop);
-				}
-			}
-			if (res != 0) {
-				latch_unlock(latch);
-				diag_raise();
-			}
+		if (vclock_get(&replicaset.vclock,
+			       tx_rows->replica_id) < tx_rows->lsn &&
+		    applier_apply_tx(tx_rows, tx_rows + row_count - 1) != 0) {
+			latch_unlock(latch);
+			fiber_gc();
+			diag_raise();
 		}
 		latch_unlock(latch);
 
diff --git a/src/box/txn.c b/src/box/txn.c
index 7900fb3ab..f6bf72d0c 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -34,6 +34,7 @@
 #include "journal.h"
 #include <fiber.h>
 #include "xrow.h"
+#include "replication.h"
 
 double too_long_threshold;
 
@@ -141,6 +142,7 @@ txn_begin(bool is_autocommit)
 	/* Initialize members explicitly to save time on memset() */
 	stailq_create(&txn->stmts);
 	txn->n_rows = 0;
+	txn->n_remote_rows = 0;
 	txn->is_autocommit = is_autocommit;
 	txn->has_triggers  = false;
 	txn->is_aborted = false;
@@ -233,6 +235,9 @@ txn_commit_stmt(struct txn *txn, struct request *request)
 	if (stmt->space == NULL || !space_is_temporary(stmt->space)) {
 		if (txn_add_redo(stmt, request) != 0)
 			goto fail;
+		if (stmt->row->replica_id != 0 &&
+		    stmt->row->replica_id != instance_id)
+			++txn->n_remote_rows;
 		++txn->n_rows;
 	}
 	/*
@@ -271,14 +276,20 @@ txn_write_to_wal(struct txn *txn)
 		return -1;
 
 	struct txn_stmt *stmt;
-	struct xrow_header **row = req->rows;
+	struct xrow_header **remote_row = req->rows;
+	struct xrow_header **local_row = req->rows + txn->n_remote_rows;
 	stailq_foreach_entry(stmt, &txn->stmts, next) {
 		if (stmt->row == NULL)
 			continue; /* A read (e.g. select) request */
-		*row++ = stmt->row;
+		if (stmt->row->replica_id != 0 &&
+		    stmt->row->replica_id != instance_id)
+			*remote_row++ = stmt->row;
+		else
+			*local_row++ = stmt->row;
 		req->approx_len += xrow_approx_len(stmt->row);
 	}
-	assert(row == req->rows + req->n_rows);
+	assert(remote_row == req->rows + txn->n_remote_rows);
+	assert(local_row == req->rows + req->n_rows);
 
 	ev_tstamp start = ev_monotonic_now(loop());
 	int64_t res = journal_write(req);
@@ -399,8 +410,6 @@ txn_rollback()
 		txn_stmt_unref_tuples(stmt);
 
 	TRASH(txn);
-	/** Free volatile txn memory. */
-	fiber_gc();
 	fiber_set_txn(fiber(), NULL);
 }
 
@@ -480,6 +489,8 @@ box_txn_rollback()
 		return -1;
 	}
 	txn_rollback(); /* doesn't throw */
+	/** Free volatile txn memory. */
+	fiber_gc();
 	return 0;
 }
 
diff --git a/src/box/txn.h b/src/box/txn.h
index de5cb0de4..2791fdf73 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -142,6 +142,10 @@ struct txn {
 	struct stailq stmts;
 	/** Total number of WAL rows in this txn. */
 	int n_rows;
+	/**
+	 * Count of rows generated on a remote replica.
+	 */
+	int n_remote_rows;
 	/**
 	 * True if this transaction is running in autocommit mode
 	 * (statement end causes an automatic transaction commit).
diff --git a/test/replication/transaction.result b/test/replication/transaction.result
new file mode 100644
index 000000000..009f84430
--- /dev/null
+++ b/test/replication/transaction.result
@@ -0,0 +1,240 @@
+env = require('test_run')
+---
+...
+test_run = env.new()
+---
+...
+box.schema.user.grant('guest', 'replication')
+---
+...
+s = box.schema.space.create('test', {engine = test_run:get_cfg('engine')})
+---
+...
+_ = s:create_index('pk')
+---
+...
+-- transaction w/o conflict
+box.begin() s:insert({1, 'm'}) s:insert({2, 'm'}) box.commit()
+---
+...
+test_run:cmd("create server replica with rpl_master=default, script='replication/replica.lua'")
+---
+- true
+...
+test_run:cmd("start server replica")
+---
+- true
+...
+test_run:cmd("switch replica")
+---
+- true
+...
+-- insert a conflicting row
+box.space.test:replace({4, 'r'})
+---
+- [4, 'r']
+...
+v1 = box.info.vclock
+---
+...
+test_run:cmd("switch default")
+---
+- true
+...
+-- create a two-row transaction with conflicting second
+box.begin() s:insert({3, 'm'}) s:insert({4, 'm'}) box.commit()
+---
+...
+-- create a third transaction
+box.begin() s:insert({5, 'm'}) s:insert({6, 'm'}) s:insert({7, 'm'}) box.commit()
+---
+...
+test_run:cmd("switch replica")
+---
+- true
+...
+-- nothing was applied
+v1[1] == box.info.vclock[1]
+---
+- true
+...
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [4, 'r']
+...
+-- check replication status
+box.info.replication[1].upstream.status
+---
+- stopped
+...
+box.info.replication[1].upstream.message
+---
+- Duplicate key exists in unique index 'pk' in space 'test'
+...
+-- set conflict to third transaction
+box.space.test:delete({3})
+---
+...
+box.space.test:replace({6, 'r'})
+---
+- [6, 'r']
+...
+-- restart replication
+replication = box.cfg.replication
+---
+...
+box.cfg{replication = {}}
+---
+...
+box.cfg{replication = replication}
+---
+...
+-- replication stopped of third transaction
+v1[1] + 2 == box.info.vclock[1]
+---
+- false
+...
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [4, 'r']
+  - [6, 'r']
+...
+-- check replication status
+box.info.replication[1].upstream.status
+---
+- stopped
+...
+box.info.replication[1].upstream.message
+---
+- Duplicate key exists in unique index 'pk' in space 'test'
+...
+-- check restart does not help
+test_run:cmd("switch default")
+---
+- true
+...
+test_run:cmd("restart server replica")
+---
+- true
+...
+test_run:cmd("switch replica")
+---
+- true
+...
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [4, 'r']
+  - [6, 'r']
+...
+-- set skip conflict rows and check that non-conflicting were applied
+replication = box.cfg.replication
+---
+...
+box.cfg{replication = {}, replication_skip_conflict = true}
+---
+...
+box.cfg{replication = replication}
+---
+...
+-- check last transaction applied without conflicting row
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [3, 'm']
+  - [4, 'r']
+  - [5, 'm']
+  - [6, 'r']
+  - [7, 'm']
+...
+box.info.replication[1].upstream.status
+---
+- follow
+...
+-- make some new conflicting rows with skip-conflicts
+box.space.test:replace({8, 'r'})
+---
+- [8, 'r']
+...
+box.space.test:replace({9, 'r'})
+---
+- [9, 'r']
+...
+-- issue a conflicting tx
+test_run:cmd("switch default")
+---
+- true
+...
+box.begin() s:insert({8, 'm'}) s:insert({9, 'm'}) box.commit()
+---
+...
+test_run:cmd("switch replica")
+---
+- true
+...
+-- vclock should be increased but rows skipped
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [3, 'm']
+  - [4, 'r']
+  - [5, 'm']
+  - [6, 'r']
+  - [7, 'm']
+  - [8, 'r']
+  - [9, 'r']
+...
+-- check restart does not change something
+test_run:cmd("switch default")
+---
+- true
+...
+test_run:cmd("restart server replica")
+---
+- true
+...
+test_run:cmd("switch replica")
+---
+- true
+...
+box.space.test:select()
+---
+- - [1, 'm']
+  - [2, 'm']
+  - [3, 'm']
+  - [4, 'r']
+  - [5, 'm']
+  - [6, 'r']
+  - [7, 'm']
+  - [8, 'r']
+  - [9, 'r']
+...
+box.info.replication[1].upstream.status
+---
+- follow
+...
+test_run:cmd("switch default")
+---
+- true
+...
+test_run:cmd("stop server replica")
+---
+- true
+...
+test_run:cmd("cleanup server replica")
+---
+- true
+...
+box.schema.user.revoke('guest', 'replication')
+---
+...
+s:drop()
+---
+...
diff --git a/test/replication/transaction.test.lua b/test/replication/transaction.test.lua
new file mode 100644
index 000000000..47003c644
--- /dev/null
+++ b/test/replication/transaction.test.lua
@@ -0,0 +1,86 @@
+env = require('test_run')
+test_run = env.new()
+box.schema.user.grant('guest', 'replication')
+
+s = box.schema.space.create('test', {engine = test_run:get_cfg('engine')})
+_ = s:create_index('pk')
+
+-- transaction w/o conflict
+box.begin() s:insert({1, 'm'}) s:insert({2, 'm'}) box.commit()
+
+test_run:cmd("create server replica with rpl_master=default, script='replication/replica.lua'")
+test_run:cmd("start server replica")
+test_run:cmd("switch replica")
+
+-- insert a conflicting row
+box.space.test:replace({4, 'r'})
+v1 = box.info.vclock
+
+test_run:cmd("switch default")
+-- create a two-row transaction with conflicting second
+box.begin() s:insert({3, 'm'}) s:insert({4, 'm'}) box.commit()
+-- create a third transaction
+box.begin() s:insert({5, 'm'}) s:insert({6, 'm'}) s:insert({7, 'm'}) box.commit()
+
+test_run:cmd("switch replica")
+-- nothing was applied
+v1[1] == box.info.vclock[1]
+box.space.test:select()
+-- check replication status
+box.info.replication[1].upstream.status
+box.info.replication[1].upstream.message
+-- set conflict to third transaction
+box.space.test:delete({3})
+box.space.test:replace({6, 'r'})
+-- restart replication
+replication = box.cfg.replication
+box.cfg{replication = {}}
+box.cfg{replication = replication}
+-- replication stopped of third transaction
+v1[1] + 2 == box.info.vclock[1]
+box.space.test:select()
+-- check replication status
+box.info.replication[1].upstream.status
+box.info.replication[1].upstream.message
+
+-- check restart does not help
+test_run:cmd("switch default")
+test_run:cmd("restart server replica")
+test_run:cmd("switch replica")
+
+box.space.test:select()
+-- set skip conflict rows and check that non-conflicting were applied
+replication = box.cfg.replication
+box.cfg{replication = {}, replication_skip_conflict = true}
+box.cfg{replication = replication}
+
+-- check last transaction applied without conflicting row
+box.space.test:select()
+box.info.replication[1].upstream.status
+
+-- make some new conflicting rows with skip-conflicts
+box.space.test:replace({8, 'r'})
+box.space.test:replace({9, 'r'})
+
+-- issue a conflicting tx
+test_run:cmd("switch default")
+box.begin() s:insert({8, 'm'}) s:insert({9, 'm'}) box.commit()
+
+test_run:cmd("switch replica")
+-- vclock should be increased but rows skipped
+box.space.test:select()
+
+-- check restart does not change something
+test_run:cmd("switch default")
+test_run:cmd("restart server replica")
+test_run:cmd("switch replica")
+
+box.space.test:select()
+box.info.replication[1].upstream.status
+
+test_run:cmd("switch default")
+test_run:cmd("stop server replica")
+test_run:cmd("cleanup server replica")
+
+box.schema.user.revoke('guest', 'replication')
+s:drop()
-- 
2.21.0