MDEV-20793 Assertion failed after replay.

Assertion failed in wsrep-lib after transaction replay which
failed due to conflict in certification.

- Implemented reproducible test case MDEV-20793 to reproduce the crash.
- Fixed wsrep-lib to deal with certification error during replay.

mysql-test/suite/galera/r/MDEV-20793.result

+connection node_2;
+connection node_1;
+CREATE TABLE t1 (f1 INT PRIMARY KEY, f2 INT);
+INSERT INTO t1 VALUES (1, 0), (5, 0);
+connection node_1_ctrl;
+SET SESSION wsrep_sync_wait = 0;
+SET GLOBAL wsrep_slave_threads = 2;
+connection node_1;
+SET SESSION wsrep_retry_autocommit = 0;
+START TRANSACTION;
+UPDATE t1 SET f2 = 1;
+SET SESSION debug_sync = "wsrep_before_replay SIGNAL reached WAIT_FOR continue";
+connection node_1_ctrl;
+SET GLOBAL wsrep_provider_options = 'dbug=d,apply_monitor_slave_enter_sync';
+connection node_2;
+INSERT INTO t1 VALUES (2, 2);
+connection node_1_ctrl;
+SET SESSION wsrep_on = 0;
+SET SESSION wsrep_on = 1;
+SET GLOBAL wsrep_provider_options = 'dbug=';
+SET GLOBAL wsrep_provider_options = 'dbug=d,local_monitor_slave_enter_sync';
+connection node_2;
+UPDATE t1 SET f2 = 2 WHERE f1 = 5;
+connection node_1_ctrl;
+SET SESSION wsrep_on = 0;
+SET SESSION wsrep_on = 1;
+connection node_1;
+COMMIT;
+connection node_1_ctrl;
+SET GLOBAL wsrep_provider_options = 'signal=apply_monitor_slave_enter_sync';
+SET SESSION debug_sync = "now WAIT_FOR reached";
+SET GLOBAL wsrep_provider_options = 'signal=local_monitor_slave_enter_sync';
+SET GLOBAL wsrep_provider_options = 'dbug=';
+SET SESSION debug_sync = "now SIGNAL continue";
+connection node_1;
+ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
+SET debug_sync = "RESET";
+DROP TABLE t1;
+SET GLOBAL wsrep_slave_threads = 1;

mysql-test/suite/galera/t/MDEV-20793.test

+#
+# MDEV-20793 Assertion after certification failure during replay.
+#
+# The test outline:
+# In order to produce certification failure three transactions
+# are needed. One transaction is executing on node_1 and two others
+# on node_2. The first transaction from node_2 BF aborts the transaction
+# on node_1, but does not cause certification conflict. The second
+# transaction from node_2 will cause conflict and the transaction on
+# node_1 fails in certification during replay.
+#
+
+--source include/galera_cluster.inc
+
+CREATE TABLE t1 (f1 INT PRIMARY KEY, f2 INT);
+INSERT INTO t1 VALUES (1, 0), (5, 0);
+
+--let galera_connection_name = node_1_ctrl
+--let galera_server_number = 1
+--source include/galera_connect.inc
+--connection node_1_ctrl
+SET SESSION wsrep_sync_wait = 0;
+SET GLOBAL wsrep_slave_threads = 2;
+
+--connection node_1
+# Start transaction which takes gap lock 1 - 5
+SET SESSION wsrep_retry_autocommit = 0;
+START TRANSACTION;
+UPDATE t1 SET f2 = 1;
+SET SESSION debug_sync = "wsrep_before_replay SIGNAL reached WAIT_FOR continue";
+
+--connection node_1_ctrl
+--let $galera_sync_point = apply_monitor_slave_enter_sync
+--source include/galera_set_sync_point.inc
+
+--connection node_2
+# Insert into gap from other node. This generates BF abort but does not
+# conflict with update.
+INSERT INTO t1 VALUES (2, 2);
+
+--connection node_1_ctrl
+--source include/galera_wait_sync_point.inc
+--source include/galera_clear_sync_point.inc
+--let $galera_sync_point = local_monitor_slave_enter_sync
+--source include/galera_set_sync_point.inc
+
+# Make an update which will conflict with update on node_1
+--connection node_2
+UPDATE t1 SET f2 = 2 WHERE f1 = 5;
+
+--connection node_1_ctrl
+--let $galera_sync_point = apply_monitor_slave_enter_sync local_monitor_slave_enter_sync
+--source include/galera_wait_sync_point.inc
+
+--connection node_1
+--send COMMIT
+
+--connection node_1_ctrl
+--let $galera_sync_point = apply_monitor_slave_enter_sync
+--source include/galera_signal_sync_point.inc
+SET SESSION debug_sync = "now WAIT_FOR reached";
+
+--let $galera_sync_point = local_monitor_slave_enter_sync
+--source include/galera_signal_sync_point.inc
+--source include/galera_clear_sync_point.inc
+SET SESSION debug_sync = "now SIGNAL continue";
+
+--connection node_1
+--error ER_LOCK_DEADLOCK
+--reap
+
+SET debug_sync = "RESET";
+
+DROP TABLE t1;
+SET GLOBAL wsrep_slave_threads = 1;

sql/wsrep_high_priority_service.cc

@@ -598,9 +598,7 @@ Wsrep_replayer_service::~Wsrep_replayer_service()
   THD* replayer_thd= m_thd;
   THD* orig_thd= m_orig_thd;
 
-  /* Store replay result/state to original thread wsrep client
-     state and switch execution context back to original. */
-  orig_thd->wsrep_cs().after_replay(replayer_thd->wsrep_trx());
+  /* Switch execution context back to original. */
   wsrep_after_apply(replayer_thd);
   wsrep_after_command_ignore_result(replayer_thd);
   wsrep_close(replayer_thd);

wsrep-lib @ 76f7249b

-Subproject commit 90157ed1b0f8b3f0d1eb3d60ac93ce6d8da7ad77
+Subproject commit 76f7249b8df209a2a3cefd7d4bbf31f6c72812f1