MDEV-9290 : InnoDB: Assertion failure in file trx0sys.cc line 353

As a fix for MDEV-8208, for initial wsrep threads, the
invocation of init_for_queries() was moved after plugins
were initialized. Due to which, OPTION_BEGIN bit of wsrep
applier THD (originally set in wsrep_replication_process)
got reset due to implicit commit within init_for_queries().
As a result, events from a multi-statement transaction from
another node were committed separately by the applier thread,
which leads to an assertion as they all carry same seqno.

Fixed by making sure that variable.option_bits are restored
post init_for_queries(). Also restored server_status.
Added a test case.

mysql-test/suite/galera/r/mdev_9290.result

+#
+# MDEV-9290 : InnoDB: Assertion failure in file trx0sys.cc line 353
+# InnoDB: Failing assertion: xid_seqno > trx_sys_cur_xid_seqno
+#
+CREATE TABLE t1 (i INT) ENGINE=InnoDB;
+START TRANSACTION;
+INSERT INTO t1 VALUES (1);
+INSERT INTO t1 VALUES (2);
+COMMIT;
+SELECT * FROM t1;
+i
+1
+2
+DROP TABLE t1;

mysql-test/suite/galera/t/mdev_9290.test

+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+--echo #
+--echo # MDEV-9290 : InnoDB: Assertion failure in file trx0sys.cc line 353
+--echo # InnoDB: Failing assertion: xid_seqno > trx_sys_cur_xid_seqno
+--echo #
+
+--connection node_1
+CREATE TABLE t1 (i INT) ENGINE=InnoDB;
+
+--connection node_2
+# Note: a multi-statement transaction should always be the "first" one to execute
+# on this node.
+START TRANSACTION;
+INSERT INTO t1 VALUES (1);
+INSERT INTO t1 VALUES (2);
+COMMIT;
+
+--connection node_1
+SELECT * FROM t1;
+DROP TABLE t1;
+
+--source include/galera_end.inc

sql/mysqld.cc

@@ -4617,10 +4617,20 @@ a file name for --log-bin-index option", opt_binlog_index_name);
         THD *current_thd_saved= current_thd;
         my_pthread_setspecific_ptr(THR_THD, tmp);
 
+        /*
+          Also save/restore server_status and variables.option_bits and they
+          get altered during init_for_queries().
+        */
+        unsigned int server_status_saved= tmp->server_status;
+        ulonglong option_bits_saved= tmp->variables.option_bits;
+
         tmp->init_for_queries();
 
         /* Restore current_thd. */
         my_pthread_setspecific_ptr(THR_THD, current_thd_saved);
+
+        tmp->server_status= server_status_saved;
+        tmp->variables.option_bits= option_bits_saved;
       }
     }
     mysql_mutex_unlock(&LOCK_thread_count);
@@ -4984,7 +4994,7 @@ error:
   WSREP_ERROR("Failed to create/initialize system thread");
 
   /* Abort if its the first applier/rollbacker thread. */
-  if (wsrep_creating_startup_threads < 2)
+  if (wsrep_creating_startup_threads == 1)
     unireg_abort(1);
   else
     return NULL;