MDEV-17421: mtr does not restart the server whose parameters were changed

If a mtr test runs multiple servers and only some of them get
restarted on whatever reason with new command-line parameters,
then subsequent mtr test may fail, because no cleanup is performed.
Replication and Galera test suites are affected.

In the mtr script, there is a server_need_restart function
that decides whether we need to start a new mysqld process before
the new (next) test. If the mysqld parameters were changed in the
previous test - not necessarily the parameters of the primary mysqld
server, maybe even the secondary server parameters - this function
decides to start a new mysqld process. But since it does not remove
the old (changed) parameters, the new process starts with the
parameters changed by the *previous* test.

To correct this error, we must delete the modified process
parameters after checking that they have been changed during
the previous test.

This patch also simplifies and makes more stable the
galera_drop_database test, during debugging of which this
problem was detected.

https://jira.mariadb.org/browse/MDEV-17421

mysql-test/mysql-test-run.pl

@@ -5282,6 +5282,7 @@ sub server_need_restart {
         exists $server->{'restart_opts'})
     {
       my $use_dynamic_option_switch= 0;
+      delete $server->{'restart_opts'};
       if (!$use_dynamic_option_switch)
       {
 	mtr_verbose_restart($server, "running with different options '" .

mysql-test/suite/galera/disabled.def

@@ -34,4 +34,3 @@ partition : MDEV-13881 galera.partition failed in buildbot with wrong result
 galera_as_slave_replication_budle : MDEV-15785 Test case galera_as_slave_replication_bundle caused debug assertion
 galera_wan : MDEV-17259: Test failure on galera.galera_wan
 galera_pc_ignore_sb : MDEV-17357 Test failure on galera.galera_pc_ignore_sb
-galera_drop_database : test

mysql-test/suite/galera/r/galera_mtr_restart_t1.result

+weight=111

mysql-test/suite/galera/r/galera_mtr_restart_t2.result

+weight=1

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

@@ -9,6 +9,7 @@
 --let $node_2=node_2
 --source include/auto_increment_offset_save.inc
 
+# Create test database with two sets of the FTS indexes:
 CREATE DATABASE fts;
 USE fts;
 CREATE TABLE fts_t1 (f1 INT PRIMARY KEY AUTO_INCREMENT, f2 VARCHAR(100), FULLTEXT (f2)) ENGINE=InnoDB;
@@ -23,34 +24,19 @@ DROP TABLE ten;
 UPDATE fts_t1 SET f2 = 'abcd';
 UPDATE fts_t2 SET f2 = 'efjh';
 
+# Restart the second node:
 --connection node_2
-let $wsrep_cluster_address = `SELECT @@global.wsrep_node_incoming_address`;
 --source include/restart_mysqld.inc
 
 --connection node_1
 --let $wait_condition = SELECT VARIABLE_VALUE = 2 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
 --source include/wait_condition.inc
 
---let $galera_connection_name = node_2a
---let $galera_server_number = 2
---source include/galera_connect.inc
---connection node_2a
+--connection node_2
 --source include/wait_until_ready.inc
 
+# Drop the tables and database after nodes restarted:
 --connection node_1
---let $restart_parameters = --wsrep-cluster-address=gcomm://$wsrep_cluster_address
---source include/restart_mysqld.inc
-
---connection node_2a
---let $wait_condition = SELECT VARIABLE_VALUE = 2 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
---source include/wait_condition.inc
-
---let $galera_connection_name = node_1a
---let $galera_server_number = 1
---source include/galera_connect.inc
---connection node_1a
---source include/wait_until_ready.inc
-
 USE fts;
 DROP TABLE fts_t1;
 DROP TABLE fts_t2;
@@ -58,8 +44,4 @@ SHOW TABLES;
 DROP DATABASE fts;
 
 # Restore original auto_increment_offset values.
---let $node_1=node_1a
---let $node_2=node_2a
 --source include/auto_increment_offset_restore.inc
-
---source include/galera_end.inc

mysql-test/suite/galera/t/galera_mtr_restart_t1.test

+# This test verifies that mtr will restart the mysqld process,
+# whose parameters were changed during the test. The verification
+# itself is carried out in the following galera_mtr_restart_t2
+# test. If mtr restart the mysqld process, then the pc.weight
+# value will be reset to the default ("1"), but if there is no
+# restart, then we will see the changed value ("111") during
+# the next test.
+#
+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+# Save original auto_increment_offset values.
+--let $node_1=node_1
+--let $node_2=node_2
+--source include/auto_increment_offset_save.inc
+
+--connection node_2
+--let $restart_parameters = --wsrep_provider_options=pc.weight=111;repl.causal_read_timeout=PT90S;evs.suspect_timeout=PT10S;evs.inactive_timeout=PT30S;evs.install_timeout=PT15S
+--source include/restart_mysqld.inc
+
+--connection node_1
+--let $wait_condition = SELECT VARIABLE_VALUE = 2 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
+--source include/wait_condition.inc
+
+--connection node_2
+--source include/wait_until_ready.inc
+
+# Check that the parameter value really changed:
+--let $gp = `SELECT SUBSTR(@@wsrep_provider_options, LOCATE('pc.weight =', @@wsrep_provider_options) + LENGTH('pc.weight = '))`
+--let $weight = `SELECT SUBSTR('$gp', 1, LOCATE(';', '$gp') - 1)`
+--echo weight=$weight
+
+# Restore original auto_increment_offset values.
+--connection node_1
+--source include/auto_increment_offset_restore.inc

mysql-test/suite/galera/t/galera_mtr_restart_t2.test

+# This test verifies that mtr will restart the mysqld process,
+# whose parameters were changed during the previous test. If mtr
+# restart the mysqld process, then the pc.weight value will be
+# reset to the default ("1"), but if there is no restart, then
+# we will see the changed value ("111") in this test.
+#
+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+--connection node_2
+--let $gp = `SELECT SUBSTR(@@wsrep_provider_options, LOCATE('pc.weight =', @@wsrep_provider_options) + LENGTH('pc.weight = '))`
+--let $weight = `SELECT SUBSTR('$gp', 1, LOCATE(';', '$gp') - 1)`
+--echo weight=$weight

mysql-test/suite/rpl/r/mtr_restart_t1.result

+include/master-slave.inc
+[connection master]
+include/rpl_stop_server.inc [server_number=1]
+new auto_increment_offset=111
+include/rpl_end.inc

mysql-test/suite/rpl/r/mtr_restart_t2.result

+include/master-slave.inc
+[connection master]
+auto_increment_offset=1
+include/rpl_end.inc

mysql-test/suite/rpl/t/mtr_restart_t1.test

+# This test verifies that mtr will restart the mysqld process,
+# whose parameters were changed during the test. The verification
+# itself is carried out in the following mtr_restart_t2 test.
+# If mtr restart the mysqld process, then the auto_increment_offset
+# parameter value will be reset to the default ("1"), but if there
+# is no restart, then we will see the changed value ("111") during
+# the next test.
+#
+--source include/have_binlog_format_row.inc
+--source include/master-slave.inc
+
+connection master;
+
+let $auto_increment_offset = `SELECT @@global.auto_increment_offset`;
+
+--let $rpl_server_number=1
+source include/rpl_stop_server.inc;
+--let $rpl_server_parameters=--auto-increment-offset=111
+--let $keep_include_silent=1
+source include/rpl_start_server.inc;
+--let $keep_include_silent=0
+
+let $auto_increment_offset_new = `SELECT @@global.auto_increment_offset`;
+--echo new auto_increment_offset=$auto_increment_offset_new
+
+--disable_query_log
+--eval SET @@global.auto_increment_offset = $auto_increment_offset;
+--enable_query_log
+
+--connection master
+--source include/rpl_end.inc

mysql-test/suite/rpl/t/mtr_restart_t2.test

+# This test verifies that mtr will restart the mysqld process,
+# whose parameters were changed during the previous test. If mtr
+# restart the mysqld process, then the auto_increment_offsert
+# parameter value will be reset to the default ("1"), but if there
+# is no restart, then we will see the changed value ("111") in
+# this test.
+#
+--source include/have_binlog_format_row.inc
+--source include/master-slave.inc
+
+connection master;
+
+let $auto_increment_offset = `SELECT @@global.auto_increment_offset`;
+
+--echo auto_increment_offset=$auto_increment_offset
+
+--connection master
+--source include/rpl_end.inc