MDEV-9247: Make default_master_connection settable globally

mysql-test/main/mysqld--help.result

@@ -264,6 +264,9 @@ The following specify which files/extra groups are read (specified before remain
  --deadlock-timeout-short=# 
  Short timeout for the two-step deadlock detection (in
  microseconds)
+ --default-master-connection=name 
+ Master connection to use for all slave variables and
+ slave commands
  --default-password-lifetime=# 
  This defines the global password expiration policy. 0
  means automatic password expiration is disabled. If the
@@ -1751,6 +1754,7 @@ deadlock-search-depth-long 15
 deadlock-search-depth-short 4
 deadlock-timeout-long 50000000
 deadlock-timeout-short 10000
+default-master-connection 
 default-password-lifetime 0
 default-regex-flags 
 default-storage-engine myisam

mysql-test/suite/multi_source/syntax.result

@@ -43,9 +43,13 @@ select @@default_master_connection;
 @@default_master_connection
 
 select @@global.default_master_connection;
-ERROR HY000: Variable 'default_master_connection' is a SESSION variable
+@@global.default_master_connection
+
 set @@global.default_master_connection='qqq';
-ERROR HY000: Variable 'default_master_connection' is a SESSION variable and can't be used with SET GLOBAL
+select @@global.default_master_connection;
+@@global.default_master_connection
+qqq
+set @@global.default_master_connection='';
 set @@default_master_connection='aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbcccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc';
 ERROR 42000: Variable 'default_master_connection' can't be set to the value of 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbcccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc'
 select @@default_master_connection;

mysql-test/suite/multi_source/syntax.test

@@ -45,10 +45,10 @@ sync_with_master 0, '';
 --echo #
 select @@default_master_connection;
 
---error 1238
 select @@global.default_master_connection;
---error 1228
 set @@global.default_master_connection='qqq';
+select @@global.default_master_connection;
+set @@global.default_master_connection='';
 --error 1231
 set @@default_master_connection='aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbcccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc';
 select @@default_master_connection;

mysql-test/suite/sys_vars/r/default_master_connection_basic.result

@@ -12,9 +12,13 @@ SELECT @@session.default_master_connection = '';
 @@session.default_master_connection = ''
 1
 SET @@global.default_master_connection = 'master1';
-ERROR HY000: Variable 'default_master_connection' is a SESSION variable and can't be used with SET GLOBAL
 SELECT @@global.default_master_connection;
-ERROR HY000: Variable 'default_master_connection' is a SESSION variable
+@@global.default_master_connection
+master1
+SET @@global.default_master_connection = '';
+SELECT @@global.default_master_connection;
+@@global.default_master_connection
+
 SET @@session.default_master_connection = 'master1';
 SELECT @@session.default_master_connection;
 @@session.default_master_connection
@@ -61,7 +65,8 @@ master2
 SELECT @@global.default_master_connection = VARIABLE_VALUE 
 FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES 
 WHERE VARIABLE_NAME='default_master_connection';
-ERROR HY000: Variable 'default_master_connection' is a SESSION variable
+@@global.default_master_connection = VARIABLE_VALUE
+1
 SELECT @@session.default_master_connection = VARIABLE_VALUE 
 FROM INFORMATION_SCHEMA.SESSION_VARIABLES
 WHERE VARIABLE_NAME='default_master_connection';
@@ -88,3 +93,27 @@ SET @@session.default_master_connection = @start_session_value;
 SELECT @@session.default_master_connection;
 @@session.default_master_connection
 
+SET @@global.default_master_connection = 'global';
+connect  con1,localhost,root,,;
+connection con1;
+SELECT @@session.default_master_connection;
+@@session.default_master_connection
+global
+connection default;
+disconnect con1;
+SET @@global.default_master_connection = '';
+# restart: --default-master-connection=master1
+SELECT @@global.default_master_connection;
+@@global.default_master_connection
+master1
+SELECT @@session.default_master_connection;
+@@session.default_master_connection
+master1
+connect  con2,localhost,root,,;
+connection con2;
+SELECT @@session.default_master_connection;
+@@session.default_master_connection
+master1
+connection default;
+disconnect con2;
+# restart

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -903,15 +903,15 @@ ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	DEFAULT_MASTER_CONNECTION
-VARIABLE_SCOPE	SESSION ONLY
+VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	VARCHAR
 VARIABLE_COMMENT	Master connection to use for all slave variables and slave commands
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
-COMMAND_LINE_ARGUMENT	NULL
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	DEFAULT_PASSWORD_LIFETIME
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	INT UNSIGNED

mysql-test/suite/sys_vars/t/default_master_connection_basic.test

@@ -1,7 +1,7 @@
 ############## mysql-test\t\default_master_connection_basic.test ###############
 # 
 # Implemented in the scope of MDEV-253
-# The variable is SESSION-only
+# Updated to SESSION-VAR (Global) scope in MDEV-9247
 #
 
 --source include/not_embedded.inc
@@ -29,12 +29,12 @@ SET @@session.default_master_connection = @start_session_value;
 SELECT @@session.default_master_connection = '';
 
 #################################################
-# Check that the GLOBAL scope is not applicable #
+# Check that the GLOBAL scope is applicable    #
 #################################################
 
---error ER_LOCAL_VARIABLE
 SET @@global.default_master_connection = 'master1';
---error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@global.default_master_connection;
+SET @@global.default_master_connection = '';
 SELECT @@global.default_master_connection;
 
 ####################################################################################
@@ -77,7 +77,6 @@ SELECT @@session.default_master_connection;
 #   Check if the value in GLOBAL & SESSION Tables matches value in variable   #
 ###############################################################################
 
---error ER_INCORRECT_GLOBAL_LOCAL_VAR
 SELECT @@global.default_master_connection = VARIABLE_VALUE 
 FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES 
 WHERE VARIABLE_NAME='default_master_connection';
@@ -117,6 +116,37 @@ SELECT default_master_connection = @@session.default_master_connection;
 SET @@session.default_master_connection = @start_session_value;
 SELECT @@session.default_master_connection;
 
+#####################################################################
+#  Check if global value is inherited by new connections (MDEV-9247)#
+#####################################################################
+
+SET @@global.default_master_connection = 'global';
+--connect (con1,localhost,root,,)
+--connection con1
+SELECT @@session.default_master_connection;
+--connection default
+--disconnect con1
+SET @@global.default_master_connection = '';
+
+#####################################################################
+#  Check if global value can be set via command line (MDEV-9247)    #
+#####################################################################
+
+--let $restart_parameters=--default-master-connection=master1
+--source include/restart_mysqld.inc
+
+SELECT @@global.default_master_connection;
+SELECT @@session.default_master_connection;
+
+--connect (con2,localhost,root,,)
+--connection con2
+SELECT @@session.default_master_connection;
+--connection default
+--disconnect con2
+
+# Clean up for subsequent tests if any (though this is the end)
+--let $restart_parameters=
+--source include/restart_mysqld.inc
 
 #############################################################
 #                 END OF default_master_connection TESTS    #

sql/mysqld.cc

@@ -9012,6 +9012,9 @@ static int get_options(int *argc_ptr, char ***argv_ptr)
 
   opt_init_connect.length=strlen(opt_init_connect.str);
   opt_init_slave.length=strlen(opt_init_slave.str);
+  global_system_variables.default_master_connection.length=
+    global_system_variables.default_master_connection.str ?
+    strlen(global_system_variables.default_master_connection.str) : 0;
 
   if (global_system_variables.low_priority_updates)
     thr_upgraded_concurrent_insert_lock= TL_WRITE_LOW_PRIORITY;

sql/sys_vars.cc

@@ -1481,7 +1481,7 @@ static bool check_master_connection(sys_var *self, THD *thd, set_var *var)
 static Sys_var_lexstring Sys_default_master_connection(
        "default_master_connection",
        "Master connection to use for all slave variables and slave commands",
-       SESSION_ONLY(default_master_connection), NO_CMD_LINE, DEFAULT(""),
+       SESSION_VAR(default_master_connection), CMD_LINE(REQUIRED_ARG), DEFAULT(""),
        NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_master_connection));
 #endif