MDEV-38202: add init_rpl_role in SHOW VARIABLES by introducing a read-only sys_var set at server startup

Author: Mahmoud-kh1

mysql-test/main/information_schema.result

@@ -1939,6 +1939,7 @@ drop table if exists t1;drop table if exists t1;
 drop table if exists t1;drop table if exists t1;
 drop table if exists t1;drop table if exists t1;
 INIT_FILE	
+INIT_RPL_ROLE	MASTER
 INIT_SLAVE	
 set global init_connect="";
 create table t0 select * from information_schema.global_status where VARIABLE_NAME='COM_SELECT';

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

@@ -0,0 +1,18 @@
+#  
+# MDEV-38202: add init_rpl_role in output of "show variables"   
+#  
+# it should show SLAVE as it is set in opt file
+SELECT @@global.init_rpl_role;
+@@global.init_rpl_role
+SLAVE
+SHOW GLOBAL VARIABLES LIKE 'init_rpl_role';
+Variable_name	Value
+init_rpl_role	SLAVE
+# as we want to see the intial value only it should be read-only 
+SET GLOBAL init_rpl_role = 'MASTER';
+ERROR HY000: Variable 'init_rpl_role' is a read only variable
+# it should show in INFORMATION_SCHEMA.GLOBAL_VARIABLES  
+SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES  
+WHERE VARIABLE_NAME = 'init_rpl_role';
+VARIABLE_NAME	VARIABLE_VALUE
+INIT_RPL_ROLE	SLAVE

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

@@ -1582,6 +1582,16 @@ NUMERIC_BLOCK_SIZE	NULL
 ENUM_VALUE_LIST	NULL
 READ_ONLY	YES
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	INIT_RPL_ROLE
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	ENUM
+VARIABLE_COMMENT	The replication role that the server was started with. Possible values are MASTER and SLAVE
+NUMERIC_MIN_VALUE	NULL
+NUMERIC_MAX_VALUE	NULL
+NUMERIC_BLOCK_SIZE	NULL
+ENUM_VALUE_LIST	MASTER,SLAVE
+READ_ONLY	YES
+COMMAND_LINE_ARGUMENT	NULL
 VARIABLE_NAME	INIT_SLAVE
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	VARCHAR

mysql-test/suite/sys_vars/t/init_rpl_role_variable_basic.opt

@@ -0,0 +1 @@
+--init-rpl-role=SLAVE

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

@@ -0,0 +1,17 @@
+--echo #  
+--echo # MDEV-38202: add init_rpl_role in output of "show variables"   
+--echo #  
+
+--echo # it should show SLAVE as it is set in opt file
+SELECT @@global.init_rpl_role; 
+
+SHOW GLOBAL VARIABLES LIKE 'init_rpl_role'; 
+
+--echo # as we want to see the intial value only it should be read-only 
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR  
+SET GLOBAL init_rpl_role = 'MASTER';
+
+
+--echo # it should show in INFORMATION_SCHEMA.GLOBAL_VARIABLES  
+SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES  
+  WHERE VARIABLE_NAME = 'init_rpl_role'; 

sql/mysqld.cc

@@ -9141,6 +9141,7 @@ static int get_options(int *argc_ptr, char ***argv_ptr)
     flush_time= 0;
 
 #ifdef HAVE_REPLICATION
+  init_rpl_role_val = rpl_status;
   if (init_slave_skip_errors(opt_slave_skip_errors))
     return 1;
   if (init_slave_transaction_retry_errors(opt_slave_transaction_retry_errors))

sql/repl_failsafe.cc

@@ -52,6 +52,7 @@ struct Slave_info
 
 Atomic_counter<uint32_t> binlog_dump_thread_count;
 ulong rpl_status=RPL_NULL;
+ulong init_rpl_role_val= RPL_AUTH_MASTER;
 mysql_mutex_t LOCK_rpl_status;
 
 const char *rpl_role_type[] = {"MASTER","SLAVE",NullS};

sql/repl_failsafe.h

@@ -29,6 +29,7 @@ typedef enum {RPL_AUTH_MASTER=0,RPL_IDLE_SLAVE,RPL_ACTIVE_SLAVE,
 	      RPL_ANY /* wild card used by change_rpl_status */ } RPL_STATUS;
 extern ulong rpl_status;
 
+extern ulong init_rpl_role_val;
 extern mysql_mutex_t LOCK_rpl_status;
 extern mysql_cond_t COND_rpl_status;
 extern TYPELIB rpl_role_typelib;

sql/sys_vars.cc

@@ -67,6 +67,7 @@
 #include "semisync_master.h"
 #include "semisync_slave.h"
 #include <ssl_compat.h>
+#include "repl_failsafe.h"
 #ifdef WITH_WSREP
 #include "wsrep_mysqld.h"
 #endif
@@ -1505,6 +1506,14 @@ Sys_init_slave(
        DEFAULT(""), &PLock_sys_init_slave,
        NOT_IN_BINLOG, ON_CHECK(check_init_string));
 
+#ifdef HAVE_REPLICATION 
+static Sys_var_enum Sys_init_rpl_role(  
+       "init_rpl_role",  
+       "The replication role that the server was started with. "  
+        "Possible values are MASTER and SLAVE", 
+       READ_ONLY GLOBAL_VAR(init_rpl_role_val), NO_CMD_LINE,  
+       rpl_role_type, DEFAULT(RPL_AUTH_MASTER));  
+#endif
 static Sys_var_ulong Sys_interactive_timeout(
        "interactive_timeout",
        "The number of seconds the server waits for activity on an interactive "