BUG#20471216: 5.6 WITH GTID_MODE=X CANT CONNECT TO 5.7.6 WITH GTID_MODE=X_PERMISSIVE

This is the 5.7 version of this patch. Tests needed to be rewritten
and source code is a little bit different, so null-merged from 5.6 and
created a new changeset (this one) for 5.7.

Background:

In 5.6, GTID_MODE can only take two values: ON and OFF. In 5.7,
GTID_MODE can take four values: ON, ON_PERMISSIVE, OFF_PERMISSIVE, and
OFF. A 5.7 master should be able to replicate to a 5.6 slave if master
uses X_PERMISSIVE and slave uses X.

Problem:

Due to a sanity check on the slave where the slave explicitly checks
the master's GTID_MODE, the slave refuses to start replication.

The 5.6 server was actually prepared to handle the new modes
introduced by 5.7, but in the end the names of the modes were changed:
5.6 allows a master to have modes UPGRADE_STEP_1 and UPGRADE_STEP_2
but not ON_PERMISSIVE or OFF_PERMISSIVE.

Fix:

- Allow slave to replicate if the master's GTID_MODE *begins* with ON
  or OFF. The slave in this case will ignore the remainder of the
  GTID_MODE string and treat master as being ON or OFF.

- Report a warning if the master's GTID_MODE begins with ON or OFF but
  is not equal to ON or OFF.

@sql/rpl_slave.cc
- Allow master's GTID_MODE to be any string that begins with ON or
  OFF.
- Report a warning if the master's GTID_MODE begins with ON or OFF but
  is not equal to ON or OFF.

@mysql-test/include/assert_grep.inc
- Improve debug info.

@mysql-test/suite/rpl/t/rpl_gtid_mode.test
- In 5.7, this is a more appropriate place for the test.  Also, the
  test is rewritten to avoid server restarts since restarts are not
  needed in 5.7. Also removed the .opt file for the test.

Author: Sven Sandberg

mysql-test/include/assert_grep.inc

@@ -48,7 +48,7 @@ if (!$assert_text)
 }
 if (!$assert_file)
 {
-  --die !!!ERROR IN TEST: you must set $file
+  --die !!!ERROR IN TEST: you must set $assert_file
 }
 if (!$assert_select)
 {
@@ -132,8 +132,12 @@ if ($_ag_outcome != 'assert_grep.inc ok')
 {
   --source include/show_rpl_debug_info.inc
   --echo include/assert_grep.inc failed!
+  --echo assert_text: '$assert_text'
+  --echo assert_file: '$assert_file'
   --echo assert_select: '$assert_select'
   --echo assert_match: '$assert_match'
+  --echo assert_count: '$assert_count'
+  --echo assert_only_after: '$assert_only_after'
   if ($assert_match != '')
   {
     --echo matching lines: '$_ag_outcome'

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

@@ -6,6 +6,19 @@ Note	####	Storing MySQL user name or password information in the master info rep
 ==== Initialize ====
 call mtr.add_suppression("Slave I/O for channel '': The replication receiver thread cannot start");
 call mtr.add_suppression("Slave I/O for channel '': The slave IO thread stops");
+call mtr.add_suppression("Slave I/O for channel '': Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF");
+call mtr.add_suppression("GTID_LOG_EVENT or ANONYMOUS_GTID_LOG_EVENT is not expected in an event stream after a GTID_LOG_EVENT or an ANONYMOUS_GTID_LOG_EVENT.");
+call mtr.add_suppression("An unexpected event sequence was detected by the IO thread while queuing the event received from master");
+call mtr.add_suppression("Detected misconfiguration: replication channel '' was configured with AUTO_POSITION = 1, but the server was started with --gtid-mode=off.");
+call mtr.add_suppression("Slave I/O for channel '': Relay log write failure: could not queue event from master");
+call mtr.add_suppression("Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate anonymous transaction when AUTO_POSITION = 1");
+call mtr.add_suppression("Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate anonymous transaction when AUTO_POSITION = 1,");
+call mtr.add_suppression("Slave I/O for channel '': The master uses an unknown GTID_MODE 'on_something'. Treating it as 'ON'.");
+call mtr.add_suppression("Slave I/O for channel '': The master uses an unknown GTID_MODE 'off_something'. Treating it as 'OFF'.");
+call mtr.add_suppression("Could not open .* for logging.*. Turning logging off for the whole duration of the MySQL server process.");
 include/sync_slave_sql_with_master.inc
 include/stop_slave.inc
 ==== Checks performed at server start ====
@@ -160,6 +173,7 @@ include/rpl_set_gtid_mode.inc [OFF on servers 1,2]
 START SLAVE IO_THREAD;
 include/wait_for_slave_io_error.inc [errno=1236  # ER_CANT_REPLICATE_GTID_WITH_GTID_MODE_OFF]
 include/assert.inc [sender thread should report - Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF.]
+include/assert_grep.inc [Receiver thread should report - Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF.]
 [connection master]
 DROP TABLE t1;
 RESET MASTER;
@@ -213,6 +227,7 @@ include/rpl_set_gtid_mode.inc [ON on servers 1,2]
 START SLAVE IO_THREAD;
 include/wait_for_slave_io_error.inc [errno=1236 # ER_CANT_REPLICATE_ANONYMOUS_WITH_GTID_MODE_ON]
 include/assert.inc [sender thread should report - Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON.]
+include/assert_grep.inc [While gtid-mode=on, slave expects an anonymous event to get ER_CANT_REPLICATE_ANONYMOUS_WITH_GTID_MODE_ON.]
 [connection master]
 DROP TABLE t3;
 include/rpl_reset.inc
@@ -261,6 +276,7 @@ CHANGE MASTER TO MASTER_AUTO_POSITION= 1;
 START SLAVE IO_THREAD;
 include/wait_for_slave_io_error.inc [errno=1236 # ER_CANT_REPLICATE_ANONYMOUS_WITH_AUTO_POSITION]
 include/assert.inc [sender thread should report - Cannot replicate anonymous transaction when AUTO_POSITION = 1.]
+include/assert_grep.inc [While AUTO_POSITION is enabled, Master sends an anonymous transaction resulting into ER_CANT_REPLICATE_ANONYMOUS_WITH_AUTO_POSITION.]
 include/rpl_restart_server.inc [server_number=1 gtids=off]
 [connection master]
 SET GLOBAL ENFORCE_GTID_CONSISTENCY = ON;
@@ -353,20 +369,33 @@ include/rpl_set_gtid_mode.inc [OFF on servers 1]
 include/stop_slave.inc
 Warnings:
 Note	3084	Replication thread(s) for channel '' are already stopped.
+RESET SLAVE;
 SET @@GLOBAL.DEBUG= 'd,simulate_master_has_unknown_gtid_mode';
 START SLAVE IO_THREAD;
 include/wait_for_slave_io_error.inc [errno=1593]
 Warnings:
 Warning	3090	Changing sql mode 'NO_AUTO_CREATE_USER' is deprecated. It will be removed in a future release.
-Last_IO_Error = 'The slave IO thread stops because the master has an unknown @@GLOBAL.GTID_MODE.'
+Last_IO_Error = 'The slave IO thread stops because the master has an unknown @@GLOBAL.GTID_MODE 'Krakel Spektakel'.'
 Warnings:
 Warning	3090	Changing sql mode 'NO_AUTO_CREATE_USER' is deprecated. It will be removed in a future release.
 SET @@GLOBAL.DEBUG= @debug_saved;
+#
+# Warning generated if master has unknown gtid_mode that begins
+# with ON or OFF.
+#
+SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE;
+SET @@GLOBAL.DEBUG = 'd,simulate_master_has_gtid_mode_on_something';
+include/start_slave.inc
+include/assert_grep.inc [Receiver thread should report that on_something is unknown]
+include/stop_slave.inc
+SET @@GLOBAL.DEBUG = 'd,simulate_master_has_gtid_mode_off_something';
+include/start_slave.inc
+include/assert_grep.inc [Receiver thread should report that off_something is unknown]
+include/stop_slave.inc
 RESET SLAVE;
 #
 # ER_CANT_SET_GTID_MODE generated because AUTO_POSITION = 1.
 #
-SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE;
 include/rpl_set_gtid_mode.inc [ON on servers 1]
 CHANGE MASTER TO MASTER_AUTO_POSITION = 1;
 SET @@GLOBAL.GTID_MODE = OFF;

mysql-test/suite/rpl/t/rpl_gtid_mode-slave.opt

@@ -48,6 +48,20 @@
 
 call mtr.add_suppression("Slave I/O for channel '': The replication receiver thread cannot start");
 call mtr.add_suppression("Slave I/O for channel '': The slave IO thread stops");
+call mtr.add_suppression("Slave I/O for channel '': Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF");
+call mtr.add_suppression("GTID_LOG_EVENT or ANONYMOUS_GTID_LOG_EVENT is not expected in an event stream after a GTID_LOG_EVENT or an ANONYMOUS_GTID_LOG_EVENT.");
+call mtr.add_suppression("An unexpected event sequence was detected by the IO thread while queuing the event received from master");
+call mtr.add_suppression("Detected misconfiguration: replication channel '' was configured with AUTO_POSITION = 1, but the server was started with --gtid-mode=off.");
+call mtr.add_suppression("Slave I/O for channel '': Relay log write failure: could not queue event from master");
+call mtr.add_suppression("Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON");
+call mtr.add_suppression("Slave I/O for channel '': Cannot replicate anonymous transaction when AUTO_POSITION = 1");
+call mtr.add_suppression("Got fatal error 1236 from master when reading data from binary log: 'Cannot replicate anonymous transaction when AUTO_POSITION = 1,");
+call mtr.add_suppression("Slave I/O for channel '': The master uses an unknown GTID_MODE 'on_something'. Treating it as 'ON'.");
+call mtr.add_suppression("Slave I/O for channel '': The master uses an unknown GTID_MODE 'off_something'. Treating it as 'OFF'.");
+call mtr.add_suppression("Could not open .* for logging.*. Turning logging off for the whole duration of the MySQL server process.");
+
 --let $saved_binlog_error_action=`SELECT @@GLOBAL.binlog_error_action`
 
 --source include/sync_slave_sql_with_master.inc
@@ -57,9 +71,9 @@ call mtr.add_suppression("Slave I/O for channel '': The slave IO thread stops");
 --connection master
 --let $saved_innodb_page_size_server1=`SELECT @@innodb_page_size`
 
---let $server1_cmd= $MYSQLD --defaults-group-suffix=.1 --defaults-file=$MYSQLTEST_VARDIR/my.cnf --log-output=file --default-storage-engine=InnoDB --default-tmp-storage-engine=InnoDB --innodb-page-size=$saved_innodb_page_size_server1
+--let $server1_cmd= $MYSQLD --defaults-group-suffix=.1 --defaults-file=$MYSQLTEST_VARDIR/my.cnf --default-storage-engine=InnoDB --default-tmp-storage-engine=InnoDB --innodb-page-size=$saved_innodb_page_size_server1
 
---let $server2_cmd= $MYSQLD --defaults-group-suffix=.2 --defaults-file=$MYSQLTEST_VARDIR/my.cnf --log-output=file --default-storage-engine=InnoDB --default-tmp-storage-engine=InnoDB --innodb-page-size=$saved_innodb_page_size_server2
+--let $server2_cmd= $MYSQLD --defaults-group-suffix=.2 --defaults-file=$MYSQLTEST_VARDIR/my.cnf --default-storage-engine=InnoDB --default-tmp-storage-engine=InnoDB --innodb-page-size=$saved_innodb_page_size_server2
 
 --echo ==== Checks performed at server start ====
 
@@ -225,6 +239,13 @@ START SLAVE IO_THREAD;
 --let $assert_cond= COUNT(*) = 1 FROM performance_schema.replication_connection_status WHERE LAST_ERROR_MESSAGE LIKE "%Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF%";
 --source include/assert.inc
 
+--let $assert_text= Receiver thread should report - Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF.
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
+--let $assert_select= Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF
+--let $assert_only_after= Slave I/O thread for channel '': connected to master
+--let $assert_count= 2
+--source include/assert_grep.inc
+
 --source include/rpl_connection_master.inc
 DROP TABLE t1;
 
@@ -262,9 +283,10 @@ CREATE TABLE t2(a int);
 --source include/wait_for_slave_io_error.inc
 
 --let $assert_text= Receiver thread should report - Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF.
---let $assert_file= $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
 --let $assert_select= Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF
---let $assert_count= 3
+--let $assert_only_after= Slave I/O thread for channel '': connected to master
+--let $assert_count= 1
 --source include/assert_grep.inc
 
 --source include/rpl_connection_master.inc
@@ -298,7 +320,7 @@ CHANGE MASTER TO MASTER_AUTO_POSITION= 1;
 SET GLOBAL ENFORCE_GTID_CONSISTENCY = ON;
 
 --let $assert_text= While AUTO_POSITION is set, attempt to restart the slave with gtid-mode= off to get ER_STARTING_WITH_GTID_MODE_OFF_AND_AUTO_POSITION.
---let $assert_file= $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
 --let $assert_select= Detected misconfiguration: replication channel '' was configured with AUTO_POSITION = 1, but the server was started with --gtid-mode=off
 --let $assert_count= 1
 --source include/assert_grep.inc
@@ -345,6 +367,13 @@ START SLAVE IO_THREAD;
 --let $assert_cond= COUNT(*) = 1 FROM performance_schema.replication_connection_status WHERE LAST_ERROR_MESSAGE LIKE "%Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON%";
 --source include/assert.inc
 
+--let $assert_text= While gtid-mode=on, slave expects an anonymous event to get ER_CANT_REPLICATE_ANONYMOUS_WITH_GTID_MODE_ON.
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
+--let $assert_select= Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON
+--let $assert_only_after= Slave I/O thread for channel '': connected to master
+--let $assert_count= 2
+--source include/assert_grep.inc
+
 --source include/rpl_connection_master.inc
 DROP TABLE t3;
 
@@ -367,9 +396,10 @@ CREATE TABLE t4(a int);
 --source include/wait_for_slave_io_error.inc
 
 --let $assert_text= While gtid-mode=on, slave expects an anonymous event to get ER_CANT_REPLICATE_ANONYMOUS_WITH_GTID_MODE_ON.
---let $assert_file= $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
 --let $assert_select= Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON
---let $assert_count= 3
+--let $assert_only_after= Slave I/O thread for channel '': connected to master
+--let $assert_count= 1
 --source include/assert_grep.inc
 
 --source include/stop_slave_sql.inc
@@ -443,6 +473,12 @@ START SLAVE IO_THREAD;
 --let $assert_cond= COUNT(*) = 1 FROM performance_schema.replication_connection_status WHERE LAST_ERROR_MESSAGE LIKE "%Cannot replicate anonymous transaction when AUTO_POSITION = 1%";
 --source include/assert.inc
 
+--let $assert_text= While AUTO_POSITION is enabled, Master sends an anonymous transaction resulting into ER_CANT_REPLICATE_ANONYMOUS_WITH_AUTO_POSITION.
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
+--let $assert_select= Cannot replicate anonymous transaction when AUTO_POSITION = 1
+--let $assert_count= 1
+--source include/assert_grep.inc
+
 --let $rpl_server_number=1
 --let $rpl_start_with_gtids= 0
 --source include/rpl_restart_server.inc
@@ -523,9 +559,9 @@ START SLAVE IO_THREAD;
 --source include/wait_for_slave_io_error.inc
 
 --let $assert_text= While AUTO_POSITION is enabled, Master sends an anonymous transaction resulting into ER_CANT_REPLICATE_ANONYMOUS_WITH_AUTO_POSITION.
---let $assert_file= $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
+--let $assert_file= $MYSQLTEST_VARDIR/log/mysqld.2.err
 --let $assert_select= Cannot replicate anonymous transaction when AUTO_POSITION = 1
---let $assert_count= 2
+--let $assert_count= 1
 --source include/assert_grep.inc
 
 --source include/rpl_connection_slave.inc
@@ -603,37 +639,61 @@ INSERT INTO t7 values (1);
 
 SET GTID_NEXT='AUTOMATIC';
 DROP TABLE t7;
-RESET MASTER;
 
+RESET MASTER;
 --let $rpl_server_numbers= 1
 --let $rpl_skip_sync= 1
 --let $rpl_gtid_mode= OFF
 --source include/rpl_set_gtid_mode.inc
 
+
 # Get rid of the manually generated slave error log file.
---remove_file $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
+#--remove_file $MYSQLTEST_VARDIR/tmp/slave-rpl-gtid-mode.err
 
 --echo #
 --echo # Error generated if master has an unknown gtid_mode
 --echo #
 
 --connection slave
 --source include/stop_slave.inc
+RESET SLAVE;
 SET @@GLOBAL.DEBUG= 'd,simulate_master_has_unknown_gtid_mode';
 START SLAVE IO_THREAD;
 --let $slave_io_errno= convert_error(ER_SLAVE_FATAL_ERROR)
 --let $show_slave_io_error= 1
 --source include/wait_for_slave_io_error.inc
 SET @@GLOBAL.DEBUG= @debug_saved;
 
+--echo #
+--echo # Warning generated if master has unknown gtid_mode that begins
+--echo # with ON or OFF.
+--echo #
+
+SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE;
+
+SET @@GLOBAL.DEBUG = 'd,simulate_master_has_gtid_mode_on_something';
+--source include/start_slave.inc
+--let $assert_file=$MYSQLTEST_VARDIR/log/mysqld.2.err
+--let $assert_count= 1
+--let $assert_only_after= Slave I/O thread for channel '': connected to master
+--let $assert_text= Receiver thread should report that on_something is unknown
+--let $assert_select= Slave I/O for channel '': The master uses an unknown GTID_MODE 'on_something'. Treating it as 'ON'.
+--source include/assert_grep.inc
+
+--source include/stop_slave.inc
+SET @@GLOBAL.DEBUG = 'd,simulate_master_has_gtid_mode_off_something';
+--source include/start_slave.inc
+--let $assert_text= Receiver thread should report that off_something is unknown
+--let $assert_select= Slave I/O for channel '': The master uses an unknown GTID_MODE 'off_something'. Treating it as 'OFF'.
+--source include/assert_grep.inc
+
+--source include/stop_slave.inc
 RESET SLAVE;
 
 --echo #
 --echo # ER_CANT_SET_GTID_MODE generated because AUTO_POSITION = 1.
 --echo #
 
-SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE;
-
 --let $rpl_server_numbers= 1
 --let $rpl_gtid_mode= ON
 --let $rpl_skip_sync= 1

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

@@ -15,6 +15,10 @@ SET @@global.enforce_gtid_consistency = ON;
 select @@global.gtid_mode;
 --error ER_INCORRECT_GLOBAL_LOCAL_VAR
 select @@session.gtid_mode;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+set gtid_mode = @start_global_value;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+set @@session.gtid_mode = @start_global_value;
 show global variables like 'gtid_mode';
 show session variables like 'gtid_mode';
 --disable_warnings

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

@@ -2321,6 +2321,25 @@ static int get_master_uuid(MYSQL *mysql, Master_info *mi)
   return ret;
 }
 
+
+/**
+  Determine, case-sensitively, if short_string is equal to
+  long_string, or a true prefix of long_string, or not a prefix.
+
+  @retval 0 short_string is not a prefix of long_string.
+  @retval 1 short_string is a true prefix of long_string (not equal).
+  @retval 2 short_string is equal to long_string.
+*/
+static int is_str_prefix_case(const char *short_string, const char *long_string)
+{
+  int i;
+  for (i= 0; short_string[i]; i++)
+    if (my_toupper(system_charset_info, short_string[i]) !=
+        my_toupper(system_charset_info, long_string[i]))
+      return 0;
+  return long_string[i] ? 1 : 2;
+}
+
 /*
   Note that we rely on the master's version (3.23, 4.0.14 etc) instead of
   relying on the binlog's version. This is not perfect: imagine an upgrade
@@ -2896,17 +2915,51 @@ when it try to get the value of TIME_ZONE global variable from master.";
     {
       bool error= false;
       const char *master_gtid_mode_string= master_row[0];
+      DBUG_EXECUTE_IF("simulate_master_has_gtid_mode_on_something",
+                      { master_gtid_mode_string= "on_something"; });
+      DBUG_EXECUTE_IF("simulate_master_has_gtid_mode_off_something",
+                      { master_gtid_mode_string= "off_something"; });
       DBUG_EXECUTE_IF("simulate_master_has_unknown_gtid_mode",
                       { master_gtid_mode_string= "Krakel Spektakel"; });
       master_gtid_mode= get_gtid_mode(master_gtid_mode_string, &error);
-      mysql_free_result(master_res);
+      if (error)
+      {
+        // For potential future compatibility, allow unknown
+        // GTID_MODEs that begin with ON/OFF (treating them as ON/OFF
+        // respectively).
+        enum_gtid_mode mode= GTID_MODE_OFF;
+        for (int i= 0; i < 2; i++)
+        {
+          switch (is_str_prefix_case(get_gtid_mode_string(mode),
+                                     master_gtid_mode_string))
+          {
+          case 0: // is not a prefix; continue loop
+            break;
+          case 1: // is a true prefix, i.e. not equal
+            mi->report(WARNING_LEVEL, ER_UNKNOWN_ERROR,
+                       "The master uses an unknown GTID_MODE '%s'. "
+                       "Treating it as '%s'.",
+                       master_gtid_mode_string,
+                       get_gtid_mode_string(mode));
+            // fall through
+          case 2: // is equal
+            error= false;
+            master_gtid_mode= mode;
+            break;
+          }
+          mode= GTID_MODE_ON;
+        }
+      }
       if (error)
       {
         mi->report(ERROR_LEVEL, ER_SLAVE_FATAL_ERROR,
                    "The slave IO thread stops because the master has "
-                   "an unknown @@GLOBAL.GTID_MODE.");
+                   "an unknown @@GLOBAL.GTID_MODE '%s'.",
+                   master_gtid_mode_string);
+        mysql_free_result(master_res);
         DBUG_RETURN(1);
       }
+      mysql_free_result(master_res);
       break;
     }
     }