MDEV-4473: mysql_binlog_send() starts sending events from wrong GTID position in some master failover scenarios

Suppose binlog file X has in its Gtid_list_event: 0-1-3,0-2-5, and suppose the
slave requests to start replicating after 0-1-3.

In this case the bug was that master would start sending events from the start
of X. This is wrong, because 0-2-4 and 0-2-5 are contained in X-1, and are
needed by the slave. So these events were lost.

On the other hand, if the slave requested 0-2-5, then it _is_ correct to start
sending from the beginning of binlog file X, because 0-2-5 is the last GTID
logged in earlier binlogs. The difference is that 0-2-5 is the last of the
GTIDs in the Gtid_list_event. The problem was that the code did not check that
the matched GTID was the last one in the list.

Fixed by checking if the gtid requested by slave that matches a gtid in the
Gtid_list_event is the last event for that domain in the list. If not, go back
to a prior binlog to ensure all needed events are sent to slave.

mysql-test/include/show_events.inc:
  Backport --let $binlog_file=LAST, used by MDEV-4473 test case.

3 files changed, 146 insertions, 0 deletions

diff --git a/mysql-test/suite/rpl/r/rpl_gtid_mdev4473.result b/mysql-test/suite/rpl/r/rpl_gtid_mdev4473.result
new file mode 100644
index 00000000000..1289bbb7e20
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_gtid_mdev4473.result
@@ -0,0 +1,57 @@
+include/rpl_init.inc [topology=1->2,1->3]
+create table t1 (n int);
+insert into t1 values (1);
+insert into t1 values (2);
+include/stop_slave.inc
+include/wait_for_slave_to_stop.inc
+include/stop_slave.inc
+include/wait_for_slave_to_stop.inc
+reset slave all;
+CHANGE MASTER TO master_host = '127.0.0.1', master_port = SERVER_MYPORT_2,
+master_user='root', MASTER_USE_GTID=1;
+include/start_slave.inc
+include/wait_for_slave_to_start.inc
+flush logs;
+insert into t1 values (3);
+insert into t1 values (4);
+flush logs;
+CHANGE MASTER TO master_host = '127.0.0.1', master_port = SERVER_MYPORT_2,
+MASTER_USE_GTID=1;
+include/start_slave.inc
+select * from t1 order by n;
+n
+1
+2
+3
+4
+show binary logs;
+Log_name	File_size
+master-bin.000001	#
+show binlog events in 'master-bin.000001' from <binlog_start>;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; create table t1 (n int)
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; insert into t1 values (1)
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; insert into t1 values (2)
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; insert into t1 values (3)
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; insert into t1 values (4)
+master-bin.000001	#	Query	#	#	COMMIT
+include/stop_slave.inc
+include/wait_for_slave_to_stop.inc
+reset slave all;
+CHANGE MASTER TO master_host = '127.0.0.1', master_port = SERVER_MYPORT_1,
+master_user = 'root', MASTER_USE_GTID=1;
+include/start_slave.inc
+include/stop_slave.inc
+CHANGE MASTER TO master_host = '127.0.0.1', master_port = SERVER_MYPORT_1,
+MASTER_USE_GTID=1;
+include/start_slave.inc
+drop table t1;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.cnf b/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.cnf
new file mode 100644
index 00000000000..4fe90e6a281
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.cnf
@@ -0,0 +1,18 @@
+!include ../my.cnf
+
+[mysqld.1]
+log-slave-updates
+loose-innodb
+
+[mysqld.2]
+log-slave-updates
+loose-innodb
+
+[mysqld.3]
+log-slave-updates
+loose-innodb
+
+[ENV]
+SERVER_MYPORT_3=		@mysqld.3.port
+SERVER_MYSOCK_3=		@mysqld.3.socket
+
diff --git a/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.test b/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.test
new file mode 100644
index 00000000000..549d11e9d1c
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_gtid_mdev4473.test
@@ -0,0 +1,71 @@
+--source include/have_innodb.inc
+--source include/have_binlog_format_mixed.inc
+
+--let $rpl_topology=1->2,1->3
+--source include/rpl_init.inc
+
+connection server_1;
+create table t1 (n int);
+insert into t1 values (1);
+insert into t1 values (2);
+save_master_pos;
+
+connection server_3;
+sync_with_master;
+source include/stop_slave.inc;
+source include/wait_for_slave_to_stop.inc;
+
+connection server_2;
+sync_with_master;
+source include/stop_slave.inc;
+source include/wait_for_slave_to_stop.inc;
+reset slave all;
+
+connection server_1;
+--replace_result $SERVER_MYPORT_2 SERVER_MYPORT_2
+eval CHANGE MASTER TO master_host = '127.0.0.1', master_port = $SERVER_MYPORT_2,
+     master_user='root', MASTER_USE_GTID=1;
+source include/start_slave.inc;
+source include/wait_for_slave_to_start.inc;
+
+connection server_2;
+flush logs;
+insert into t1 values (3);
+insert into t1 values (4);
+flush logs;
+save_master_pos;
+
+connection server_3;
+--replace_result $SERVER_MYPORT_2 SERVER_MYPORT_2
+eval CHANGE MASTER TO master_host = '127.0.0.1', master_port = $SERVER_MYPORT_2,
+     MASTER_USE_GTID=1;
+source include/start_slave.inc;
+sync_with_master;
+
+select * from t1 order by n;
+source include/show_binary_logs.inc;
+let $binlog_file=LAST;
+source include/show_binlog_events.inc;
+
+connection server_1;
+source include/stop_slave.inc;
+source include/wait_for_slave_to_stop.inc;
+reset slave all;
+
+connection server_2;
+--replace_result $SERVER_MYPORT_1 SERVER_MYPORT_1
+eval CHANGE MASTER TO master_host = '127.0.0.1', master_port = $SERVER_MYPORT_1,
+     master_user = 'root', MASTER_USE_GTID=1;
+source include/start_slave.inc;
+
+connection server_3;
+source include/stop_slave.inc;
+--replace_result $SERVER_MYPORT_1 SERVER_MYPORT_1
+eval CHANGE MASTER TO master_host = '127.0.0.1', master_port = $SERVER_MYPORT_1,
+     MASTER_USE_GTID=1;
+source include/start_slave.inc;
+
+connection server_1;
+drop table t1;
+
+--source include/rpl_end.inc