MDEV-27760 event may non stop replicate in circular semisync setup

MDEV-21117 had to relax own events acceptance condition for a case
when a former semisync master server recovers after crash as the
semisync slave. That however admitted a possibility for endless event
"orbiting" in the non-strict slave gtid mode of semisync circular
setup.

The same server-id event termination is restored now for
the non-strict gtid mode to follow regular rules (that is it's ignored
unless @@global.replicate_same_server_id allows it in).

To address MDEV-21117 recovery agenda,
in the strict gtid mode and the transaction's gtid ordered strictly
greater than the current slave gtid state, the same server-id
transaction is accepted.

The gtid strict mode is safe to accept transactions even if
the slave state were not set correct by the user, e.g
at the former master.
An added test shows a typical out-of-order error at execution so
no data corruption is guaranteed in such a case.

3 files changed, 202 insertions, 0 deletions

diff --git a/mysql-test/suite/rpl/r/rpl_circular_semi_sync.result b/mysql-test/suite/rpl/r/rpl_circular_semi_sync.result
new file mode 100644
index 00000000000..dcced9833ca
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_circular_semi_sync.result
@@ -0,0 +1,76 @@
+include/master-slave.inc
+[connection master]
+# Master server_1 and Slave server_2 initialiation ...
+connection server_2;
+include/stop_slave.inc
+connection server_1;
+set @@sql_log_bin = off;
+call mtr.add_suppression("Slave: An attempt was made to binlog GTID 10-1-1 which would create an out-of-order sequence number with existing GTID");
+set @@sql_log_bin = on;
+RESET MASTER;
+set @@session.gtid_domain_id=10;
+set @@global.rpl_semi_sync_master_enabled = 1;
+set @@global.rpl_semi_sync_master_wait_point=AFTER_SYNC;
+connection server_2;
+RESET MASTER;
+ALTER TABLE mysql.gtid_slave_pos ENGINE=InnoDB;
+set @@session.gtid_domain_id=20;
+set @@global.rpl_semi_sync_slave_enabled = 1;
+# a 1948 warning is expected
+set @@global.gtid_slave_pos = "";
+Warnings:
+Warning	1948	Specified value for @@gtid_slave_pos contains no value for replication domain 0. This conflicts with the binary log which contains GTID 0-2-1. If MASTER_GTID_POS=CURRENT_POS is used, the binlog position will override the new value of @@gtid_slave_pos
+CHANGE MASTER TO master_use_gtid= slave_pos;
+include/start_slave.inc
+# ... server_1 -> server_2 is set up
+connection server_1;
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=Innodb;
+INSERT INTO t1 VALUES (1);
+connection server_2;
+# Circular configuration server_2 -> server_1 initialiation ...
+connection server_1;
+# A. ... first when server_1 is in gtid strict mode...
+set @@global.gtid_strict_mode = true;
+set @@global.rpl_semi_sync_slave_enabled = 1;
+CHANGE MASTER TO master_host='127.0.0.1', master_port=$SERVER_MYPORT_2, master_user='root', master_use_gtid=SLAVE_POS;
+# ...  only for it to fail 'cos if its inconsistent (empty) slave's gtid state:
+SELECT @@global.gtid_slave_pos;
+@@global.gtid_slave_pos
+
+START SLAVE;
+include/wait_for_slave_sql_error.inc [errno=1950]
+# B. ... Resume on the circular setup with the server_id now in the non-strict mode ...
+set @@global.gtid_strict_mode = false;
+include/start_slave.inc
+# ... to have succeeded.
+connection server_2;
+INSERT INTO t1 VALUES (2);
+connection server_1;
+INSERT INTO t1 VALUES (3);
+connection server_2;
+# The gtid states on server_2 must be equal to ...
+SHOW VARIABLES LIKE 'gtid_binlog_pos';
+Variable_name	Value
+gtid_binlog_pos	0-2-1,10-1-3,20-2-1
+SHOW VARIABLES LIKE 'gtid_slave_pos';
+Variable_name	Value
+gtid_slave_pos	0-2-1,10-1-3,20-2-1
+connection server_1;
+# ... the gtid states on server_1
+SHOW VARIABLES LIKE 'gtid_slave_pos';
+Variable_name	Value
+gtid_slave_pos	0-2-1,10-1-3,20-2-1
+SHOW VARIABLES LIKE 'gtid_binlog_pos';
+Variable_name	Value
+gtid_binlog_pos	0-2-1,10-1-3,20-2-1
+# Cleanup
+connection server_1;
+include/stop_slave.inc
+set @@global.rpl_semi_sync_master_enabled = default;
+set @@global.rpl_semi_sync_slave_enabled = default;
+set @@global.rpl_semi_sync_master_wait_point=default;
+DROP TABLE t1;
+connection server_2;
+set @@global.rpl_semi_sync_master_enabled = default;
+set @@global.rpl_semi_sync_slave_enabled = default;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_circular_semi_sync.cnf b/mysql-test/suite/rpl/t/rpl_circular_semi_sync.cnf
new file mode 100644
index 00000000000..be39fea91d8
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_circular_semi_sync.cnf
@@ -0,0 +1,11 @@
+!include suite/rpl/rpl_1slave_base.cnf
+!include include/default_client.cnf
+
+
+[mysqld.1]
+log-slave-updates
+sync-binlog=1
+
+[mysqld.2]
+log-slave-updates
+sync-binlog=1
diff --git a/mysql-test/suite/rpl/t/rpl_circular_semi_sync.test b/mysql-test/suite/rpl/t/rpl_circular_semi_sync.test
new file mode 100644
index 00000000000..51fa5a242ea
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_circular_semi_sync.test
@@ -0,0 +1,115 @@
+# ==== References ====
+#
+# MDEV-27760 event may non stop replicate in circular semisync setup
+#
+--source include/have_innodb.inc
+--source include/have_binlog_format_row.inc
+--source include/master-slave.inc
+
+# The following tests prove
+# A. out-of-order gtid error when the stict gtid mode semisync slave
+#    receives the same server-id gtid event inconsistent
+#    (rpl_semi_sync_fail_over tests the consistent case) with its state;
+# B. in the non-strict mode the same server-id events remains ignored
+#    by default as usual.
+#
+--echo # Master server_1 and Slave server_2 initialiation ...
+--connection server_2
+--source include/stop_slave.inc
+
+# Initial master
+--connection server_1
+set @@sql_log_bin = off;
+call mtr.add_suppression("Slave: An attempt was made to binlog GTID 10-1-1 which would create an out-of-order sequence number with existing GTID");
+set @@sql_log_bin = on;
+
+RESET MASTER;
+
+set @@session.gtid_domain_id=10;
+
+set @@global.rpl_semi_sync_master_enabled = 1;
+set @@global.rpl_semi_sync_master_wait_point=AFTER_SYNC;
+
+--connection server_2
+RESET MASTER;
+ALTER TABLE mysql.gtid_slave_pos ENGINE=InnoDB;
+
+set @@session.gtid_domain_id=20;
+
+set @@global.rpl_semi_sync_slave_enabled = 1;
+--echo # a 1948 warning is expected
+set @@global.gtid_slave_pos = "";
+CHANGE MASTER TO master_use_gtid= slave_pos;
+--source include/start_slave.inc
+--echo # ... server_1 -> server_2 is set up
+
+--connection server_1
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=Innodb;
+INSERT INTO t1 VALUES (1);
+--save_master_pos
+
+--connection server_2
+--sync_with_master
+
+--echo # Circular configuration server_2 -> server_1 initialiation ...
+--connection server_1
+--echo # A. ... first when server_1 is in gtid strict mode...
+set @@global.gtid_strict_mode = true;
+set @@global.rpl_semi_sync_slave_enabled = 1;
+
+evalp CHANGE MASTER TO master_host='127.0.0.1', master_port=$SERVER_MYPORT_2, master_user='root', master_use_gtid=SLAVE_POS;
+
+--echo # ...  only for it to fail 'cos if its inconsistent (empty) slave's gtid state:
+SELECT @@global.gtid_slave_pos;
+START SLAVE;
+#  ER_GTID_STRICT_OUT_OF_ORDER
+--let $slave_sql_errno = 1950
+--source include/wait_for_slave_sql_error.inc
+
+--echo # B. ... Resume on the circular setup with the server_id now in the non-strict mode ...
+set @@global.gtid_strict_mode = false;
+--source include/start_slave.inc
+
+--echo # ... to have succeeded.
+
+--connection server_2
+INSERT INTO t1 VALUES (2);
+--save_master_pos
+
+--connection server_1
+--sync_with_master
+
+INSERT INTO t1 VALUES (3);
+--save_master_pos
+
+--connection server_2
+--sync_with_master
+--echo # The gtid states on server_2 must be equal to ...
+--let $wait_condition=select @@gtid_slave_pos=@@gtid_binlog_pos
+--source include/wait_condition.inc
+SHOW VARIABLES LIKE 'gtid_binlog_pos';
+SHOW VARIABLES LIKE 'gtid_slave_pos';
+
+--connection server_1
+--echo # ... the gtid states on server_1
+--let $wait_condition=select @@gtid_slave_pos=@@gtid_binlog_pos
+--source include/wait_condition.inc
+SHOW VARIABLES LIKE 'gtid_slave_pos';
+SHOW VARIABLES LIKE 'gtid_binlog_pos';
+
+--echo # Cleanup
+--connection server_1
+--source include/stop_slave.inc
+set @@global.rpl_semi_sync_master_enabled = default;
+set @@global.rpl_semi_sync_slave_enabled = default;
+set @@global.rpl_semi_sync_master_wait_point=default;
+
+DROP TABLE t1;
+--save_master_pos
+
+--connection server_2
+--sync_with_master
+set @@global.rpl_semi_sync_master_enabled = default;
+set @@global.rpl_semi_sync_slave_enabled = default;
+
+--source include/rpl_end.inc