BUG#29899128: GR_CONSISTENT_READS_LOWER_VERSION FAILS SPORADICALLY

The test validates the behavior of Group Replication consistency
guarantees when the group contains members of lower versions that do
not know the consistency guarantees.
The lower version members are being emulated by the use of
group_replication_force_lower_version_on_group_replication_consistency
debug flag.

The debug flag was being unset too soon, that is, before the remote
member handled the transaction with consistency guarantee, which was
causing the test to fail with unexpected behaviour.

Fixed by adding a synchronization point that ensures that all
transactions with consistency guarantees are handled before the
debug flag is unset.

ReviewBoard: 22411

Author: nacarvalho

mysql-test/suite/group_replication/r/gr_consistent_reads_lower_version.result

@@ -33,14 +33,11 @@ ERROR 40000: Plugin instructed the server to rollback the current transaction.
 SET @@SESSION.group_replication_consistency= 'BEFORE_AND_AFTER';
 INSERT INTO t1 VALUES (3);
 ERROR 40000: Plugin instructed the server to rollback the current transaction.
-SET @@SESSION.group_replication_consistency= DEFAULT;
-[connection server1]
-SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
-[connection server2]
-SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
 
 ############################################################
 # 06. Validate data.
+SET @@SESSION.group_replication_consistency= DEFAULT;
+INSERT INTO t1 VALUES (0);
 include/rpl_sync.inc
 [connection server1]
 include/assert.inc ['1 exists in table t1']
@@ -55,4 +52,7 @@ include/assert.inc ['3 does not exist in table t1']
 # 07. Clean up.
 [connection server1]
 DROP TABLE t1;
+SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
+[connection server2]
+SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
 include/group_replication_end.inc

mysql-test/suite/group_replication/t/gr_consistent_reads_lower_version.test

@@ -61,21 +61,15 @@ SET @@SESSION.group_replication_consistency= 'BEFORE_AND_AFTER';
 --error ER_TRANSACTION_ROLLBACK_DURING_COMMIT
 INSERT INTO t1 VALUES (3);
 
-SET @@SESSION.group_replication_consistency= DEFAULT;
-
---let $rpl_connection_name= server1
---source include/rpl_connection.inc
-SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
-
---let $rpl_connection_name= server2
---source include/rpl_connection.inc
-SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
-
 
 --echo
 --echo ############################################################
 --echo # 06. Validate data.
+# Wait until server1 applier handles all transactions.
+SET @@SESSION.group_replication_consistency= DEFAULT;
+INSERT INTO t1 VALUES (0);
 --source include/rpl_sync.inc
+
 --let $rpl_connection_name= server1
 --source include/rpl_connection.inc
 
@@ -113,5 +107,10 @@ SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replicati
 --let $rpl_connection_name= server1
 --source include/rpl_connection.inc
 DROP TABLE t1;
+SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
+
+--let $rpl_connection_name= server2
+--source include/rpl_connection.inc
+SET @@GLOBAL.DEBUG= '-d,group_replication_force_lower_version_on_group_replication_consistency';
 
 --source include/group_replication_end.inc