There is also IMHO wrong error when turning the desync to ON twice:
pxc2>show global variables like 'wsrep_desync';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wsrep_desync | OFF |
+---------------+-------+
1 row in set (0.00 sec)
pxc2>set global wsrep_desync=1;
Query OK, 0 rows affected (0.01 sec)
pxc2>set global wsrep_desync=1;
ERROR 1396 (HY000): Operation 'desync' failed for set global wsrep_desync=1
pxc2>show warnings;
+---------+------+---------------------------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------------------------+
| Warning | 1231 | 'wsrep_desync' is already ON. |
| Error | 1396 | Operation 'desync' failed for set global wsrep_desync=1 |
+---------+------+---------------------------------------------------------+
2 rows in set (0.00 sec)
But:
pxc2>set global wsrep_desync=0;
Query OK, 0 rows affected (0.00 sec)
There is also IMHO wrong error when turning the desync to ON twice:
pxc2>show global variables like 'wsrep_desync'; ------- --+---- ---+ ------- --+---- ---+ ------- --+---- ---+
+------
| Variable_name | Value |
+------
| wsrep_desync | OFF |
+------
1 row in set (0.00 sec)
pxc2>set global wsrep_desync=1;
Query OK, 0 rows affected (0.01 sec)
pxc2>set global wsrep_desync=1;
ERROR 1396 (HY000): Operation 'desync' failed for set global wsrep_desync=1
pxc2>show warnings; ---+--- ---+--- ------- ------- ------- ------- ------- ------- ------- -----+ ---+--- ---+--- ------- ------- ------- ------- ------- ------- ------- -----+ ---+--- ---+--- ------- ------- ------- ------- ------- ------- ------- -----+
+------
| Level | Code | Message |
+------
| Warning | 1231 | 'wsrep_desync' is already ON. |
| Error | 1396 | Operation 'desync' failed for set global wsrep_desync=1 |
+------
2 rows in set (0.00 sec)
But:
pxc2>set global wsrep_desync=0;
Query OK, 0 rows affected (0.00 sec)
pxc2>set global wsrep_desync=0;
Query OK, 0 rows affected, 1 warning (0.00 sec)
pxc2>show warnings; ---+--- ---+--- ------- ------- ------- ------- -+ ---+--- ---+--- ------- ------- ------- ------- -+ ---+--- ---+--- ------- ------- ------- ------- -+
+------
| Level | Code | Message |
+------
| Warning | 1231 | 'wsrep_desync' is already OFF. |
+------
1 row in set (0.00 sec)
Tested on both PXC 5.5 and 5.6.