Bug #84065 innodb_monitor_enable and innodb_monitor_disable do not clear each other
Submitted: 5 Dec 2016 22:41 Modified: 6 Dec 2016 11:36
Reporter: Bradley Mickel Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: InnoDB storage engine Severity:S3 (Non-critical)
Version:5.6/5.7/8.0 OS:Any
Assigned to: CPU Architecture:Any

[5 Dec 2016 22:41] Bradley Mickel
Description:
When updating the global variables the previous item is not adjusted, so they both may say 'all'.

select @@version, @@innodb_monitor_enable, @@innodb_monitor_disable;
+------------+-------------------------+--------------------------+
| @@version  | @@innodb_monitor_enable | @@innodb_monitor_disable |
+------------+-------------------------+--------------------------+
| 5.6.28-log | all                     | all                      |
+------------+-------------------------+--------------------------+

Without going to the status field of the INFORMATION_SCHEMA.INNODB_METRICS table there is no way to know which variable is correct. Whichever was updated last will take precedence.

How to repeat:
db2 (none)> set global innodb_monitor_disable='all';
Query OK, 0 rows affected (0.00 sec)

db2 (none)>set global innodb_monitor_enable='all';
Query OK, 0 rows affected (0.00 sec)

db2 (none)>select @@innodb_monitor_enable, @@innodb_monitor_disable;

+-------------------------+--------------------------+
| @@innodb_monitor_enable | @@innodb_monitor_disable |
+-------------------------+--------------------------+
| all                     | all                      |
+-------------------------+--------------------------+
1 row in set (0.00 sec)

db2 (none)>select distinct status from INFORMATION_SCHEMA.INNODB_METRICS;

+---------+
| status  |
+---------+
| enabled |
+---------+
1 row in set (0.01 sec)

db2 (none)> set global innodb_monitor_disable='all';
Query OK, 0 rows affected (0.00 sec)

db2 (none)>select @@innodb_monitor_enable, @@innodb_monitor_disable;

+-------------------------+--------------------------+
| @@innodb_monitor_enable | @@innodb_monitor_disable |
+-------------------------+--------------------------+
| all                     | all                      |
+-------------------------+--------------------------+
1 row in set (0.00 sec)

db2 (none)>select distinct status from INFORMATION_SCHEMA.INNODB_METRICS;

+---------+
| status  |
+---------+
| disabled |
+---------+
1 row in set (0.01 sec)

Suggested fix:
When updating one of the variables to all, if the same thing is in the other variable then set it to NULL
[6 Dec 2016 11:36] Miguel Solorzano
Thank you for the bug report. Verified as described.