Mathias Meyer
Mathias Meyer

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If you ever see a list like this in your MySQL process list, run!

+---------+--------------------------------------------+--------------------------------+------------+-----------------+------------+-------------+------------+
| Id  | User                 | Host           | db   | Command | Time | State | Info |
+---------+--------------------------------------------+--------------------------------+------------+-----------------+------------+-------------+------------+
| 442 | unauthenticated user | 10.1.1.2:55885 | NULL | Killed  | NULL | login | NULL | 
| 443 | unauthenticated user | 10.1.1.1:48009 | NULL | Killed  | NULL | login | NULL | 
.....
| 444 | unauthenticated user | 10.1.1.1:58105 | NULL | Killed  | NULL | login | NULL | 
| 445 | unauthenticated user | 10.1.1.2:60799 | NULL | Killed  | NULL | login | NULL | 
+---------+--------------------------------------------+--------------------------------+------------+-----------------+------------+-------------+------------+

No seriously. Apparently it’s something of a known bug which comes up at unpredictable points in time.

One proposed solution is to add all your internal hosts which can’t be looked up through DNS to your /etc/hosts file:

10.1.1.1    appserver1
10.1.1.2    appserver2

Et voila. The exact same moment, all the users were authenticated. Scary? Yes. Weird? Yes. Problem solved? Yes.