I have a mysql5.0 server that is very slow authenticating database requests. After a just a few requests there is a backlog of processes, showing waiting for login:
| Id | User | Host | db | Command | Time | State | Info |
+----+----------------------+--------------------+------+---------+------+-------+------------------+
| 1 | root | 192.168.1.15:51725 | ouw | Query | 0 | NULL | show processlist |
| 13 | unauthenticated user | 192.168.1.4:47782 | NULL | Connect | NULL | login | NULL |
| 14 | unauthenticated user | 192.168.1.4:47783 | NULL | Connect | NULL | login | NULL |
| 15 | unauthenticated user | 192.168.1.4:47784 | NULL | Connect | NULL | login | NULL |
| 16 | unauthenticated user | 192.168.1.4:47785 | NULL | Connect | NULL | login | NULL |
| 17 | unauthenticated user | 192.168.1.4:47786 | NULL | Connect | NULL | login | NULL |
| 18 | unauthenticated user | 192.168.1.4:47787 | NULL | Connect | NULL | login | NULL |
| 19 | unauthenticated user | 192.168.1.4:47788 | NULL | Connect | NULL | login | NULL |
| 20 | unauthenticated user | 192.168.1.4:47789 | NULL | Connect | NULL | login | NULL |
| 21 | unauthenticated user | 192.168.1.4:47790 | NULL | Connect | NULL | login | NULL |
| 22 | unauthenticated user | 192.168.1.4:47791 | NULL | Connect | NULL | login | NULL |
| 23 | unauthenticated user | 192.168.1.4:47792 | NULL | Connect | NULL | login | NULL |
| 24 | unauthenticated user | 192.168.1.4:38101 | NULL | Connect | NULL | login | NULL |
| 25 | unauthenticated user | 192.168.1.4:38102 | NULL | Connect | NULL | login | NULL |
| 26 | unauthenticated user | 192.168.1.4:38103 | NULL | Connect | NULL | login | NULL |
| 27 | unauthenticated user | 192.168.1.4:38104 | NULL | Connect | NULL | login | NULL |
| 28 | unauthenticated user | 192.168.1.4:38105 | NULL | Connect | NULL | login | NULL |
...
and so on. The earliest connections get slowly dropped, but if there are many connections they requestors eventually time out. The processlist entries stay in the table for quite a while. It is as if only one thread can authenticate at a time.
The server had crashed and was restarted. I double-checked the database credentials and ran myisamchk -f against the mysql and wordpress databases. (no errors other than improperly closed tables)
What could cause this slowdown?