Plugin kills server due to 60 simultaneous db backups

My server just ground to a halt and when I looked at the process list, I saw over 60 mysqldump + gzip commands issued by WP-DBManager, all running at the same time. The load was over 100.

I don’t know how it’s happened, but if the plugin doesn’t use semaphores of sorts to make sure only 1 backup is happening at the same time, multiple wp-cron calls are apparently launching tons of backups, which then end up wiping each other because of the “keep last 10 backups” file limit.

Have a look:

ps -ef | grep gzip | grep mysqldump | wc
     63    1260   19467

No. 	Database File 	Date/Time 	Size 	Select
1	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	0 bytes
2	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	320.0 KiB
3	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	288.0 KiB
4	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	624.0 KiB
5	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	816.0 KiB
6	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	1.2 MiB
7	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	1.3 MiB
8	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:02 pm	1.5 MiB
9	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:01 pm	1.7 MiB
10	androidpolice_com_wp.sql.gz	May 21, 2011 @ 4:01 pm	1.7 MiB
10 Backup Files 	9.3 MiB

wp-content/backup-db> l
total 8320
drwxrwxr-x  2 archon810 www    4096 2011-05-21 15:55 ./
drwxrwxr-x 10 archon810 www    4096 2011-05-20 15:41 ../
-rw-r--r--  1 wwwrun    www 1605632 2011-05-21 15:55 1305993297_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1441792 2011-05-21 15:55 1305993300_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1245184 2011-05-21 15:55 1305993302_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1081344 2011-05-21 15:55 1305993305_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  933888 2011-05-21 15:55 1305993306_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  688128 2011-05-21 15:55 1305993309_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  606208 2011-05-21 15:55 1305993310_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  491520 2011-05-21 15:55 1305993311_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  376832 2011-05-21 15:55 1305993313_-_androidpolice_com_wp.sql.gz
-rwxr--r--  1 archon810 www      58 2010-03-05 23:26 .htaccess*
wp-content/backup-db> l
total 9664
drwxrwxr-x  2 archon810 www    4096 2011-05-21 15:59 ./
drwxrwxr-x 10 archon810 www    4096 2011-05-20 15:41 ../
-rw-r--r--  1 wwwrun    www 2244608 2011-05-21 15:59 1305993545_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1605632 2011-05-21 15:59 1305993555_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1409024 2011-05-21 15:59 1305993558_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www 1196032 2011-05-21 15:59 1305993560_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  966656 2011-05-21 15:59 1305993564_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  917504 2011-05-21 15:59 1305993565_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  786432 2011-05-21 15:59 1305993566_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  507904 2011-05-21 15:59 1305993569_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www  163840 2011-05-21 15:59 1305993573_-_androidpolice_com_wp.sql.gz
-rw-r--r--  1 wwwrun    www   49152 2011-05-21 15:59 1305993575_-_androidpolice_com_wp.sql.gz
-rwxr--r--  1 archon810 www      58 2010-03-05 23:26 .htaccess*

This is a huge problem – I’ve disabled the plugin for now. Will probably move to doing my own backups from now on.