MythTV settings reset due to database problems

A couple of days ago I started getting wrong language EIT data – and therefore a lot of missed recordings (because the program titles had changed). This seemed very strange, because I had been getting correct EIT language data for over two months since the setup.

I then started investigating a bit more and noticed that ‘ISO639Language0’ and ‘ISO639Language1’ settings had been reset back to ‘eng’ (from ‘fin’). This seemed strange, so I started digging in my DB backups and was able to pinpoint a date when this reset had occurred. Then I looked at mythconverg.logging and found these entries:

mysql> select distinct message from logging where message like '%savesetting%';
+---------------------------------------------------------------+
| message                                                       |
+---------------------------------------------------------------+
| SaveSettingOnHost('FreqTable') - No database yet              |
| SaveSettingOnHost('ISO639Language0') - No database yet        |
| SaveSettingOnHost('ISO639Language1') - No database yet        |
| SaveSettingOnHost('TVFormat') - No database yet               |
| SaveSettingOnHost('VbiFormat') - No database yet              |
| SaveSettingOnHost('prefDupMethod') - No database yet          |
| SaveSettingOnHost('Country') - No database yet                |
| SaveSettingOnHost('DateFormat') - No database yet             |
| SaveSettingOnHost('EnableMHEG') - No database yet             |
| SaveSettingOnHost('Language') - No database yet               |
| SaveSettingOnHost('MythArchiveVideoFormat') - No database yet |
| SaveSettingOnHost('ShortDateFormat') - No database yet        |
| SaveSettingOnHost('TimeFormat') - No database yet             |
+---------------------------------------------------------------+

I then looked at the timestamp for those messages and looked at my mythbackend logs and found a bunch of these messages a few seconds later:

2012-09-14 18:00:43.237945 E [20573/17377] HttpServer245 mythdbcon.cpp:213 (OpenDatabase) - Unable to connect to database!
2012-09-14 18:00:43.237956 E [20573/17377] HttpServer245 mythdbcon.cpp:214 (OpenDatabase) - Driver error was [1/1040]:
QMYSQL: Unable to connect
Database error was:
Too many connections
2012-09-14 18:00:43.238098 I [20573/17386] HttpServer281 mythdbcon.cpp:808 (prepare) - MySQL server disconnected

So, what seems to have happened here is that mythtv was unable to connect to the database, so it somehow reset those values and they were eventually stored in the database, silently overriding the real configuration. This can be a quite nasty bug, with big unknown consequences.