Thu Dec 20 22:28:31 CET 2007

don't trust mysql5 wait_timeout-value

brrfft, it took some time to find this one.. I had some unexpected errors on two mysql servers running as multiple masters. after inspecting the mysql settings it showed something like this:

mysql> show variables;
[..]
| version_compile_os              | pc-linux-gnu                | 
| wait_timeout                    | 28800                       | 
+---------------------------------+-----------------------------+

my initial suspicion that a timeout occured due the wait_timeout setting was thus dropped, as the default setting of eight hours (28800 seconds) were not suspicious at all.
so i had to focus on other reasons for mysql's misbehaviour. after some exploration from within the mysql client i took a look at the config-file (/etc/mysql/my.cnf in debian et al) and i stumbled upon this:
the setting for wait_timeout in there was surprisingly low. but this value - which was obviously used by the server, as it caused my problems - was not used when displaying the global variables via show variables. incredible. all other variables seem to be displayed correctly.
anyhow, it seems one should not trust the varialbe-values from within mysql client.
( tested with 5.0.32 and 5.0.45 )


Posted by iso | Permanent Link | Tags: mysql, annoyance, ubuntu, linux | comments >>