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 )