[ovirt-devel] [VDSM] dynamic tuning of logging

[Francesco Romani]

Hi everyone,

I'd like to allow VDSM to change the verbosity of its loggers at runtime,
without restarting the daemon.

Doing so, we could make the default silent, and we'll also offer a convenient
way for users to enable/disable debug log. When something has to be debugged
or better understood, one can temporarily increase verbosiness, and then restore
the normal level, with minimal service disruption (= no vdsmd restart).

Currently vdsm uses the standard 'logging' module, which, to best of my knowledge,
allows to tune levels at runtime since forever.

So, the main concern is the interface. I see these options, from the one I like
the most to the one I like the least:

1. add a inotify helper/trigger, just reload the config file when changed.
   Seems safe and convenient, but will lead to a "complex" patch.

2. just add a new verb to be used by Engine/vdsClient/whatever.
   Tuning log levels is not more dangerous than a truckload of verbs we already
   expose

3. build on the manhole integration (https://gerrit.ovirt.org/#/c/32147/).

4. use signals (SIGUSR? SIGHUP?)

Thoughts welcome

-- 
Francesco Romani
RedHat Engineering Virtualization R & D
Phone: 8261328
IRC: fromani