Re: [libvirt] [PATCH] logging: remove concept of default log priority

On Tue, May 31, 2016 at 10:52:35AM +0200, Erik Skultety wrote: > On 11/05/16 16:12, Daniel P. Berrange wrote: >> The logging framework has categories which can be selectively >> enabled/disabled by setting a suitable LIBVIRT_LOG_FILTERS >> environment variable or config file setting. >> >> Along side that we also have the LIBVIRT_DEBUG environment >> variable which unconditionally enables every single category >> at DEBUG level. With the amount of logging produced by libvirt >> these days, the signal/noise ratio in the output from setting >> LIBVIRT_DEBUG is to poor for it to be useful. >> >> Originally the LIBVIRT_DEBUG env variable had a very specific >> use case - it resulted in logging of anything in our public >> API entrypoints. eg it turned on src/libvirt.c debugging and >> nothing else. Additionally it would always result in log >> messages being sent to stderr. >> >> When applied to any of the daemons, the log output no longers >> gets sent to stderr, but rather to whatever default log output >> has been configured by the daemon. If no log_outputs setting >> or LIBVIRT_LOG_OUTPUTS env is set, then messages will often >> go to the systemd journal or a /var/log/libvirt/libvirtd.log >> file rather than stderr. >> >> These factors have conspired to make the LIBVIRT_DEBUG env >> and/or default log priority to be pretty useless in the real >> world. >> >> This change attempts to take us back towards the original >> semantics of the LIBVIRT_DEBUG env variable as follows. >> >> If LIBVIRT_DEBUG is set to a plain integer, or log level >> string, then it will turn on logging for the "libvirt" log >> category at that level. Any other string will be parsed in >> the same way as LIBVIRT_LOG_FILTERS would be. In all cases >> use of LIBVIRT_DEBUG will result in an explicit output being >> added for stderr. This ensures that messages always go to >> stderr, even if other outputs are already configured. >> >> IOW, LIBVIRT_DEBUG=1 virsh or LIBVIRT_DEBUG=1 libvirtd >> will both result in printing logs of libvirt public API >> calls to stderr. Meanwhile setting LIBVIRT_DEBUG="1:qemu" >> is equivalent to setting LIBVIRT_LOG_FILTERS="1:qemu" and >> LIBVIRT_LOG_OUTPUTS="1:stderr" >> >> Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; FYI, I'm still thinking about how to proceed with this patch given the feedback so far....so consider this "on hold" until I come up with a better idea. In the meantime we must not make the problem worse. ie we should *not* expose the default logging level config via the admin API. Only expose log filters + outputs. Regards, Daniel