Re: Monitoring Btrfs

[Kyle Manna <2bluesc@gmail.com>]

On Mon, Oct 17, 2016 at 9:44 AM, Stefan Malte Schumacher
<stefan.m.schumacher@gmail.com> wrote:
> Hello
>
> I would like to monitor my btrfs-filesystem for missing drives. On
> Debian mdadm uses a script in /etc/cron.daily, which calls mdadm and
> sends an email if anything is wrong with the array. I would like to do
> the same with btrfs. In my first attempt I grepped and cut the
> information from "btrfs fi show" and let the script send an email if
> the number of devices was not equal to the preselected number.
>
> ...
>
> 1) Has anybody already written a script like this? After all, there is
> no need to reinvent the wheel a second time.

Not that I have a solution to your primary question regarding message
parsing, but do something different which may offer a different
perspective on your monitoring and reporting.

I employ systemd with timers to scrub my btrfs volumes[0][1] every
week.  I used to use either an OnFailure[2] trigger or my failure
monitor log (aka systemd-journal) parser[3] to send me emails if the
service failed to run.  This is a more "modern" approach to
cron.weekly + custom shell script for people that like systemd, love
it or hate it.

Recently I dropped the systemd journal parser for remote logging with
rsyslog + Papertrail[4] with a few alerts for things like "systemd
Failed to start" which indicates that the script returned a non-zero
exit code.  Papertrail then emails me when any of a handful of
machines trip up.

It's also worth noting logstash[5] (or similar) may be another way to
parse log files.  It could be a bloated overkill solution for
something that a 10 line shell script could accomplish, depends on if
you leverage it for things beyond basic log parsing.

[0] https://github.com/kylemanna/systemd-utils/blob/master/units/btrfs-scrub.service
[1] https://github.com/kylemanna/systemd-utils/blob/master/units/btrfs-scrub.timer
[2] https://github.com/kylemanna/systemd-utils/tree/master/onfailure
[3] https://github.com/kylemanna/systemd-utils/tree/master/failure-monitor
[4] https://blog.kylemanna.com/linux/logging-all-the-things-with-rsyslog-and-papertrail/
[5] https://www.elastic.co/guide/en/logstash/current/introduction.html