node_exporter collector failure for zfs err="couldn't get sysctl: no such file or directory"

[void-fm]

Host operating system: output of uname -a

FreeBSD stable/14-n265566 aarch64 1400500 1400500

node_exporter version: output of node_exporter --version

% node_exporter --version
node_exporter, version (branch: , revision: unknown)
build user:
build date:
go version: go1.20.8
platform: freebsd/arm64
tags: unknown

node_exporter command line flags

(defaults)

node_exporter log output

Nov 15 17:14:22 REDACTED node_exporter[58452]: ts=2023-11-15T17:14:22.737Z caller=collector.go:169 level=error msg="collector failed" name=zfs duration_seconds=0.000465773 err="couldn't get sysctl: no such file or directory"

(every 15 seconds in /var/log/daemon.log)

Workaround for now is editing /usr/local/etc/rc.d/node_exporter and finding this line:

: ${node_exporter_args:=""

and editing it like so:

: ${node_exporter_args:="--no-collector.zfs"}
then restarting node_collector.

[eekay35]

I also found this error after upgrading to FreeBSD 14.0-RELEASE (at least, I hadn't noticed it before that). You shouldn't be editing the RC file, though. Could cause problems in the future and will be overwritten on next node_exporter update. Just add the args line to /etc/rc.conf and restart the node_exporter service:

sysrc node_exporter_args="--no-collector.zfs"
service node_exporter restart

[dekimsey]

I pulled the list of mibs being scanned and passed them to sysctl on my FreeBSD 14.0 box, looks like kstat.zfs.misc.arcstats.p is the missing oid. The code suggests this is known, but it doesn't stop trying to access the value so at least the error is simply noisy, the rest of the zfs stats are being collected normally.

Additionally, I spiked a quick change that would use getUname to grab the OS Release and then add the appropriate sysctl stats. It's not clear to me if that is a road the project would want to go. I'd be more comfortable proposing it if I had more samples from the other *BSDs to allow a major minor function to return something sensible, but I don't have any.

[eekay35]

Excellent, thank you! Once this new code goes into place via FBSD's ports/packages, I'll give it a try and verify. Looks good, though. I (and likely many others) appreciate it!