psu plugin is not compatible with BusyBox pgrep

[cl-parsons]

OS: Alpine Linux 3.14 Munin version : 2.0.67

The "-u" option does not exist in BusyBox version of pgrep.

$ munin-run psu_mailman
pgrep: unrecognized option: U

[sumpfralle]

Busybox is a tricky reference :)

Here on my Debian system, there is no pgrep applet enabled in busybox. On an OpenWrt system, busybox contains pgrep, but supports neither -u nor -U (both are used by the plugin).

This specific plugin boils down to a single line:

(pgrep -u "$name"; pgrep -U "$name") | sort -u | wc -l

I see the following options:

• A) We could add 2>/dev/null to the second pgrep call in order to silence the error message. But this would degrade the plugins's functionality in a subtile way on some systems.
• B) We could check, whether the available pgrep implementation supports -U and abort, if it lacks the feature.
• C) We could find a different approach for listing the processes based on their effective or real user ID.

I would tend to rule out (C), since a major feature of this specific plugin seems to be its simplicity. (A) feels undesirable to me, since it can be surprising. Thus we are left with (B), I guess.

Or any other ideas?

[sertonix]

Alpine now patches busybox pgrep to add the -u and -U options.

[steveschnepp]

I would tend to favor some sane default, plus a config time change for others via the usual env variables mechanism.