Fix munin_stats plugin when running munin-node only #30426

florianjacob · 2017-10-14T21:07:48Z

Motivation for this change

If you run munin-node without having munin-cron on the same machine, the automatically enabled munin_stats plugin which prints general statistics fails on every munin call (i.e. every 5 minutes):

munin-node: Error output from munin_stats:
munin-node: Error in tempfile() using template /var/run/munin/XXXXXXXXXX: Parent directory (/var/run/munin/) does not exist at /nix/store/dr4inq7f91d62mbr7qphhmxf8320i44r-munin-2.0.33/lib/perl5/site_perl/Munin/Plugin.pm line 280.
munin-node: Service 'munin_stats' exited with status 2/0.

Happens on 17.09 and master. This is because munin-node does not create the MUNIN_PLUGSTATE directory /var/run/munin. This is fixed with 95bb82d by using systemd.tmpfiles, would be nice to get this cherry-picked to 17.09. 086c0e6 converts munin-cron to systemd.tmpfiles as well, but that commit is not necessary to fix this issue (and not strictly necessary at all, of course. Is there a policy regarding mkdir+chown activationScripts vs. systemd.tmpfiles?)

Things done

Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
Built on platform(s)
- NixOS
- macOS
- other Linux distributions
Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
Tested execution of all binary files (usually in ./result/bin/)
Fits CONTRIBUTING.md.

to match with munin-node.

bjornfor · 2017-10-15T09:40:30Z

Is there a policy regarding mkdir+chown activationScripts vs. systemd.tmpfiles?

Not that I know of.

bjornfor · 2017-10-15T13:30:58Z

nixos/modules/services/monitoring/munin.nix

@@ -193,6 +193,9 @@ in
      };
    };

+    # munin_stats plugin breaks as of 2.0.33 when this doesn't exist
+    systemd.tmpfiles.rules = [ "d /var/run/munin 0755 munin munin -" ];


Perhaps "serviceConfig.RuntimeDirectory=munin" is more appropriate here?

I was totally not aware of those serviceConfig options, they look great, thank you! 😃

Problem here would be though that /var/run/munin is not only used as your usual pid file folder, but also the plugin state is redirected from the default location of /var/lib/munin/plugin-state to /var/run/munin via the MUNIN_PLUGSTATE variable – the latter causing the actual problem with munin_stats plugin. It might not be good to clear the plugin state on every restart of the service. But I don't know why that's actually done.

The dual use traces back to the first commit of the service, @domenkozar, do you still know your reasons why you set MUNIN_PLUGSTATE to /var/run/munin?

florianjacob added 2 commits October 14, 2017 02:39

nixos/munin: Create MUNIN_PLUGSTATE dir to fix munin_stats plugin

95bb82d

nixos/munin: move munin-cron to systemd.tmpfiles

086c0e6

to match with munin-node.

bjornfor reviewed Oct 15, 2017

View reviewed changes

domenkozar merged commit 43f94ff into NixOS:master Oct 21, 2017

florianjacob deleted the fix-munin_stats-plugin branch October 22, 2017 19:45

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Fix munin_stats plugin when running munin-node only #30426

Fix munin_stats plugin when running munin-node only #30426

florianjacob commented Oct 14, 2017

bjornfor commented Oct 15, 2017

bjornfor Oct 15, 2017

Mic92 Oct 15, 2017

florianjacob Oct 16, 2017

Fix munin_stats plugin when running munin-node only #30426

Fix munin_stats plugin when running munin-node only #30426

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florianjacob commented Oct 14, 2017

Motivation for this change

Things done

bjornfor commented Oct 15, 2017

bjornfor Oct 15, 2017

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Mic92 Oct 15, 2017

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florianjacob Oct 16, 2017

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