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nixos/munin: fix broken plugin wrappers

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The munin-node service used wrapProgram to inject environment variables.
This doesn't work because munin plugins depend on argv[0], which is
overwritten when the executable is a script with a shebang line (example
below).

This commit removes the wrappers and instead passes the required
environment variables to munin-node.

Eliminating the wrappers resulted in some broken plugins, e.g., meminfo
and hddtemp_smartctl. That was fixed with the per-plugin configuration.

Example:

  The plugin if_eth0 is a symlink to /.../plugins/if_, which uses $0
  to determine that it should monitor traffic on the eth0 interface.

  if_ is a wrapped program, and runs `exec -a "$0" .if_-wrapped`

  .if_-wrapped has a "#!/nix/.../bash" line, which results in bash
  changing $0, and as a result the plugin thinks my interface
  is called "-wrapped".
This commit is contained in:
Kjetil Orbekk 2017-11-21 12:40:40 -05:00 committed by Bjørn Forsman
parent a2dc37c7d1
commit bd3e49a80e
1 changed files with 31 additions and 37 deletions
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68
nixos/modules/services/monitoring/munin.nix
View file

@ -17,40 +17,6 @@ let
nodeCfg = config.services.munin-node;
cronCfg = config.services.munin-cron;
muninPlugins = pkgs.stdenv.mkDerivation {
name = "munin-available-plugins";
buildCommand = ''
mkdir -p $out
cp --preserve=mode ${pkgs.munin}/lib/plugins/* $out/
for file in $out/*; do
case "$file" in
*/plugin.sh|*/plugins.history)
chmod +x "$file"
continue;;
esac
# read magic makers from the file
family=$(sed -nr 's/.*#%#\s+family\s*=\s*(\S+)\s*/\1/p' $file)
cap=$(sed -nr 's/.*#%#\s+capabilities\s*=\s*(.+)/\1/p' $file)
wrapProgram $file \
--set PATH "/run/wrappers/bin:/run/current-system/sw/bin" \
--set MUNIN_LIBDIR "${pkgs.munin}/lib" \
--set MUNIN_PLUGSTATE "/var/run/munin"
# munin uses markers to tell munin-node-configure what a plugin can do
echo "#%# family=$family" >> $file
echo "#%# capabilities=$cap" >> $file
done
# NOTE: we disable disktstats because plugin seems to fail and it hangs html generation (100% CPU + memory leak)
rm -f $out/diskstats
'';
buildInputs = [ pkgs.makeWrapper ];
};
muninConf = pkgs.writeText "munin.conf"
''
dbdir /var/lib/munin
@ -83,6 +49,29 @@ let
${nodeCfg.extraConfig}
'';
pluginConf = pkgs.writeText "munin-plugin-conf"
''
[hddtemp_smartctl]
user root
group root
[meminfo]
user root
group root
[ipmi*]
user root
group root
'';
pluginConfDir = pkgs.stdenv.mkDerivation {
name = "munin-plugin-conf.d";
buildCommand = ''
mkdir $out
ln -s ${pluginConf} $out/nixos-config
'';
};
in
{
@ -179,17 +168,22 @@ in
description = "Munin Node";
after = [ "network.target" ];
wantedBy = [ "multi-user.target" ];
path = [ pkgs.munin ];
path = with pkgs; [ munin smartmontools "/run/current-system/sw" "/run/wrappers" ];
environment.MUNIN_LIBDIR = "${pkgs.munin}/lib";
environment.MUNIN_PLUGSTATE = "/var/run/munin";
environment.MUNIN_LOGDIR = "/var/log/munin";
preStart = ''
echo "updating munin plugins..."
mkdir -p /etc/munin/plugins
rm -rf /etc/munin/plugins/*
PATH="/run/wrappers/bin:/run/current-system/sw/bin" ${pkgs.munin}/sbin/munin-node-configure --shell --families contrib,auto,manual --config ${nodeConf} --libdir=${muninPlugins} --servicedir=/etc/munin/plugins 2>/dev/null | ${pkgs.bash}/bin/bash
${pkgs.munin}/bin/munin-node-configure --suggest --shell --families contrib,auto,manual --config ${nodeConf} --libdir=${pkgs.munin}/lib/plugins --servicedir=/etc/munin/plugins --sconfdir=${pluginConfDir} 2>/dev/null | ${pkgs.bash}/bin/bash
# NOTE: we disable disktstats because plugin seems to fail and it hangs html generation (100% CPU + memory leak)
rm /etc/munin/plugins/diskstats || true
'';
serviceConfig = {
ExecStart = "${pkgs.munin}/sbin/munin-node --config ${nodeConf} --servicedir /etc/munin/plugins/";
ExecStart = "${pkgs.munin}/sbin/munin-node --config ${nodeConf} --servicedir /etc/munin/plugins/ --sconfdir=${pluginConfDir}";
};
};