Added detailed filtering capabilities for systemd_units

plugins/systemd/systemd_units

@@ -13,21 +13,38 @@ Linux systems with systemd installed.
 
 =head1 CONFIGURATION
 
-None needed. You may optionally pass warning and critical values for any of the possible states (active,
+No configuration is required for this plugin. You may optionally pass warning and critical values for any
-reloading, inactive, failed, activating, deactivating) like so:
+of the possible states (active, reloading, inactive, failed, activating, deactivating), and you may
+additionally pass both global and state-specific include/exclude filters to include only units you care
+about and/or exclude units you don't care about.
+
+(Note that for failed units, default warning and critical values are set to 0 and 10, respectively. No other
+states have default levels set.)
+
+Value calculations for each state are made using the following algorithm (all filters performed using \`egrep\`):
+
+1. Global include rules are applied on the output of \`systemctl list-units --all --no-legend\`;
+2. Global exclude rules are then applied to the result of that;
+3. Then, for each state, this global output is further filtered by include, then exclude rules for the state;
+4. Then the result is filtered for the given state and the remaining units counted and listed.
+
+An example configuration might be something like this:
 
  [systemd_units]
-     env.failed_warning 0
+ env.failed_warning 0
-     env.failed_critical 5
+ env.failed_critical 5
-     env.inactive_warning 10
+ env.inactive_warning 10
-     env.inactive_critical 20
+ env.inactive_critical 20
-     
+ env.exclude boring
-Note that for failed units, default warning and critical values are set to 0 and 10, respectively. No other
+ env.inactive_exclude sleepy
-states have default levels set.
+
+In the example above, we've overridden the default warning and critical levels for failed units, added warning
+and critical levels for inactive units, then filtered out boring units from all results and filtered out sleepy
+units from results for the inactive state.
 
 =head1 AUTHOR
 
-Olivier Mehani <shtrom+munin@ssji.net>
+Olivier Mehani <shtrom+munin@ssji.net> with contributions from Kael Shipman <kael.shipman@gmail.com>
 
 =head1 LICENSE
 
@@ -51,6 +68,10 @@ states="active \
 	failed \
 	activating \
 	deactivating"
+
+include="${include:-.*}"
+exclude="${exclude:-^$}"
+
 autoconf() {
 	which systemctl >/dev/null && \
 	       systemctl  --state=failed --no-pager --no-legend	>/dev/null 2>&1 && echo yes || echo "no (No systemctl or error running it)"
@@ -73,11 +94,29 @@ EOF
 }
 
 fetch () {
-	tmp=$(systemctl --no-pager --no-legend --all | awk '{print $1, $3}')
+    # Get all units, filtering by global include/exclude rules
+    local state_include state_exclude state_tmp tmp
+	tmp=$(systemctl --no-pager --no-legend --all | egrep "$include" | egrep -v "$exclude" | awk '{print $1, $3}')
+
+    # For each state, echo the number of units and some extra info, filtering for state-specific include/excludes
 	for state in $states ; do
-		count=$(echo "$tmp" | grep -c "$state$")
+        # Get state-specific include/excludes, if present
+        state_include="$(eval echo "\$${state}_include")"
+        state_exclude="$(eval echo "\$${state}_exclude")"
+        state_tmp="$tmp"
+
+        # Filter
+        if [ -n "$state_include" ]; then
+            state_tmp="$(echo "$state_tmp" | egrep "$state_include")"
+        fi
+        if [ -n "$state_exclude" ]; then
+            state_tmp="$(echo "$state_tmp" | egrep -v "$state_exclude")"
+        fi
+
+        # Count and output
+		count=$(echo "$state_tmp" | grep -c "$state$")
 		echo "$state.value $count"
-		extinfo=$(echo "$tmp" | grep "$state$" | cut -d " " -f 1 | tr '\n' ' ')
+		extinfo=$(echo "$state_tmp" | grep "$state$" | cut -d " " -f 1 | tr '\n' ' ')
 		if [ -n "$extinfo" ]; then
 			echo "$state.extinfo" "$extinfo"
 		fi