Filter out uninstalled systemd units when collecting all units (#1011)

fixes #567

Signed-off-by: Matthew McGinn <mamcgi@gmail.com>

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 **Breaking changes**
 
-* [CHANGE]
+* [CHANGE] Filter out non-installed units when collecting all systemd units #1011
 * [FEATURE] Collect NRefused property for systemd socket units (available as of systemd v239)
 * [FEATURE] Collect NRestarts property for systemd service units
 * [FEATURE] Add socket unit stats to systemd collector #968

collector/systemd_linux.go

@@ -227,7 +227,9 @@ func (c *systemdCollector) getAllUnits() ([]unit, error) {
 	}
 	defer conn.Close()
 
-	allUnits, err := conn.ListUnits()
+	// Filter out any units that are not installed and are pulled in only as dependencies.
+	allUnits, err := conn.ListUnitsFiltered([]string{"loaded"})
+
 	if err != nil {
 		return nil, err
 	}