Log a warning if ups.status is not in the variables requested to be e…

…xported

README.md

@@ -91,7 +91,7 @@ Therefore, these are all enabled in the default value for `--nut.statuses`.
 The exporter allows for per-scrape overrides of command line parameters by passing query string parameters. This enables a single nut_exporter to scrape multiple NUT servers
 
 The following query string parameters can be passed to the `/ups_metrics` path:
-  * `ups` - Required if more than one UPS is present in NUT)
+  * `ups` - Required if more than one UPS is present in NUT
   * `server` - Overrides the command line parameter `--nut.server`
   * `username` - Overrides the command line parameter `--nut.username`
   * `password` - Overrides the environment variable NUT_EXPORTER_PASSWORD. It is **strongly** recommended to avoid passing credentials over http unless the exporter is configured with TLS

nut_exporter.go

@@ -162,13 +162,23 @@ func main() {
 	}
 
 	variables := []string{}
+	hasUpsStatusVariable := false
 	for _, varName := range strings.Split(*enableFilter, ",") {
 		// Be nice and clear spaces for those that like them
 		variable := strings.Trim(varName, " ")
 		if variable == "" {
 			continue
 		}
-		variables = append(variables, strings.Trim(varName, " "))
+		variables = append(variables, variable)
+
+		// Special handling because this is an important and commonly needed variable
+		if variable == "ups.status" {
+			hasUpsStatusVariable = true
+		}
+	}
+
+	if !hasUpsStatusVariable {
+		level.Warn(logger).Log("msg", "Exporter has been started without `ups.status` variable to be exported with --nut.vars_enable. Online/offline/etc statuses will not be reported!")
 	}
 
 	statuses := []string{}