Update _handleStaticLabels

lib/metrics/prometheus.js

@@ -34,13 +34,15 @@ class PrometheusMetric {
     }
 
     _handleStaticLabels(labels) {
+        const updatedLabels = [...labels];
         if (this.staticLabels !== undefined) {
             Object.keys(this.staticLabels).forEach((name) => {
-                if (labels.indexOf(this.staticLabels[name]) === -1) {
-                    labels.unshift(this.staticLabels[name]);
+                if (updatedLabels.indexOf(this.staticLabels[name]) === -1) {
+                    updatedLabels.unshift(this.staticLabels[name]);
                 }
             });
         }
+        return updatedLabels;
     }
 
     _normalize(str) {
@@ -50,30 +52,22 @@ class PrometheusMetric {
     }
 
     increment(amount, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.metric.labels.apply(this.metric, updatedLabels).inc(amount);
     }
 
     decrement(amount, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.metric.labels.apply(this.metric, updatedLabels).dec(amount);
     }
 
     observe(value, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.metric.labels.apply(this.metric, updatedLabels).observe(value);
     }
 
     gauge(amount, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         if (amount < 0) {
             this.metric.labels.apply(this.metric, updatedLabels).dec(Math.abs(amount));
         } else {
@@ -82,23 +76,17 @@ class PrometheusMetric {
     }
 
     set(value, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.metric.labels.apply(this.metric, updatedLabels).set(value);
     }
 
     timing(value, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.observe(value, updatedLabels);
     }
 
     endTiming(startTime, labels) {
-        let updatedLabels = [...labels];
-        this._handleStaticLabels(updatedLabels);
-        updatedLabels = updatedLabels.map(this._normalize);
+        const updatedLabels = this._handleStaticLabels(labels).map(this._normalize);
         this.timing(Date.now() - startTime, updatedLabels);
     }
 }