Prevent unnecessary collect() calls during register()

Author: fstab

prometheus-metrics-core/src/main/java/io/prometheus/metrics/core/metrics/Counter.java

@@ -33,7 +33,7 @@
  * requestCount.withLabelValues("/hello-world", "500").inc();
  * }</pre>
  */
-public class Counter extends StatefulMetric<CounterDataPoint, Counter.DataPoint> implements CounterDataPoint, Collector {
+public class Counter extends StatefulMetric<CounterDataPoint, Counter.DataPoint> implements CounterDataPoint {
 
     private final boolean exemplarsEnabled;
     private final ExemplarSamplerConfig exemplarSamplerConfig;

prometheus-metrics-core/src/main/java/io/prometheus/metrics/core/metrics/MetricWithFixedMetadata.java

@@ -41,6 +41,11 @@ private String makeName(String name, Unit unit) {
         return name;
     }
 
+    @Override
+    public String getPrometheusName() {
+        return metadata.getPrometheusName();
+    }
+
     public static abstract class Builder<B extends Builder<B, M>, M extends MetricWithFixedMetadata> extends Metric.Builder<B, M> {
 
         protected String name;

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/Labels.java

@@ -139,13 +139,24 @@ public static Labels of(String[] names, String[] values) {
      * Dots are treated as underscores, so {@code contains("my.label")} and {@code contains("my_label")} are the same.
      */
     public boolean contains(String labelName) {
+        return get(labelName) != null;
+    }
+
+    /**
+     * Get the label value for a given label name.
+     * <p>
+     * Returns {@code null} if the {@code labelName} is not found.
+     * <p>
+     * Dots are treated as underscores, so {@code get("my.label")} and {@code get("my_label")} are the same.
+     */
+    public String get(String labelName) {
         labelName = prometheusName(labelName);
-        for (String name : prometheusNames) {
-            if (name.equals(labelName)) {
-                return true;
+        for (int i=0; i<prometheusNames.length; i++) {
+            if (prometheusNames[i].equals(labelName)) {
+                return values[i];
             }
         }
-        return false;
+        return null;
     }
 
     private static void sortAndValidate(String[] names, String[] prometheusNames, String[] values) {