start on code review updates

Signed-off-by: Jay DeLuca <[email protected]>

Author: jaydeluca

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/registry/Collector.java

@@ -94,7 +94,5 @@ default String getPrometheusName() {
    * @return the metric type, or {@code null} if unknown
    */
   @Nullable
-  default MetricType getMetricType() {
-    return null;
-  }
+  MetricType getMetricType();
 }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/registry/MetricType.java

@@ -1,30 +1,23 @@
 package io.prometheus.metrics.model.registry;
 
 /**
- * Represents the type of a Prometheus metric.
+ * Represents the type of Prometheus metric.
  *
  * <p>This enum is used for early validation when registering collectors with duplicate Prometheus
  * names. All collectors with the same Prometheus name must have the same metric type.
  */
 public enum MetricType {
-  /** Counter metric type - monotonically increasing value. */
   COUNTER,
 
-  /** Gauge metric type - value that can go up or down. */
   GAUGE,
 
-  /** Histogram metric type - samples observations and counts them in buckets. */
   HISTOGRAM,
 
-  /** Summary metric type - samples observations and calculates quantiles. */
   SUMMARY,
 
-  /** Info metric type - key-value pairs providing information about the entity. */
   INFO,
 
-  /** StateSet metric type - represents a set of boolean states. */
   STATESET,
 
-  /** Unknown metric type - for custom or legacy collectors. */
   UNKNOWN
 }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/registry/MultiCollector.java

@@ -8,7 +8,6 @@
 import javax.annotation.Nullable;
 
 /** Like {@link Collector}, but collecting multiple Snapshots at once. */
-@FunctionalInterface
 public interface MultiCollector {
 
   /** Called when the Prometheus server scrapes metrics. */
@@ -86,7 +85,5 @@ default List<String> getPrometheusNames() {
    * @return the metric type, or {@code null} if unknown
    */
   @Nullable
-  default MetricType getMetricType(String prometheusName) {
-    return null;
-  }
+  MetricType getMetricType(String prometheusName);
 }

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/registry/PrometheusRegistry.java

@@ -6,6 +6,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 
 public class PrometheusRegistry {
@@ -26,6 +27,7 @@ public void register(Collector collector) {
   public void register(MultiCollector collector) {
     validateTypeConsistency(collector);
     multiCollectors.add(collector);
+    cacheMetricIdentifier(collector);
   }
 
   /**
@@ -108,6 +110,19 @@ private void cacheMetricIdentifier(Collector collector) {
     }
   }
 
+  /**
+   * Caches the metric identifier for lookup during future registrations.
+   */
+  private void cacheMetricIdentifier(MultiCollector collector) {
+    for (String name : collector.getPrometheusNames()) {
+      MetricType type = collector.getMetricType(name);
+
+      if (name != null) {
+        registeredMetrics.putIfAbsent(name, new MetricIdentifier(name, type));
+      }
+    }
+  }
+
   public void unregister(Collector collector) {
     collectors.remove(collector);
     // Note: We don't remove from cache because another collector with the same name might exist