Delegate to ConcurrentHashMap values Spliterator in AbstractRegistry (#…

…988)

Override AbstractRegistry::spliterator to return the ConcurrentHashMap's
values Spliterator, which has estimated size and other characteristics set.

spectator-api/src/main/java/com/netflix/spectator/api/AbstractRegistry.java

@@ -24,6 +24,7 @@
 
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.function.Function;
@@ -278,6 +279,11 @@ protected <T extends Meter> T getOrCreate(Id id, Class<T> cls, T dflt, Function<
     return meters.values().iterator();
   }
 
+  @Override
+  public final Spliterator<Meter> spliterator() {
+    return meters.values().spliterator();
+  }
+
   /**
    * Can be called by sub-classes to remove expired meters from the internal map.
    * The SwapMeter types that are returned will lookup a new copy on the next access.

spectator-api/src/test/java/com/netflix/spectator/api/RegistryTest.java

@@ -27,6 +27,7 @@
 import java.util.List;
 import java.util.LongSummaryStatistics;
 import java.util.Map;
+import java.util.Spliterator;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.TimeUnit;
@@ -585,6 +586,20 @@ public void maxGaugeCanBeNegative() {
     Assertions.assertEquals(-42.0, r.maxGauge("test").value(), 1e-12);
   }
 
+  @Test
+  public void spliteratorCharacteristicsAndEstimatedSize() {
+    Registry registry = newRegistry(false, 20);
+    registry.counter("foo").increment();
+    registry.counter("bar").increment();
+    registry.counter("baz").increment();
+
+    Spliterator<Meter> spliterator = registry.spliterator();
+
+    Assertions.assertTrue(spliterator.hasCharacteristics(Spliterator.NONNULL));
+    Assertions.assertTrue(spliterator.hasCharacteristics(Spliterator.CONCURRENT));
+    Assertions.assertEquals(3, spliterator.estimateSize());
+  }
+
   @Test
   public void customIdTags() {
     DefaultRegistry r = newRegistry(false, 10000);