Ignore noop children in CompositeMeter

jkemming · Jan 28, 2024 · 5cb55eb · 5cb55eb
1 parent b9b2f0d
commit 5cb55eb
Showing 1 changed file with 25 additions and 10 deletions.
diff --git a/...er-core/src/main/java/io/micrometer/core/instrument/composite/AbstractCompositeMeter.java b/...er-core/src/main/java/io/micrometer/core/instrument/composite/AbstractCompositeMeter.java
@@ -19,18 +19,18 @@
 import io.micrometer.core.instrument.AbstractMeter;
 import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.noop.NoopMeter;
 
 import java.util.Collections;
 import java.util.IdentityHashMap;
-import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 abstract class AbstractCompositeMeter<T extends Meter> extends AbstractMeter implements CompositeMeter {
 
     private final AtomicBoolean childrenGuard = new AtomicBoolean();
 
-    private Map<MeterRegistry, T> children = Collections.emptyMap();
+    private State state = new State(Collections.emptyMap());
 
     @Nullable
     private volatile T noopMeter;
@@ -45,13 +45,12 @@ abstract class AbstractCompositeMeter<T extends Meter> extends AbstractMeter imp
     abstract T registerNewMeter(MeterRegistry registry);
 
     final Iterable<T> getChildren() {
-        return children.values();
+        return state.children.values();
     }
 
     T firstChild() {
-        final Iterator<T> i = children.values().iterator();
-        if (i.hasNext())
-            return i.next();
+        if (state.firstNonNoopChild != null)
+            return state.firstNonNoopChild;
 
         // There are no child meters. Return a lazily instantiated no-op meter.
         final T noopMeter = this.noopMeter;
@@ -73,9 +72,9 @@ public final void add(MeterRegistry registry) {
         for (;;) {
             if (childrenGuard.compareAndSet(false, true)) {
                 try {
-                    Map<MeterRegistry, T> newChildren = new IdentityHashMap<>(children);
+                    Map<MeterRegistry, T> newChildren = new IdentityHashMap<>(state.children);
                     newChildren.put(registry, newMeter);
-                    this.children = newChildren;
+                    this.state = new State(newChildren);
                     break;
                 }
                 finally {
@@ -95,9 +94,9 @@ public final void remove(MeterRegistry registry) {
         for (;;) {
             if (childrenGuard.compareAndSet(false, true)) {
                 try {
-                    Map<MeterRegistry, T> newChildren = new IdentityHashMap<>(children);
+                    Map<MeterRegistry, T> newChildren = new IdentityHashMap<>(state.children);
                     newChildren.remove(registry);
-                    this.children = newChildren;
+                    this.state = new State(newChildren);
                     break;
                 }
                 finally {
@@ -107,4 +106,20 @@ public final void remove(MeterRegistry registry) {
         }
     }
 
+    private class State {
+
+        private final Map<MeterRegistry, T> children;
+
+        @Nullable
+        private final T firstNonNoopChild;
+
+        State(final Map<MeterRegistry, T> children) {
+            this.children = children;
+            firstNonNoopChild = children.values()
+                .stream()
+                .filter(child -> !(child instanceof NoopMeter))
+                .findFirst()
+                .orElse(null);
+        }
+    }
 }