Fix flaky micrometer retries in javaagent test (#5168)

* Fix flaky micrometer retries in javaagent test

* remove comment

* add clarifying comment

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/internal/AsyncInstrumentRegistry.java

@@ -3,15 +3,13 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-package io.opentelemetry.instrumentation.micrometer.v1_5;
-
-import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.baseUnit;
-import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.description;
+package io.opentelemetry.instrumentation.api.internal;
 
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.api.metrics.Meter;
 import io.opentelemetry.api.metrics.ObservableDoubleMeasurement;
 import io.opentelemetry.api.metrics.ObservableLongMeasurement;
+import io.opentelemetry.instrumentation.api.cache.Cache;
 import java.lang.ref.WeakReference;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -20,15 +18,35 @@ import java.util.function.ToDoubleFunction;
 import java.util.function.ToLongFunction;
 import javax.annotation.Nullable;
 
+// this class must live in the bootstrap classloader - in case different metrics instrumentations
+// (micrometer) get applied to classes in different classloaders, we want them to share the same
+// async instrument registry - because the underlying OTel Meter is shared too. There is only one
+// OTel SDK in the agent, and therefore there must be only one AsyncInstrumentRegistry too -
+// otherwise some async metrics would get lost because of duplicate instrument registrations.
+
 // TODO: refactor this class, there's too much copy-paste here
-final class AsyncInstrumentRegistry {
+public final class AsyncInstrumentRegistry {
+
+  // we need to re-use instrument registries per OpenTelemetry instance so that async instruments
+  // that were created by other OpenTelemetryMeterRegistries can be reused; otherwise the SDK will
+  // start logging errors and async measurements will not be recorded
+  private static final Cache<Meter, AsyncInstrumentRegistry> asyncInstrumentRegistries =
+      Cache.weak();
+
+  /**
+   * Returns the {@link AsyncInstrumentRegistry} for the passed {@link Meter}. There is at most one
+   * {@link AsyncInstrumentRegistry} created for each OpenTelemetry {@link Meter}.
+   */
+  public static AsyncInstrumentRegistry getOrCreate(Meter meter) {
+    return asyncInstrumentRegistries.computeIfAbsent(meter, AsyncInstrumentRegistry::new);
+  }
 
   // using a weak ref so that the AsyncInstrumentRegistry (which is stored in a static maps) does
   // not hold strong references to Meter (and thus make it impossible to collect Meter garbage).
   // in practice this should never return null - OpenTelemetryMeterRegistry maintains a strong
   // reference to both Meter and AsyncInstrumentRegistry; if the meter registry is GC'd then its
   // corresponding AsyncInstrumentRegistry cannot possibly be used; and Meter cannot be GC'd until
-  // OpentelemetryMeterRegistry is GC'd
+  // OpenTelemetryMeterRegistry is GC'd
   private final WeakReference<Meter> meter;
 
   // values from the maps below are never removed - that is because the underlying OpenTelemetry
@@ -47,16 +65,7 @@ final class AsyncInstrumentRegistry {
     this.meter = new WeakReference<>(meter);
   }
 
-  <T> AsyncMeasurementHandle buildGauge(
-      io.micrometer.core.instrument.Meter.Id meterId,
-      Attributes attributes,
-      @Nullable T obj,
-      ToDoubleFunction<T> objMetric) {
-    return buildGauge(
-        meterId.getName(), description(meterId), baseUnit(meterId), attributes, obj, objMetric);
-  }
-
-  <T> AsyncMeasurementHandle buildGauge(
+  public <T> AsyncMeasurementHandle buildGauge(
       String name,
       String description,
       String baseUnit,
@@ -81,16 +90,7 @@ final class AsyncInstrumentRegistry {
     return new AsyncMeasurementHandle(recorder, attributes);
   }
 
-  <T> AsyncMeasurementHandle buildDoubleCounter(
-      io.micrometer.core.instrument.Meter.Id meterId,
-      Attributes attributes,
-      T obj,
-      ToDoubleFunction<T> objMetric) {
-    return buildDoubleCounter(
-        meterId.getName(), description(meterId), baseUnit(meterId), attributes, obj, objMetric);
-  }
-
-  <T> AsyncMeasurementHandle buildDoubleCounter(
+  public <T> AsyncMeasurementHandle buildDoubleCounter(
       String name,
       String description,
       String baseUnit,
@@ -116,7 +116,7 @@ final class AsyncInstrumentRegistry {
     return new AsyncMeasurementHandle(recorder, attributes);
   }
 
-  <T> AsyncMeasurementHandle buildLongCounter(
+  public <T> AsyncMeasurementHandle buildLongCounter(
       String name,
       String description,
       String baseUnit,
@@ -141,7 +141,7 @@ final class AsyncInstrumentRegistry {
     return new AsyncMeasurementHandle(recorder, attributes);
   }
 
-  <T> AsyncMeasurementHandle buildUpDownDoubleCounter(
+  public <T> AsyncMeasurementHandle buildUpDownDoubleCounter(
       String name,
       String description,
       String baseUnit,
@@ -251,7 +251,7 @@ final class AsyncInstrumentRegistry {
     }
   }
 
-  static final class AsyncMeasurementHandle {
+  public static final class AsyncMeasurementHandle {
 
     private final MeasurementsRecorder<?> measurementsRecorder;
     private final Attributes attributes;
@@ -261,7 +261,7 @@ final class AsyncInstrumentRegistry {
       this.attributes = attributes;
     }
 
-    void remove() {
+    public void remove() {
       measurementsRecorder.removeMeasurement(attributes);
     }
   }

instrumentation/micrometer/micrometer-1.5/library/src/main/java/io/opentelemetry/instrumentation/micrometer/v1_5/OpenTelemetryFunctionCounter.java

@@ -5,12 +5,15 @@
 
 package io.opentelemetry.instrumentation.micrometer.v1_5;
 
+import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.baseUnit;
+import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.description;
 import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.tagsAsAttributes;
 
 import io.micrometer.core.instrument.FunctionCounter;
 import io.micrometer.core.instrument.Measurement;
 import io.micrometer.core.instrument.util.MeterEquivalence;
-import io.opentelemetry.instrumentation.micrometer.v1_5.AsyncInstrumentRegistry.AsyncMeasurementHandle;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry.AsyncMeasurementHandle;
 import java.util.Collections;
 import java.util.function.ToDoubleFunction;
 import javax.annotation.Nullable;
@@ -29,7 +32,8 @@ final class OpenTelemetryFunctionCounter<T> implements FunctionCounter, Removabl
     this.id = id;
 
     countMeasurementHandle =
-        asyncInstrumentRegistry.buildDoubleCounter(id, tagsAsAttributes(id), obj, countFunction);
+        asyncInstrumentRegistry.buildDoubleCounter(
+            id.getName(), description(id), baseUnit(id), tagsAsAttributes(id), obj, countFunction);
   }
 
   @Override

instrumentation/micrometer/micrometer-1.5/library/src/main/java/io/opentelemetry/instrumentation/micrometer/v1_5/OpenTelemetryFunctionTimer.java

@@ -15,7 +15,8 @@ import io.micrometer.core.instrument.Statistic;
 import io.micrometer.core.instrument.util.MeterEquivalence;
 import io.micrometer.core.instrument.util.TimeUtils;
 import io.opentelemetry.api.common.Attributes;
-import io.opentelemetry.instrumentation.micrometer.v1_5.AsyncInstrumentRegistry.AsyncMeasurementHandle;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry.AsyncMeasurementHandle;
 import java.util.Collections;
 import java.util.concurrent.TimeUnit;
 import java.util.function.ToDoubleFunction;

instrumentation/micrometer/micrometer-1.5/library/src/main/java/io/opentelemetry/instrumentation/micrometer/v1_5/OpenTelemetryGauge.java

@@ -5,12 +5,15 @@
 
 package io.opentelemetry.instrumentation.micrometer.v1_5;
 
+import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.baseUnit;
+import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.description;
 import static io.opentelemetry.instrumentation.micrometer.v1_5.Bridging.tagsAsAttributes;
 
 import io.micrometer.core.instrument.Gauge;
 import io.micrometer.core.instrument.Measurement;
 import io.micrometer.core.instrument.util.MeterEquivalence;
-import io.opentelemetry.instrumentation.micrometer.v1_5.AsyncInstrumentRegistry.AsyncMeasurementHandle;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry.AsyncMeasurementHandle;
 import java.util.Collections;
 import java.util.function.ToDoubleFunction;
 import javax.annotation.Nullable;
@@ -29,7 +32,8 @@ final class OpenTelemetryGauge<T> implements Gauge, RemovableMeter {
     this.id = id;
 
     gaugeMeasurementHandle =
-        asyncInstrumentRegistry.buildGauge(id, tagsAsAttributes(id), obj, objMetric);
+        asyncInstrumentRegistry.buildGauge(
+            id.getName(), description(id), baseUnit(id), tagsAsAttributes(id), obj, objMetric);
   }
 
   @Override

instrumentation/micrometer/micrometer-1.5/library/src/main/java/io/opentelemetry/instrumentation/micrometer/v1_5/OpenTelemetryMeter.java

@@ -14,7 +14,8 @@ import io.micrometer.core.instrument.Measurement;
 import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.util.MeterEquivalence;
 import io.opentelemetry.api.common.Attributes;
-import io.opentelemetry.instrumentation.micrometer.v1_5.AsyncInstrumentRegistry.AsyncMeasurementHandle;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry.AsyncMeasurementHandle;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;

instrumentation/micrometer/micrometer-1.5/library/src/main/java/io/opentelemetry/instrumentation/micrometer/v1_5/OpenTelemetryMeterRegistry.java

@@ -20,7 +20,7 @@ import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.micrometer.core.instrument.distribution.HistogramGauges;
 import io.micrometer.core.instrument.distribution.pause.PauseDetector;
 import io.opentelemetry.api.OpenTelemetry;
-import io.opentelemetry.instrumentation.api.cache.Cache;
+import io.opentelemetry.instrumentation.api.internal.AsyncInstrumentRegistry;
 import java.util.concurrent.TimeUnit;
 import java.util.function.ToDoubleFunction;
 import java.util.function.ToLongFunction;
@@ -49,20 +49,13 @@ public final class OpenTelemetryMeterRegistry extends MeterRegistry {
     return new OpenTelemetryMeterRegistryBuilder(openTelemetry);
   }
 
-  // we need to re-use instrument registries per OpenTelemetry instance so that async instruments
-  // that were created by other OpenTelemetryMeterRegistries can be reused; otherwise the SDK will
-  // start logging errors and async measurements will not be recorded
-  private static final Cache<io.opentelemetry.api.metrics.Meter, AsyncInstrumentRegistry>
-      asyncInstrumentRegistries = Cache.weak();
-
   private final io.opentelemetry.api.metrics.Meter otelMeter;
   private final AsyncInstrumentRegistry asyncInstrumentRegistry;
 
   OpenTelemetryMeterRegistry(Clock clock, io.opentelemetry.api.metrics.Meter otelMeter) {
     super(clock);
     this.otelMeter = otelMeter;
-    this.asyncInstrumentRegistry =
-        asyncInstrumentRegistries.computeIfAbsent(otelMeter, AsyncInstrumentRegistry::new);
+    this.asyncInstrumentRegistry = AsyncInstrumentRegistry.getOrCreate(otelMeter);
     this.config().onMeterRemoved(OpenTelemetryMeterRegistry::onMeterRemoved);
   }