Closing a kafka producer/consumer should not disable metrics from other consumers/producers (#11975)

instrumentation/kafka/kafka-clients/kafka-clients-0.11/testing/src/main/java/io/opentelemetry/instrumentation/kafka/internal/AbstractOpenTelemetryMetricsReporterTest.java

@@ -32,6 +32,7 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Random;
 import java.util.Set;
+import java.util.concurrent.CopyOnWriteArrayList;
 import org.apache.kafka.clients.CommonClientConfigs;
 import org.apache.kafka.clients.consumer.ConsumerConfig;
 import org.apache.kafka.clients.consumer.KafkaConsumer;
@@ -70,6 +71,13 @@ public abstract class AbstractOpenTelemetryMetricsReporterTest {
   private static KafkaProducer<byte[], byte[]> producer;
   private static KafkaConsumer<byte[], byte[]> consumer;
 
+  private static final List<OpenTelemetryMetricsReporter> metricsReporters =
+      new CopyOnWriteArrayList<>();
+
+  static {
+    OpenTelemetryMetricsReporter.setListener(metricsReporters::add);
+  }
+
   @BeforeEach
   void beforeAll() {
     // only start the kafka container the first time this runs
@@ -90,14 +98,16 @@ public abstract class AbstractOpenTelemetryMetricsReporterTest {
 
   @AfterAll
   static void afterAll() {
-    kafka.stop();
     producer.close();
     consumer.close();
+    kafka.stop();
   }
 
   @AfterEach
   void tearDown() {
-    OpenTelemetryMetricsReporter.resetForTest();
+    for (OpenTelemetryMetricsReporter metricsReporter : metricsReporters) {
+      metricsReporter.resetForTest();
+    }
   }
 
   protected abstract InstrumentationExtension testing();
@@ -186,6 +196,14 @@ public abstract class AbstractOpenTelemetryMetricsReporterTest {
 
   @Test
   void observeMetrics() {
+    // Firstly create new producer and consumer and close them. This is done tp verify that metrics
+    // are still produced after closing one producer/consumer. See
+    // https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/11880
+    KafkaProducer<byte[], byte[]> producer2 = new KafkaProducer<>(producerConfig());
+    KafkaConsumer<byte[], byte[]> consumer2 = new KafkaConsumer<>(consumerConfig());
+    producer2.close();
+    consumer2.close();
+
     produceRecords();
     consumeRecords();
 
@@ -405,7 +423,9 @@ public abstract class AbstractOpenTelemetryMetricsReporterTest {
     Map<String, List<KafkaMetricId>> kafkaMetricsByGroup =
         TestMetricsReporter.seenMetrics.stream().collect(groupingBy(KafkaMetricId::getGroup));
     List<RegisteredObservable> registeredObservables =
-        OpenTelemetryMetricsReporter.getRegisteredObservables();
+        metricsReporters.stream()
+            .flatMap(metricsReporter -> metricsReporter.getRegisteredObservables().stream())
+            .collect(toList());
     // Iterate through groups in alpha order
     for (String group : kafkaMetricsByGroup.keySet().stream().sorted().collect(toList())) {
       List<KafkaMetricId> kafkaMetricIds =

instrumentation/kafka/kafka-clients/kafka-clients-common/library/src/main/java/io/opentelemetry/instrumentation/kafka/internal/OpenTelemetryMetricsReporter.java

@@ -41,28 +41,35 @@ public final class OpenTelemetryMetricsReporter implements MetricsReporter {
 
   private static final Logger logger =
       Logger.getLogger(OpenTelemetryMetricsReporter.class.getName());
-  private volatile Meter meter;
+  private static volatile Listener listener;
 
-  private static final Object lock = new Object();
+  private volatile Meter meter;
+  private final Object lock = new Object();
 
   @GuardedBy("lock")
-  private static final List<RegisteredObservable> registeredObservables = new ArrayList<>();
+  private final List<RegisteredObservable> registeredObservables = new ArrayList<>();
 
   /**
    * Reset for test by resetting the {@link #meter} to {@code null} and closing all registered
    * instruments.
    */
-  static void resetForTest() {
+  void resetForTest() {
     closeAllInstruments();
   }
 
   // Visible for test
-  static List<RegisteredObservable> getRegisteredObservables() {
+  List<RegisteredObservable> getRegisteredObservables() {
     synchronized (lock) {
       return new ArrayList<>(registeredObservables);
     }
   }
 
+  public OpenTelemetryMetricsReporter() {
+    if (listener != null) {
+      listener.metricsReporterCreated(this);
+    }
+  }
+
   @Override
   public void init(List<KafkaMetric> metrics) {
     metrics.forEach(this::metricChange);
@@ -131,7 +138,7 @@ public final class OpenTelemetryMetricsReporter implements MetricsReporter {
     closeAllInstruments();
   }
 
-  private static void closeAllInstruments() {
+  private void closeAllInstruments() {
     synchronized (lock) {
       for (Iterator<RegisteredObservable> it = registeredObservables.iterator(); it.hasNext(); ) {
         closeInstrument(it.next().getObservable());
@@ -177,4 +184,14 @@ public final class OpenTelemetryMetricsReporter implements MetricsReporter {
     }
     return (T) value;
   }
+
+  // Visible for test
+  static void setListener(Listener listener) {
+    OpenTelemetryMetricsReporter.listener = listener;
+  }
+
+  // used for testing
+  interface Listener {
+    void metricsReporterCreated(OpenTelemetryMetricsReporter metricsReporter);
+  }
 }