CASSANDRA-19457: Object reference in Micrometer metrics prevent GC from reclaiming Session instances

core/src/main/java/com/datastax/oss/driver/internal/core/metrics/AbstractMetricUpdater.java

@@ -180,6 +180,4 @@ protected Timeout newTimeout() {
  expireAfter.toNanos(),
  TimeUnit.NANOSECONDS);
  }
-
- protected abstract void clearMetrics();
 }

core/src/main/java/com/datastax/oss/driver/internal/core/metrics/DropwizardMetricUpdater.java

@@ -91,7 +91,7 @@ public void updateTimer(
  }
 
  @Override
-protected void clearMetrics() {
+public void clearMetrics() {
  for (MetricT metric : metrics.keySet()) {
  MetricId id = getMetricId(metric);
  registry.remove(id.getName());

core/src/main/java/com/datastax/oss/driver/internal/core/metrics/MetricUpdater.java

@@ -46,4 +46,6 @@ default void markMeter(MetricT metric, @Nullable String profileName) {
  void updateTimer(MetricT metric, @Nullable String profileName, long duration, TimeUnit unit);
 
  boolean isEnabled(MetricT metric, @Nullable String profileName);
+
+ void clearMetrics();
 }

core/src/main/java/com/datastax/oss/driver/internal/core/metrics/NoopNodeMetricUpdater.java

@@ -53,4 +53,9 @@ public boolean isEnabled(NodeMetric metric, String profileName) {
  // since methods don't do anything, return false
  return false;
  }
+
+ @Override
+ public void clearMetrics() {
+ // nothing to do
+ }
 }

core/src/main/java/com/datastax/oss/driver/internal/core/metrics/NoopSessionMetricUpdater.java

@@ -53,4 +53,7 @@ public boolean isEnabled(SessionMetric metric, String profileName) {
  // since methods don't do anything, return false
  return false;
  }
+
+ @Override
+ public void clearMetrics() {}
 }

core/src/main/java/com/datastax/oss/driver/internal/core/session/DefaultSession.java

@@ -34,6 +34,7 @@
 import com.datastax.oss.driver.internal.core.channel.DriverChannel;
 import com.datastax.oss.driver.internal.core.context.InternalDriverContext;
 import com.datastax.oss.driver.internal.core.context.LifecycleListener;
+import com.datastax.oss.driver.internal.core.metadata.DefaultNode;
 import com.datastax.oss.driver.internal.core.metadata.MetadataManager;
 import com.datastax.oss.driver.internal.core.metadata.MetadataManager.RefreshSchemaResult;
 import com.datastax.oss.driver.internal.core.metadata.NodeStateEvent;
@@ -546,6 +547,13 @@ private void close() {
 
  closePolicies();
 
+ // clear metrics to prevent memory leak
+ for (Node n : metadataManager.getMetadata().getNodes().values()) {
+ ((DefaultNode) n).getMetricUpdater().clearMetrics();
+ }
+
+ DefaultSession.this.metricUpdater.clearMetrics();
+
  List<CompletionStage<Void>> childrenCloseStages = new ArrayList<>();
  for (AsyncAutoCloseable closeable : internalComponentsToClose()) {
  childrenCloseStages.add(closeable.closeAsync());
@@ -565,6 +573,13 @@ private void forceClose() {
  logPrefix,
  (closeWasCalled ? "" : "not "));
 
+ // clear metrics to prevent memory leak
+ for (Node n : metadataManager.getMetadata().getNodes().values()) {
+ ((DefaultNode) n).getMetricUpdater().clearMetrics();
+ }
+
+ DefaultSession.this.metricUpdater.clearMetrics();
+
  if (closeWasCalled) {
  // onChildrenClosed has already been scheduled
  for (AsyncAutoCloseable closeable : internalComponentsToClose()) {

integration-tests/src/test/java/com/datastax/oss/driver/core/metrics/DropwizardMetricsIT.java

@@ -198,6 +198,12 @@ protected void assertNodeMetricsNotEvicted(CqlSession session, Node node) {
  }
  }
 
+ @Override
+ protected void assertMetricsNotPresent(Object registry) {
+ MetricRegistry dropwizardRegistry = (MetricRegistry) registry;
+ assertThat(dropwizardRegistry.getMetrics()).isEmpty();
+ }
+
  @Override
  protected void assertNodeMetricsEvicted(CqlSession session, Node node) {
  InternalDriverContext context = (InternalDriverContext) session.getContext();

integration-tests/src/test/java/com/datastax/oss/driver/core/metrics/MetricsITBase.java

@@ -83,8 +83,10 @@ public void resetSimulacron() {
 
  @Test
  @UseDataProvider("descriptorsAndPrefixes")
- public void should_expose_metrics_if_enabled(Class<?> metricIdGenerator, String prefix) {
+ public void should_expose_metrics_if_enabled_and_clear_metrics_if_closed(
+ Class<?> metricIdGenerator, String prefix) {
 
+ Object registry = newMetricRegistry();
  Assume.assumeFalse(
  "Cannot use metric tags with Dropwizard",
  metricIdGenerator.getSimpleName().contains("Tagging")
@@ -101,12 +103,14 @@ public void should_expose_metrics_if_enabled(Class<?> metricIdGenerator, String
  CqlSession.builder()
  .addContactEndPoints(simulacron().getContactPoints())
  .withConfigLoader(loader)
- .withMetricRegistry(newMetricRegistry())
+ .withMetricRegistry(registry)
  .build()) {
 
  session.prepare("irrelevant");
  queryAllNodes(session);
  assertMetricsPresent(session);
+ } finally {
+ assertMetricsNotPresent(registry);
  }
  }
 
@@ -262,4 +266,6 @@ private DefaultNode findNode(CqlSession session, int id) {
  return (DefaultNode)
  session.getMetadata().findNode(address1).orElseThrow(IllegalStateException::new);
  }
+
+ protected abstract void assertMetricsNotPresent(Object registry);
 }

integration-tests/src/test/java/com/datastax/oss/driver/metrics/micrometer/MicrometerMetricsIT.java

@@ -186,6 +186,12 @@ protected void assertNodeMetricsNotEvicted(CqlSession session, Node node) {
  }
  }
 
+ @Override
+ protected void assertMetricsNotPresent(Object registry) {
+ MeterRegistry micrometerRegistry = (MeterRegistry) registry;
+ assertThat(micrometerRegistry.getMeters()).isEmpty();
+ }
+
  @Override
  protected void assertNodeMetricsEvicted(CqlSession session, Node node) {
  InternalDriverContext context = (InternalDriverContext) session.getContext();

integration-tests/src/test/java/com/datastax/oss/driver/metrics/microprofile/MicroProfileMetricsIT.java

@@ -188,6 +188,12 @@ protected void assertNodeMetricsNotEvicted(CqlSession session, Node node) {
  }
  }
 
+ @Override
+ protected void assertMetricsNotPresent(Object registry) {
+ MetricRegistry metricRegistry = (MetricRegistry) registry;
+ assertThat(metricRegistry.getMetrics()).isEmpty();
+ }
+
  @Override
  protected void assertNodeMetricsEvicted(CqlSession session, Node node) {
  InternalDriverContext context = (InternalDriverContext) session.getContext();

metrics/micrometer/src/main/java/com/datastax/oss/driver/internal/metrics/micrometer/MicrometerMetricUpdater.java

@@ -83,7 +83,7 @@ public void updateTimer(
  }
 
  @Override
-protected void clearMetrics() {
+public void clearMetrics() {
  for (Meter metric : metrics.values()) {
  registry.remove(metric);
  }

metrics/microprofile/src/main/java/com/datastax/oss/driver/internal/metrics/microprofile/MicroProfileMetricUpdater.java

@@ -83,7 +83,7 @@ public void updateTimer(
  }
 
  @Override
-protected void clearMetrics() {
+public void clearMetrics() {
  for (MetricT metric : metrics.keySet()) {
  MetricId id = getMetricId(metric);
  Tag[] tags = MicroProfileTags.toMicroProfileTags(id.getTags());