JAVA-3077: ListenersIT intermittently failing with: Wanted but not in…

…voked: schemaListener1.onSessionReady (#1670)

ListenersIT.java:
- Add 500ms wait on SchemaListener#onSessionReady call verification
- Add latch to wait for MySchemaChangeListener#onSessionReady
- Add some comments around which listeners/methods need synchronizations and why/not

integration-tests/src/test/java/com/datastax/oss/driver/core/session/ListenersIT.java

@@ -17,6 +17,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.timeout;
 import static org.mockito.Mockito.verify;
 
 import com.datastax.oss.driver.api.core.CqlSession;
@@ -33,9 +34,12 @@
 import com.datastax.oss.driver.api.testinfra.session.SessionUtils;
 import com.datastax.oss.driver.api.testinfra.simulacron.SimulacronRule;
 import com.datastax.oss.driver.categories.ParallelizableTests;
+import com.datastax.oss.driver.shaded.guava.common.util.concurrent.Uninterruptibles;
 import com.datastax.oss.simulacron.common.cluster.ClusterSpec;
 import edu.umd.cs.findbugs.annotations.NonNull;
 import java.util.Collections;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 import org.junit.ClassRule;
 import org.junit.Test;
 import org.junit.experimental.categories.Category;
@@ -90,6 +94,9 @@ public void should_inject_session_in_listeners() throws Exception {
                         .build())
                 .build()) {
 
+      // These NodeStateListeners are wrapped with SafeInitNodeStateListener which delays #onUp
+      // callbacks until #onSessionReady is called, these will all happen during session
+      // initialization
       InOrder inOrder1 = inOrder(nodeListener1);
       inOrder1.verify(nodeListener1).onSessionReady(session);
       inOrder1.verify(nodeListener1).onUp(nodeCaptor1.capture());
@@ -104,20 +111,29 @@ public void should_inject_session_in_listeners() throws Exception {
       assertThat(nodeCaptor2.getValue().getEndPoint())
           .isEqualTo(SIMULACRON_RULE.getContactPoints().iterator().next());
 
-      verify(schemaListener1).onSessionReady(session);
-      verify(schemaListener2).onSessionReady(session);
+      // SchemaChangeListener#onSessionReady is called asynchronously from AdminExecutor so we may
+      // have to wait a little
+      verify(schemaListener1, timeout(500).times(1)).onSessionReady(session);
+      verify(schemaListener2, timeout(500).times(1)).onSessionReady(session);
 
+      // Request tracker #onSessionReady is called synchronously during session initialization
       verify(requestTracker1).onSessionReady(session);
       verify(requestTracker2).onSessionReady(session);
 
       assertThat(MyNodeStateListener.onSessionReadyCalled).isTrue();
       assertThat(MyNodeStateListener.onUpCalled).isTrue();
 
-      assertThat(MySchemaChangeListener.onSessionReadyCalled).isTrue();
+      // SchemaChangeListener#onSessionReady is called asynchronously from AdminExecutor so we may
+      // have to wait a little
+      assertThat(
+              Uninterruptibles.awaitUninterruptibly(
+                  MySchemaChangeListener.onSessionReadyLatch, 500, TimeUnit.MILLISECONDS))
+          .isTrue();
 
       assertThat(MyRequestTracker.onSessionReadyCalled).isTrue();
     }
 
+    // CqlSession#close waits for all listener close methods to be called
     verify(nodeListener1).close();
     verify(nodeListener2).close();
 
@@ -163,14 +179,14 @@ public void close() {
 
   public static class MySchemaChangeListener extends SchemaChangeListenerBase {
 
-    private static volatile boolean onSessionReadyCalled = false;
+    private static CountDownLatch onSessionReadyLatch = new CountDownLatch(1);
     private static volatile boolean closeCalled = false;
 
     public MySchemaChangeListener(@SuppressWarnings("unused") DriverContext ignored) {}
 
     @Override
     public void onSessionReady(@NonNull Session session) {
-      onSessionReadyCalled = true;
+      onSessionReadyLatch.countDown();
     }
 
     @Override