Fix NPE in ChannelPool metrics methods when pool is uninitialized

core/src/main/java/com/datastax/oss/driver/internal/core/pool/ChannelPool.java

@@ -210,11 +210,17 @@ public DriverChannel next(@Nullable Token routingKey, @Nullable Integer shardSug
 
   /** @return the number of active channels in the pool. */
   public int size() {
+    if (!singleThreaded.initialized) {
+      return 0;
+    }
     return Arrays.stream(channels).mapToInt(ChannelSet::size).sum();
   }
 
   /** @return the number of available stream ids on all channels in the pool. */
   public int getAvailableIds() {
+    if (!singleThreaded.initialized) {
+      return 0;
+    }
     return Arrays.stream(channels).mapToInt(ChannelSet::getAvailableIds).sum();
   }
 
@@ -223,6 +229,9 @@ public int getAvailableIds() {
    *     {@link #getOrphanedIds() orphaned ids}).
    */
   public int getInFlight() {
+    if (!singleThreaded.initialized) {
+      return 0;
+    }
     return Arrays.stream(channels).mapToInt(ChannelSet::getInFlight).sum();
   }
 
@@ -232,6 +241,9 @@ public int getInFlight() {
    *     might still come from the server.
    */
   public int getOrphanedIds() {
+    if (!singleThreaded.initialized) {
+      return 0;
+    }
     return Arrays.stream(channels).mapToInt(ChannelSet::getOrphanedIds).sum();
   }
 

core/src/test/java/com/datastax/oss/driver/internal/core/pool/ChannelPoolInitTest.java

@@ -148,6 +148,34 @@ public void should_fire_force_down_event_when_cluster_name_does_not_match() thro
     factoryHelper.verifyNoMoreCalls();
   }
 
+  @Test
+  public void should_return_zero_for_metric_accessors_when_pool_uninitialized() throws Exception {
+    // Reproduce CUSTOMER-413: when the initial connection attempt fails, connectFuture completes
+    // with channels == null (initialize() is only called on the success path). Before the fix,
+    // any call to size/getAvailableIds/getInFlight/getOrphanedIds threw NullPointerException via
+    // Arrays.stream(null), which propagated through the Dropwizard Metrics gauge lambdas
+    // registered in DropwizardNodeMetricUpdater.
+    when(defaultProfile.getInt(DefaultDriverOption.CONNECTION_POOL_LOCAL_SIZE)).thenReturn(1);
+
+    MockChannelFactoryHelper.builder(channelFactory)
+        .failure(node, "mock channel init failure")
+        .build();
+
+    CompletionStage<ChannelPool> poolFuture =
+        ChannelPool.init(node, null, NodeDistance.LOCAL, context, "test");
+
+    ChannelPool pool = poolFuture.toCompletableFuture().get();
+
+    // Confirm the precondition: pool entered the map but channels was never initialized
+    assertThat(pool.channels).isNull();
+
+    // All four accessor methods must return 0 without throwing
+    assertThat(pool.size()).isEqualTo(0);
+    assertThat(pool.getAvailableIds()).isEqualTo(0);
+    assertThat(pool.getInFlight()).isEqualTo(0);
+    assertThat(pool.getOrphanedIds()).isEqualTo(0);
+  }
+
   @Test
   public void should_reconnect_when_init_incomplete() throws Exception {
     // Short delay so we don't have to wait in the test