Support a case when the cluster could be behind a load-balancer

core/src/main/java/com/datastax/oss/driver/internal/core/cql/CqlRequestHandler.java

@@ -51,6 +51,7 @@
 import com.datastax.oss.driver.internal.core.metadata.DefaultNode;
 import com.datastax.oss.driver.internal.core.metrics.NodeMetricUpdater;
 import com.datastax.oss.driver.internal.core.metrics.SessionMetricUpdater;
+import com.datastax.oss.driver.internal.core.pool.ChannelPool;
 import com.datastax.oss.driver.internal.core.session.DefaultSession;
 import com.datastax.oss.driver.internal.core.session.RepreparePayload;
 import com.datastax.oss.driver.internal.core.tracker.NoopRequestTracker;
@@ -108,6 +109,7 @@ public class CqlRequestHandler implements Throttled {
   protected final CompletableFuture<AsyncResultSet> result;
   private final Message message;
   private final Timer timer;
+  private Boolean retryFailedSend = true;
   /**
    * How many speculative executions are currently running (including the initial execution). We
    * track this in order to know when to fail the request if all executions have reached the end of
@@ -505,17 +507,28 @@ public void operationComplete(Future<java.lang.Void> future) throws Exception {
           setFinalError(error.getCause(), node, execution);
         } else {
           LOG.trace(
-              "[{}] Failed to send request on {}, trying next node (cause: {})",
+              "[{}] Failed to send request on {}, trying next node (cause: {}), queryPlan: {}, retryFailedSend: {}",
               logPrefix,
               channel,
-              error);
+              error,
+              queryPlan,
+              retryFailedSend);
+          Node retriedNode = null;
+          if (queryPlan.size() == 0 && retryFailedSend) {
+            retryFailedSend = false;
+            // No nodes left, but checking if any connections still available
+            ChannelPool p = session.getPools().get(node);
+            if (p != null && p.size() > 0) {
+              LOG.trace("Trying node {} one more time since it still has few connections", node);
+              retriedNode = node;
+            }
+          }
           recordError(node, error);
           trackNodeError(node, error, NANOTIME_NOT_MEASURED_YET);
           ((DefaultNode) node)
               .getMetricUpdater()
               .incrementCounter(DefaultNodeMetric.UNSENT_REQUESTS, executionProfile.getName());
-          sendRequest(
-              null, queryPlan, execution, retryCount, scheduleNextExecution); // try next node
+          sendRequest(retriedNode, queryPlan, execution, retryCount, scheduleNextExecution);
         }
       } else {
         LOG.trace("[{}] Request sent on {}", logPrefix, channel);

core/src/main/java/com/yugabyte/oss/driver/internal/core/loadbalancing/PartitionAwarePolicy.java

@@ -383,20 +383,21 @@ private static void AppendValueToChannel(
           channel.write(value);
           break;
         }
-      case ProtocolConstants.DataType.LIST: {
-        ListType listType = (ListType) type;
-        DataType dataTypeOfListValue = listType.getElementType();
-        int length = value.getInt();
-        for (int j = 0; j < length; j++) {
-          // Appending each element.
-          int size = value.getInt();
-          ByteBuffer buf = value.slice();
-          buf.limit(size);
-          AppendValueToChannel(dataTypeOfListValue, buf, channel);
-          value.position(value.position() + size);
+      case ProtocolConstants.DataType.LIST:
+        {
+          ListType listType = (ListType) type;
+          DataType dataTypeOfListValue = listType.getElementType();
+          int length = value.getInt();
+          for (int j = 0; j < length; j++) {
+            // Appending each element.
+            int size = value.getInt();
+            ByteBuffer buf = value.slice();
+            buf.limit(size);
+            AppendValueToChannel(dataTypeOfListValue, buf, channel);
+            value.position(value.position() + size);
+          }
+          break;
         }
-        break;
-      }
       case ProtocolConstants.DataType.SET:
         {
           SetType setType = (SetType) type;