Make addMissingChannels use advanced shard awareness

It will now specify target shard when connecting.

Author: Bouncheck

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

@@ -489,9 +489,21 @@ private CompletionStage<Boolean> addMissingChannels() {
           channels.length * wantedCount - Arrays.stream(channels).mapToInt(ChannelSet::size).sum();
       LOG.debug("[{}] Trying to create {} missing channels", logPrefix, missing);
       DriverChannelOptions options = buildDriverOptions();
-      for (int i = 0; i < missing; i++) {
-        CompletionStage<DriverChannel> channelFuture = channelFactory.connect(node, options);
-        pendingChannels.add(channelFuture);
+      for (int shard = 0; shard < channels.length; shard++) {
+        LOG.trace(
+            "[{}] Missing {} channels for shard {}",
+            logPrefix,
+            wantedCount - channels[shard].size(),
+            shard);
+        for (int p = channels[shard].size(); p < wantedCount; p++) {
+          CompletionStage<DriverChannel> channelFuture;
+          if (node.getShardingInfo() != null) {
+            channelFuture = channelFactory.connect(node, shard, options);
+          } else {
+            channelFuture = channelFactory.connect(node, options);
+          }
+          pendingChannels.add(channelFuture);
+        }
       }
       return CompletableFutures.allDone(pendingChannels)
           .thenApplyAsync(this::onAllConnected, adminExecutor);