Add log statement

Signed-off-by: Anshu Agarwal <anshukag@amazon.com>

server/src/main/java/org/opensearch/cluster/routing/IndexShardRoutingTable.java

@@ -32,6 +32,8 @@
 
 package org.opensearch.cluster.routing;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.opensearch.cluster.node.DiscoveryNode;
 import org.opensearch.cluster.node.DiscoveryNodes;
 import org.opensearch.common.Nullable;
@@ -90,6 +92,8 @@ public class IndexShardRoutingTable implements Iterable<ShardRouting> {
     private volatile Map<WeightedRoutingKey, List<ShardRouting>> activeShardsByWeight = emptyMap();
     private volatile Map<WeightedRoutingKey, List<ShardRouting>> initializingShardsByWeight = emptyMap();
 
+    private static final Logger logger = LogManager.getLogger(IndexShardRoutingTable.class);
+
     /**
      * The initializing list, including ones that are initializing on a target node because of relocation.
      * If we can come up with a better variable name, it would be nice...
@@ -336,7 +340,7 @@ public ShardIterator activeInitializingShardsWeightedIt(WeightedRouting weighted
         } catch (IllegalArgumentException e) {
             // this exception is thrown by {@link onlyNodeSelectorActiveInitializingShardsIt} in case count of shard
             // copies found is zero
-            System.out.println();
+            logger.debug("no shard copies found for shard id [{}] for node attribute with weight zero", shardId);
         }
 
         return new PlainShardIterator(shardId, ordered);