YARN-9394. Use new API of RackResolver to get better performance. Contributed by Lantao Jin.

(cherry picked from commit 945e8c60640ceb938ad8d27767d44eec53a15038)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-client/src/main/java/org/apache/hadoop/yarn/client/api/impl/AMRMClientImpl.java

@@ -40,6 +40,7 @@ import org.apache.hadoop.classification.InterfaceStability.Unstable;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.net.Node;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.yarn.api.ApplicationMasterProtocol;
 import org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest;
@@ -763,10 +764,11 @@ public class AMRMClientImpl<T extends ContainerRequest> extends AMRMClient<T> {
   private Set<String> resolveRacks(List<String> nodes) {
     Set<String> racks = new HashSet<String>();    
     if (nodes != null) {
-      for (String node : nodes) {
+      List<Node> tmpList = RackResolver.resolve(nodes);
+      for (Node node : tmpList) {
+        String rack = node.getNetworkLocation();
         // Ensure node requests are accompanied by requests for
         // corresponding rack
-        String rack = RackResolver.resolve(node).getNetworkLocation();
         if (rack == null) {
           LOG.warn("Failed to resolve rack for node " + node + ".");
         } else {
@@ -774,7 +776,6 @@ public class AMRMClientImpl<T extends ContainerRequest> extends AMRMClient<T> {
         }
       }
     }
-    
     return racks;
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-client/src/test/java/org/apache/hadoop/yarn/client/api/impl/TestAMRMClientContainerRequest.java

@@ -20,7 +20,7 @@ package org.apache.hadoop.yarn.client.api.impl;
 
 import static org.junit.Assert.assertEquals;
 
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.hadoop.conf.Configuration;
@@ -254,7 +254,7 @@ public class TestAMRMClientContainerRequest {
 
     @Override
     public List<String> resolve(List<String> names) {
-      return Arrays.asList("/rack1");
+      return Collections.nCopies(names.size(), "/rack1");
     }
 
     @Override