YARN-10600. Convert root queue in fs2cs weight mode conversion. Contributed by Benjamin Teke.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/converter/weightconversion/WeightToWeightConverter.java

@@ -28,6 +28,7 @@ import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSQueue;
 
 public class WeightToWeightConverter
     implements CapacityConverter {
+  private static final String ROOT_QUEUE = "root";
 
   @Override
   public void convertWeightsForChildQueues(FSQueue queue,
@@ -35,6 +36,10 @@ public class WeightToWeightConverter
     List<FSQueue> children = queue.getChildQueues();
 
     if (queue instanceof FSParentQueue || !children.isEmpty()) {
+      if (queue.getName().equals(ROOT_QUEUE)) {
+        csConfig.set(getProperty(queue), getWeightString(queue));
+      }
+
       children.forEach(fsQueue -> csConfig.set(
           getProperty(fsQueue), getWeightString(fsQueue)));
       csConfig.setBoolean(getAutoCreateV2EnabledProperty(queue), true);

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/converter/weightconversion/TestWeightToWeightConverter.java

@@ -44,7 +44,9 @@ public class TestWeightToWeightConverter extends WeightConverterTestBase {
     FSQueue root = createFSQueues();
     converter.convertWeightsForChildQueues(root, config);
 
-    assertEquals("Converted items", 1,
+    assertEquals("root weight", "1.0w",
+        config.get(PREFIX + "root.capacity"));
+    assertEquals("Converted items", 2,
         config.getPropsWithPrefix(PREFIX).size());
   }
 
@@ -53,9 +55,11 @@ public class TestWeightToWeightConverter extends WeightConverterTestBase {
     FSQueue root = createFSQueues(1);
     converter.convertWeightsForChildQueues(root, config);
 
+    assertEquals("root weight", "1.0w",
+        config.get(PREFIX + "root.capacity"));
     assertEquals("root.a weight", "1.0w",
         config.get(PREFIX + "root.a.capacity"));
-    assertEquals("Number of properties", 2,
+    assertEquals("Number of properties", 3,
         config.getPropsWithPrefix(PREFIX).size());
   }
 
@@ -65,8 +69,10 @@ public class TestWeightToWeightConverter extends WeightConverterTestBase {
 
     converter.convertWeightsForChildQueues(root, config);
 
-    assertEquals("Number of properties", 4,
+    assertEquals("Number of properties", 5,
         config.getPropsWithPrefix(PREFIX).size());
+    assertEquals("root weight", "1.0w",
+        config.get(PREFIX + "root.capacity"));
     assertEquals("root.a weight", "1.0w",
         config.get(PREFIX + "root.a.capacity"));
     assertEquals("root.b weight", "2.0w",
@@ -90,7 +96,7 @@ public class TestWeightToWeightConverter extends WeightConverterTestBase {
     FSQueue root = createParent(new ArrayList<>());
     converter.convertWeightsForChildQueues(root, config);
 
-    assertEquals("Number of properties", 1,
+    assertEquals("Number of properties", 2,
         config.getPropsWithPrefix(PREFIX).size());
     assertTrue("root autocreate v2 enabled",
         config.getBoolean(PREFIX + "root.auto-queue-creation-v2.enabled",