YARN-10486. FS-CS converter: handle case when weight=0 and allow more lenient capacity checks in Capacity Scheduler. Contributed by Peter Bacsko

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CapacitySchedulerConfiguration.java

@@ -387,6 +387,10 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
 
   public static final int DEFAULT_MAX_PARALLEL_APPLICATIONS = Integer.MAX_VALUE;
 
+  public static final String ALLOW_ZERO_CAPACITY_SUM =
+      "allow-zero-capacity-sum";
+
+  public static final boolean DEFAULT_ALLOW_ZERO_CAPACITY_SUM = false;
   /**
    * Different resource types supported.
    */
@@ -1488,6 +1492,15 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
         : defaultMaxParallelAppsForUser;
   }
 
+  public boolean getAllowZeroCapacitySum(String queue) {
+    return getBoolean(getQueuePrefix(queue)
+        + ALLOW_ZERO_CAPACITY_SUM, DEFAULT_ALLOW_ZERO_CAPACITY_SUM);
+  }
+
+  public void setAllowZeroCapacitySum(String queue, boolean value) {
+    setBoolean(getQueuePrefix(queue)
+        + ALLOW_ZERO_CAPACITY_SUM, value);
+  }
   private static final String PREEMPTION_CONFIG_PREFIX =
       "yarn.resourcemanager.monitor.capacity.preemption.";
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/ParentQueue.java

@@ -95,6 +95,8 @@ public class ParentQueue extends AbstractCSQueue {
 
   private int runnableApps;
 
+  private final boolean allowZeroCapacitySum;
+
   public ParentQueue(CapacitySchedulerContext cs,
       String queueName, CSQueue parent, CSQueue old) throws IOException {
     super(cs, queueName, parent, old);
@@ -111,6 +113,8 @@ public class ParentQueue extends AbstractCSQueue {
     }
 
     this.childQueues = new ArrayList<>();
+    this.allowZeroCapacitySum =
+        cs.getConfiguration().getAllowZeroCapacitySum(getQueuePath());
 
     setupQueueConfigs(cs.getClusterResource());
 
@@ -159,7 +163,8 @@ public class ParentQueue extends AbstractCSQueue {
           + aclsString + ", labels=" + labelStrBuilder.toString() + "\n"
           + ", reservationsContinueLooking=" + reservationsContinueLooking
           + ", orderingPolicy=" + getQueueOrderingPolicyConfigName()
-          + ", priority=" + priority);
+          + ", priority=" + priority
+          + ", allowZeroCapacitySum=" + allowZeroCapacitySum);
     } finally {
       writeLock.unlock();
     }
@@ -192,13 +197,31 @@ public class ParentQueue extends AbstractCSQueue {
       }
 
       float delta = Math.abs(1.0f - childCapacities);  // crude way to check
-      // allow capacities being set to 0, and enforce child 0 if parent is 0
-      if ((minResDefaultLabel.equals(Resources.none())
+
+      if (allowZeroCapacitySum) {
+        // If we allow zero capacity for children, only fail if:
+        // Σ(childCapacities) != 1.0f OR Σ(childCapacities) != 0.0f
+        //
+        // Therefore, child queues either add up to 0% or 100%.
+        //
+        // Current capacity doesn't matter, because we apply this logic
+        // regardless of whether the current capacity is zero or not.
+        if (minResDefaultLabel.equals(Resources.none())
+            && (delta > PRECISION && childCapacities > PRECISION)) {
+          LOG.error("Capacity validation check is relaxed for"
+              + " queue {}, but the capacity must be either 0% or 100%",
+              getQueuePath());
+          throw new IllegalArgumentException("Illegal" + " capacity of "
+              + childCapacities + " for children of queue " + queueName);
+        }
+      } else if ((minResDefaultLabel.equals(Resources.none())
           && (queueCapacities.getCapacity() > 0) && (delta > PRECISION))
           || ((queueCapacities.getCapacity() == 0) && (childCapacities > 0))) {
+          // allow capacities being set to 0, and enforce child 0 if parent is 0
         throw new IllegalArgumentException("Illegal" + " capacity of "
             + childCapacities + " for children of queue " + queueName);
       }
+
       // check label capacities
       for (String nodeLabel : queueCapacities.getExistingNodeLabels()) {
         float capacityByLabel = queueCapacities.getCapacity(nodeLabel);
@@ -226,7 +249,24 @@ public class ParentQueue extends AbstractCSQueue {
           Resources.addTo(minRes, queue.getQueueResourceQuotas()
               .getConfiguredMinResource(nodeLabel));
         }
-        if ((minResDefaultLabel.equals(Resources.none()) && capacityByLabel > 0
+
+        float labelDelta = Math.abs(1.0f - sum);
+
+        if (allowZeroCapacitySum) {
+          // Similar to above, we only throw exception if
+          // Σ(childCapacities) != 1.0f OR Σ(childCapacities) != 0.0f
+          if (minResDefaultLabel.equals(Resources.none())
+              && capacityByLabel > 0
+              && (labelDelta > PRECISION && sum > PRECISION)) {
+            LOG.error("Capacity validation check is relaxed for"
+                + " queue {}, but the capacity must be either 0% or 100%",
+                getQueuePath());
+            throw new IllegalArgumentException(
+                "Illegal" + " capacity of " + sum + " for children of queue "
+                    + queueName + " for label=" + nodeLabel);
+          }
+        } else if ((minResDefaultLabel.equals(Resources.none())
+            && capacityByLabel > 0
             && Math.abs(1.0f - sum) > PRECISION)
             || (capacityByLabel == 0) && (sum > 0)) {
           throw new IllegalArgumentException(

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

@@ -19,12 +19,11 @@ package org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.converter;
 import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacitySchedulerConfiguration.PREFIX;
 
 import java.math.BigDecimal;
-import java.math.RoundingMode;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.apache.commons.lang3.tuple.Pair;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.yarn.api.records.Resource;
 import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.ConfigurableResource;
@@ -271,10 +270,22 @@ public class FSQueueConverter {
     List<FSQueue> children = queue.getChildQueues();
 
     int totalWeight = getTotalWeight(children);
-    Map<String, BigDecimal> capacities = getCapacities(totalWeight, children);
+    Pair<Map<String, BigDecimal>, Boolean> result =
+        WeightToCapacityConversionUtil.getCapacities(
+            totalWeight, children, ruleHandler);
+
+    Map<String, BigDecimal> capacities = result.getLeft();
+    boolean shouldAllowZeroSumCapacity = result.getRight();
+
     capacities
         .forEach((key, value) -> capacitySchedulerConfig.set(PREFIX + key +
                 ".capacity", value.toString()));
+
+    if (shouldAllowZeroSumCapacity) {
+      String queueName = queue.getName();
+      capacitySchedulerConfig.setBoolean(
+          PREFIX + queueName + ".allow-zero-capacity-sum", true);
+    }
   }
 
   /**
@@ -294,60 +305,6 @@ public class FSQueueConverter {
     }
   }
 
-  private Map<String, BigDecimal> getCapacities(int totalWeight,
-      List<FSQueue> children) {
-    final BigDecimal hundred = new BigDecimal(100).setScale(3);
-
-    if (children.size() == 0) {
-      return new HashMap<>();
-    } else if (children.size() == 1) {
-      Map<String, BigDecimal> capacity = new HashMap<>();
-      String queueName = children.get(0).getName();
-      capacity.put(queueName, hundred);
-
-      return capacity;
-    } else {
-      Map<String, BigDecimal> capacities = new HashMap<>();
-
-      children
-          .stream()
-          .forEach(queue -> {
-            BigDecimal total = new BigDecimal(totalWeight);
-            BigDecimal weight = new BigDecimal(queue.getWeight());
-            BigDecimal pct = weight
-                              .setScale(5)
-                              .divide(total, RoundingMode.HALF_UP)
-                              .multiply(hundred)
-                              .setScale(3);
-
-            if (Resources.none().compareTo(queue.getMinShare()) != 0) {
-              ruleHandler.handleMinResources();
-            }
-
-            capacities.put(queue.getName(), pct);
-          });
-
-      BigDecimal totalPct = new BigDecimal(0);
-      for (Map.Entry<String, BigDecimal> entry : capacities.entrySet()) {
-        totalPct = totalPct.add(entry.getValue());
-      }
-
-      // fix last value if total != 100.000
-      if (!totalPct.equals(hundred)) {
-        BigDecimal tmp = new BigDecimal(0);
-        for (int i = 0; i < children.size() - 1; i++) {
-          tmp = tmp.add(capacities.get(children.get(i).getQueueName()));
-        }
-
-        String lastQueue = children.get(children.size() - 1).getName();
-        BigDecimal corrected = hundred.subtract(tmp);
-        capacities.put(lastQueue, corrected);
-      }
-
-      return capacities;
-    }
-  }
-
   private int getTotalWeight(List<FSQueue> children) {
     double sum = children
                   .stream()

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

@@ -0,0 +1,144 @@
+/**
+* Licensed to the Apache Software Foundation (ASF) under one
+* or more contributor license agreements.  See the NOTICE file
+* distributed with this work for additional information
+* regarding copyright ownership.  The ASF licenses this file
+* to you under the Apache License, Version 2.0 (the
+* "License"); you may not use this file except in compliance
+* with the License.  You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+package org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.converter;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import org.apache.commons.lang3.tuple.Pair;
+import org.apache.hadoop.thirdparty.com.google.common.annotations.VisibleForTesting;
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSQueue;
+import org.apache.hadoop.yarn.util.resource.Resources;
+
+/**
+ * Utility class that converts Fair Scheduler weights to capacities in
+ * percentages.
+ *
+ * It also makes sure that the sum of the capacities adds up to exactly 100.0.
+ *
+ * There is a special case when one or more queues have a capacity of 0. This
+ * can happen if the weight was originally 0 in the FS configuration. In
+ * this case, we need an extra queue with a capacity of 100.0 to have a valid
+ * CS configuration.
+ */
+final class WeightToCapacityConversionUtil {
+  private static final BigDecimal HUNDRED = new BigDecimal(100).setScale(3);
+  private static final BigDecimal ZERO = new BigDecimal(0).setScale(3);
+
+  private WeightToCapacityConversionUtil() {
+    // no instances
+  }
+
+  @VisibleForTesting
+  static Pair<Map<String, BigDecimal>, Boolean> getCapacities(int totalWeight,
+      List<FSQueue> children, FSConfigToCSConfigRuleHandler ruleHandler) {
+
+    if (children.size() == 0) {
+      return Pair.of(new HashMap<>(), false);
+    } else if (children.size() == 1) {
+      Map<String, BigDecimal> capacity = new HashMap<>();
+      String queueName = children.get(0).getName();
+      capacity.put(queueName, HUNDRED);
+
+      return Pair.of(capacity, false);
+    } else {
+      Map<String, BigDecimal> capacities = new HashMap<>();
+
+      children
+          .stream()
+          .forEach(queue -> {
+            BigDecimal pct;
+
+            if (totalWeight == 0) {
+              pct = ZERO;
+            } else {
+              BigDecimal total = new BigDecimal(totalWeight);
+              BigDecimal weight = new BigDecimal(queue.getWeight());
+              pct = weight
+                  .setScale(5)
+                  .divide(total, RoundingMode.HALF_UP)
+                  .multiply(HUNDRED)
+                  .setScale(3);
+            }
+
+            if (Resources.none().compareTo(queue.getMinShare()) != 0) {
+              ruleHandler.handleMinResources();
+            }
+
+            capacities.put(queue.getName(), pct);
+          });
+
+      BigDecimal totalPct = ZERO;
+      for (Map.Entry<String, BigDecimal> entry : capacities.entrySet()) {
+        totalPct = totalPct.add(entry.getValue());
+      }
+
+      // fix capacities if total != 100.000
+      boolean shouldAllowZeroSumCapacity = false;
+      if (!totalPct.equals(HUNDRED)) {
+        shouldAllowZeroSumCapacity = fixCapacities(capacities, totalPct);
+      }
+
+      return Pair.of(capacities, shouldAllowZeroSumCapacity);
+    }
+  }
+
+  @VisibleForTesting
+  static boolean fixCapacities(Map<String, BigDecimal> capacities,
+      BigDecimal totalPct) {
+    final BigDecimal hundred = new BigDecimal(100).setScale(3);
+    boolean shouldAllowZeroSumCapacity = false;
+
+    // Sort the list so we'll adjust the highest capacity value,
+    // because that will affected less by a small change.
+    // Also, it's legal to have weight = 0 and we have to avoid picking
+    // that value as well.
+    List<Map.Entry<String, BigDecimal>> sortedEntries = capacities
+        .entrySet()
+        .stream()
+        .sorted(new Comparator<Map.Entry<String, BigDecimal>>() {
+          @Override
+          public int compare(Map.Entry<String, BigDecimal> e1,
+              Map.Entry<String, BigDecimal> e2) {
+            return e2.getValue().compareTo(e1.getValue());
+          }
+        })
+        .collect(Collectors.toList());
+
+    String highestCapacityQueue = sortedEntries.get(0).getKey();
+    BigDecimal highestCapacity = sortedEntries.get(0).getValue();
+
+    if (highestCapacity.equals(ZERO)) {
+      // need to set allow-zero-capacity-sum on this queue
+      // because we have zero weights on this level
+      shouldAllowZeroSumCapacity = true;
+    } else {
+      BigDecimal diff = hundred.subtract(totalPct);
+      BigDecimal correctedHighest = highestCapacity.add(diff);
+      capacities.put(highestCapacityQueue, correctedHighest);
+    }
+
+    return shouldAllowZeroSumCapacity;
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestParentQueue.java

@@ -426,6 +426,7 @@ public class TestParentQueue {
   private static final String B1 = "b1";
   private static final String B2 = "b2";
   private static final String B3 = "b3";
+  private static final String B4 = "b4";
   
   private void setupMultiLevelQueues(CapacitySchedulerConfiguration conf) {
     
@@ -676,7 +677,64 @@ public class TestParentQueue {
         CapacitySchedulerConfiguration.ROOT, queues, queues,
         TestUtils.spyHook);
   }
-  
+
+  @Test
+  public void testQueueCapacitySettingParentZeroChildren100pctZeroSumAllowed()
+      throws Exception {
+    // Setup queue configs
+    setupMultiLevelQueues(csConf);
+
+    // set parent capacity to 0 when child is 100
+    // and allow zero capacity sum
+    csConf.setCapacity(Q_B, 0);
+    csConf.setCapacity(Q_A, 60);
+    csConf.setAllowZeroCapacitySum(Q_B, true);
+    CSQueueStore queues = new CSQueueStore();
+    CapacitySchedulerQueueManager.parseQueue(csContext, csConf, null,
+        CapacitySchedulerConfiguration.ROOT, queues, queues,
+        TestUtils.spyHook);
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void testQueueCapacitySettingParentZeroChildren50pctZeroSumAllowed()
+      throws Exception {
+    // Setup queue configs
+    setupMultiLevelQueues(csConf);
+
+    // set parent capacity to 0 when sum(children) is 50
+    // and allow zero capacity sum
+    csConf.setCapacity(Q_B, 0);
+    csConf.setCapacity(Q_A, 100);
+    csConf.setCapacity(Q_B + "." + B1, 10);
+    csConf.setCapacity(Q_B + "." + B2, 20);
+    csConf.setCapacity(Q_B + "." + B3, 20);
+    csConf.setAllowZeroCapacitySum(Q_B, true);
+    CSQueueStore queues = new CSQueueStore();
+    CapacitySchedulerQueueManager.parseQueue(csContext, csConf, null,
+        CapacitySchedulerConfiguration.ROOT, queues, queues,
+        TestUtils.spyHook);
+  }
+
+  @Test
+  public void testQueueCapacitySettingParentNonZeroChildrenZeroSumAllowed()
+      throws Exception {
+    // Setup queue configs
+    setupMultiLevelQueues(csConf);
+
+    // set parent capacity to 10 when sum(children) is 0
+    // and allow zero capacity sum
+    csConf.setCapacity(Q_B, 10);
+    csConf.setCapacity(Q_A, 50);
+    csConf.setCapacity(Q_B + "." + B1, 0);
+    csConf.setCapacity(Q_B + "." + B2, 0);
+    csConf.setCapacity(Q_B + "." + B3, 0);
+    csConf.setAllowZeroCapacitySum(Q_B, true);
+    CSQueueStore queues = new CSQueueStore();
+    CapacitySchedulerQueueManager.parseQueue(csContext, csConf, null,
+        CapacitySchedulerConfiguration.ROOT, queues, queues,
+        TestUtils.spyHook);
+  }
+
   @Test
   public void testQueueCapacityZero() throws Exception {
     // Setup queue configs

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

@@ -68,7 +68,10 @@ public class TestFSQueueConverter {
           "root.admins.alice",
           "root.admins.bob",
           "root.users.joe",
-          "root.users.john");
+          "root.users.john",
+          "root.misc",
+          "root.misc.a",
+          "root.misc.b");
 
   private static final String FILE_PREFIX = "file:";
   private static final String FAIR_SCHEDULER_XML =
@@ -148,7 +151,7 @@ public class TestFSQueueConverter {
     converter.convertQueueHierarchy(rootQueue);
 
     // root children
-    assertEquals("root children", "default,admins,users",
+    assertEquals("root children", "default,admins,users,misc",
         csConfig.get(PREFIX + "root.queues"));
 
     // root.admins children
@@ -167,7 +170,8 @@ public class TestFSQueueConverter {
         Sets.newHashSet("root",
             "root.default",
             "root.admins",
-            "root.users"));
+            "root.users",
+            "root.misc"));
 
     assertNoValueForQueues(leafs, ".queues", csConfig);
   }
@@ -285,6 +289,29 @@ public class TestFSQueueConverter {
         csConfig.get(PREFIX + "root.admins.alice.capacity"));
     assertEquals("root.admins.bob capacity", "25.000",
         csConfig.get(PREFIX + "root.admins.bob.capacity"));
+
+    // root.misc
+    assertEquals("root.misc capacity", "0.000",
+        csConfig.get(PREFIX + "root.misc.capacity"));
+    assertEquals("root.misc.a capacity", "0.000",
+        csConfig.get(PREFIX + "root.misc.a.capacity"));
+    assertEquals("root.misc.b capacity", "0.000",
+        csConfig.get(PREFIX + "root.misc.b.capacity"));
+  }
+
+  @Test
+  public void testZeroSumCapacityValidation() {
+    converter = builder.build();
+
+    converter.convertQueueHierarchy(rootQueue);
+
+    Set<String> noZeroSumAllowedQueues = Sets.difference(ALL_QUEUES,
+        Sets.newHashSet("root.misc"));
+    assertNoValueForQueues(noZeroSumAllowedQueues, ".allow-zero-capacity-sum",
+        csConfig);
+
+    assertTrue("root.misc allow zero capacities", csConfig.getBoolean(
+        PREFIX + "root.misc.allow-zero-capacity-sum", false));
   }
 
   @Test

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

@@ -0,0 +1,194 @@
+/**
+* Licensed to the Apache Software Foundation (ASF) under one
+* or more contributor license agreements.  See the NOTICE file
+* distributed with this work for additional information
+* regarding copyright ownership.  The ASF licenses this file
+* to you under the Apache License, Version 2.0 (the
+* "License"); you may not use this file except in compliance
+* with the License.  You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+package org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.converter;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.lang3.tuple.Pair;
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSQueue;
+import org.apache.hadoop.yarn.util.resource.Resources;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class TestWeightToCapacityConversionUtil {
+  @Mock
+  private FSConfigToCSConfigRuleHandler ruleHandler;
+
+  @Test
+  public void testSingleWeightConversion() {
+    List<FSQueue> queues = createFSQueues(1);
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(1, queues, ruleHandler);
+
+    assertFalse("Capacity zerosum allowed", conversion.getRight());
+    assertEquals("Capacity", new BigDecimal("100.000"),
+        conversion.getLeft().get("root.a"));
+  }
+
+  @Test
+  public void testNoChildQueueConversion() {
+    List<FSQueue> queues = new ArrayList<>();
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(1, queues, ruleHandler);
+
+    assertEquals("Converted items", 0, conversion.getLeft().size());
+  }
+
+  @Test
+  public void testMultiWeightConversion() {
+    List<FSQueue> queues = createFSQueues(1, 2, 3);
+
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(6, queues, ruleHandler);
+
+    Map<String, BigDecimal> capacities = conversion.getLeft();
+
+    assertEquals("Number of queues", 3, capacities.size());
+    // this is no fixing - it's the result of BigDecimal rounding
+    assertEquals("root.a capacity", new BigDecimal("16.667"),
+        capacities.get("root.a"));
+    assertEquals("root.b capacity", new BigDecimal("33.333"),
+        capacities.get("root.b"));
+    assertEquals("root.c capacity", new BigDecimal("50.000"),
+        capacities.get("root.c"));
+  }
+
+  @Test
+  public void testMultiWeightConversionWhenOfThemIsZero() {
+    List<FSQueue> queues = createFSQueues(0, 1, 1);
+
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(2, queues, ruleHandler);
+
+    Map<String, BigDecimal> capacities = conversion.getLeft();
+
+    assertFalse("Capacity zerosum allowed", conversion.getRight());
+    assertEquals("Number of queues", 3, capacities.size());
+    assertEquals("root.a capacity", new BigDecimal("0.000"),
+        capacities.get("root.a"));
+    assertEquals("root.b capacity", new BigDecimal("50.000"),
+        capacities.get("root.b"));
+    assertEquals("root.c capacity", new BigDecimal("50.000"),
+        capacities.get("root.c"));
+  }
+
+  @Test
+  public void testMultiWeightConversionWhenAllOfThemAreZero() {
+    List<FSQueue> queues = createFSQueues(0, 0, 0);
+
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(0, queues, ruleHandler);
+
+    Map<String, BigDecimal> capacities = conversion.getLeft();
+
+    assertEquals("Number of queues", 3, capacities.size());
+    assertTrue("Capacity zerosum allowed", conversion.getRight());
+    assertEquals("root.a capacity", new BigDecimal("0.000"),
+        capacities.get("root.a"));
+    assertEquals("root.b capacity", new BigDecimal("0.000"),
+        capacities.get("root.b"));
+    assertEquals("root.c capacity", new BigDecimal("0.000"),
+        capacities.get("root.c"));
+  }
+
+  @Test
+  public void testCapacityFixingWithThreeQueues() {
+    List<FSQueue> queues = createFSQueues(1, 1, 1);
+
+    Pair<Map<String, BigDecimal>, Boolean> conversion =
+        WeightToCapacityConversionUtil.getCapacities(3, queues, ruleHandler);
+
+    Map<String, BigDecimal> capacities = conversion.getLeft();
+    assertEquals("Number of queues", 3, capacities.size());
+    assertEquals("root.a capacity", new BigDecimal("33.334"),
+        capacities.get("root.a"));
+    assertEquals("root.b capacity", new BigDecimal("33.333"),
+        capacities.get("root.b"));
+    assertEquals("root.c capacity", new BigDecimal("33.333"),
+        capacities.get("root.c"));
+  }
+
+  @Test
+  public void testCapacityFixingWhenTotalCapacityIsGreaterThanHundred() {
+    Map<String, BigDecimal> capacities = new HashMap<>();
+    capacities.put("root.a", new BigDecimal("50.001"));
+    capacities.put("root.b", new BigDecimal("25.500"));
+    capacities.put("root.c", new BigDecimal("25.500"));
+
+    testCapacityFixing(capacities, new BigDecimal("100.001"));
+  }
+
+  @Test
+  public void testCapacityFixWhenTotalCapacityIsLessThanHundred() {
+    Map<String, BigDecimal> capacities = new HashMap<>();
+    capacities.put("root.a", new BigDecimal("49.999"));
+    capacities.put("root.b", new BigDecimal("25.500"));
+    capacities.put("root.c", new BigDecimal("25.500"));
+
+    testCapacityFixing(capacities, new BigDecimal("99.999"));
+  }
+
+  private void testCapacityFixing(Map<String, BigDecimal> capacities,
+      BigDecimal total) {
+    // Note: we call fixCapacities() directly because it makes
+    // testing easier
+    boolean needCapacityValidationRelax =
+        WeightToCapacityConversionUtil.fixCapacities(capacities,
+            total);
+
+    assertFalse("Capacity zerosum allowed", needCapacityValidationRelax);
+    assertEquals("root.a capacity", new BigDecimal("50.000"),
+        capacities.get("root.a"));
+    assertEquals("root.b capacity", new BigDecimal("25.500"),
+        capacities.get("root.b"));
+    assertEquals("root.c capacity", new BigDecimal("25.500"),
+        capacities.get("root.c"));
+  }
+
+  private List<FSQueue> createFSQueues(int... weights){
+    char current = 'a';
+
+    List<FSQueue> queues = new ArrayList<>();
+
+    for (int w : weights) {
+      FSQueue queue = mock(FSQueue.class);
+      when(queue.getWeight()).thenReturn((float)w);
+      when(queue.getName()).thenReturn(
+          "root." + new String(new char[] {current}));
+      when(queue.getMinShare()).thenReturn(Resources.none());
+      current++;
+      queues.add(queue);
+    }
+
+    return queues;
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/resources/fair-scheduler-conversion.xml

@@ -73,6 +73,15 @@
                 <maxAMShare>-1.0</maxAMShare>
             </queue>
         </queue>
+        <queue name="misc" type="parent">
+          <weight>0</weight>
+          <queue name="a">
+            <weight>0</weight>
+          </queue>
+          <queue name="b">
+            <weight>0</weight>
+          </queue>
+        </queue>
     </queue>
     <user name="alice">
       <maxRunningApps>30</maxRunningApps>