YARN-10375. CS Mapping rule config parser should return MappingRule objects. Contributed by Gergely Pollak.

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

@@ -21,6 +21,7 @@ package org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableSet;
+import org.apache.hadoop.yarn.server.resourcemanager.placement.MappingRule;
 import org.apache.hadoop.yarn.server.resourcemanager.placement.QueuePlacementRuleUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -279,6 +280,10 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
   @Private
   public static final String QUEUE_MAPPING = PREFIX + "queue-mappings";
 
+  @Private
+  public static final String QUEUE_MAPPING_NAME =
+      YarnConfiguration.QUEUE_PLACEMENT_RULES + ".app-name";
+
   @Private
   public static final String ENABLE_QUEUE_MAPPING_OVERRIDE = QUEUE_MAPPING + "-override.enable";
 
@@ -1159,6 +1164,46 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
     return mappings;
   }
 
+  public List<MappingRule> getMappingRules() {
+    List<MappingRule> mappings = new ArrayList<MappingRule>();
+    Collection<String> mappingsString =
+        getTrimmedStringCollection(QUEUE_MAPPING);
+
+    for (String mappingValue : mappingsString) {
+      String[] mapping =
+          StringUtils.getTrimmedStringCollection(mappingValue, ":")
+              .toArray(new String[] {});
+      if (mapping.length != 3 || mapping[1].length() == 0
+          || mapping[2].length() == 0) {
+        throw new IllegalArgumentException(
+            "Illegal queue mapping " + mappingValue);
+      }
+
+      if (mapping[0].equals("u") || mapping[0].equals("g")) {
+        mappings.add(MappingRule.createLegacyRule(
+            mapping[0], mapping[1], mapping[2]));
+      } else {
+        throw new IllegalArgumentException(
+            "unknown mapping prefix " + mapping[0]);
+      }
+    }
+
+    mappingsString = getTrimmedStringCollection(QUEUE_MAPPING_NAME);
+    for (String mappingValue : mappingsString) {
+      String[] mapping =
+          StringUtils.getTrimmedStringCollection(mappingValue, ":")
+              .toArray(new String[] {});
+      if (mapping.length != 2 || mapping[1].length() == 0) {
+        throw new IllegalArgumentException(
+            "Illegal queue mapping " + mappingValue);
+      }
+
+      mappings.add(MappingRule.createLegacyRule(mapping[0], mapping[1]));
+    }
+
+    return mappings;
+  }
+
   @Private
   @VisibleForTesting
   public void setQueuePlacementRules(Collection<String> queuePlacementRules) {