YARN-10194. YARN RMWebServices /scheduler-conf/validate leaks ZK Connections. Contributed by Prabhu Joseph

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

@@ -42,14 +42,18 @@ public final class CapacitySchedulerConfigValidator {
   public static boolean validateCSConfiguration(
           final Configuration oldConf, final Configuration newConf,
           final RMContext rmContext) throws IOException {
+    CapacityScheduler newCs = new CapacityScheduler();
+    try {
       //TODO: extract all the validation steps and replace reinitialize with
       //the specific validation steps
-    CapacityScheduler newCs = new CapacityScheduler();
       newCs.setConf(oldConf);
       newCs.setRMContext(rmContext);
       newCs.init(oldConf);
       newCs.reinitialize(newConf, rmContext, true);
       return true;
+    } finally {
+      newCs.stop();
+    }
   }
 
   public static Set<String> validatePlacementRules(

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

@@ -358,6 +358,7 @@ public class FSSchedulerConfigurationStore extends YarnConfigurationStore {
     return CURRENT_VERSION_INFO;
   }
 
+  @Override
   public void close() throws IOException {
     if (fileSystem != null) {
       fileSystem.close();

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

@@ -22,6 +22,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.yarn.server.records.Version;
 import org.apache.hadoop.yarn.server.resourcemanager.RMContext;
 
+import java.io.IOException;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -150,4 +151,9 @@ public class InMemoryConfigurationStore extends YarnConfigurationStore {
   public void checkVersion() {
     // Does nothing. (Version is always compatible since it's in memory)
   }
+
+  @Override
+  public void close() throws IOException {
+    // Does nothing.
+  }
 }

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

@@ -99,7 +99,7 @@ public abstract class YarnConfigurationStore {
    * Closes the configuration store, releasing any required resources.
    * @throws IOException on failure to close
    */
-  public void close() throws IOException {}
+  public abstract void close() throws IOException;
 
   /**
    * Logs the configuration change to backing store.

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

@@ -31,6 +31,7 @@ import org.apache.hadoop.yarn.server.resourcemanager.RMContext;
 import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.data.ACL;
 
+import java.io.IOException;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.ObjectInputStream;
@@ -316,4 +317,11 @@ public class ZKConfigurationStore extends YarnConfigurationStore {
   private static <T> T unsafeCast(Object o) throws ClassCastException {
     return (T)o;
   }
+
+  @Override
+  public void close() throws IOException {
+    if (zkManager  != null) {
+      zkManager.close();
+    }
+  }
 }