hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/IsResourceManagerActiveServlet.java

/**
 * 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;

import org.apache.hadoop.http.IsActiveServlet;
import org.apache.hadoop.ha.HAServiceProtocol;

/**
 * Used by Load Balancers to find the active ResourceManager.
 */
public class IsResourceManagerActiveServlet extends IsActiveServlet {

  public static final String RM_ATTRIBUTE = "rm";

  @Override
  protected boolean isActive() {
    ResourceManager rm = (ResourceManager)
        getServletContext().getAttribute(RM_ATTRIBUTE);
    RMContext rmContext = rm.getRMContext();
    HAServiceProtocol.HAServiceState state = rmContext.getHAServiceState();
    return state == HAServiceProtocol.HAServiceState.ACTIVE;
  }
}