/**
 * 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;

import org.apache.hadoop.classification.InterfaceAudience.Private;
import org.apache.hadoop.yarn.api.records.ApplicationId;

/**
 * {@link AbstractUsersManager} tracks users in the system.
 */
@Private
public interface AbstractUsersManager {
  /**
   * An application has new outstanding requests.
   *
   * @param user
   *          application user
   * @param applicationId
   *          activated application
   */
  void activateApplication(String user, ApplicationId applicationId);
  /**
   * An application has no more outstanding requests.
   *
   * @param user
   *          application user
   * @param applicationId
   *          deactivated application
   */
  void deactivateApplication(String user, ApplicationId applicationId);

  /**
   * Get number of active users i.e. users with applications which have pending
   * resource requests.
   *
   * @return number of active users
   */
  int getNumActiveUsers();
}