/**
 * 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.reservation;

import java.io.IOException;
import java.util.Collection;
import java.util.List;

import org.apache.hadoop.yarn.api.records.ReservationId;
import org.apache.hadoop.yarn.api.records.Resource;
import org.apache.hadoop.yarn.exceptions.YarnRuntimeException;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.Queue;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.ResourceScheduler;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.SchedulerDynamicEditException;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CSQueue;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.PlanQueue;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.ReservationQueue;
import org.apache.hadoop.yarn.util.Clock;
import org.apache.hadoop.yarn.util.resource.Resources;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class implements a {@link PlanFollower}. This is invoked on a timer, and
 * it is in charge to publish the state of the {@link Plan}s to the underlying
 * {@link CapacityScheduler}. This implementation does so, by
 * adding/removing/resizing leaf queues in the scheduler, thus affecting the
 * dynamic behavior of the scheduler in a way that is consistent with the
 * content of the plan. It also updates the plan's view on how much resources
 * are available in the cluster.
 * 
 * This implementation of PlanFollower is relatively stateless, and it can
 * synchronize schedulers and Plans that have arbitrary changes (performing set
 * differences among existing queues). This makes it resilient to frequency of
 * synchronization, and RM restart issues (no "catch up" is necessary).
 */
public class CapacitySchedulerPlanFollower extends AbstractSchedulerPlanFollower {

  private static final Logger LOG = LoggerFactory
      .getLogger(CapacitySchedulerPlanFollower.class);

  private CapacityScheduler cs;

  @Override
  public void init(Clock clock, ResourceScheduler sched, Collection<Plan> plans) {
    super.init(clock, sched, plans);
    LOG.info("Initializing Plan Follower Policy:"
        + this.getClass().getCanonicalName());
    if (!(sched instanceof CapacityScheduler)) {
      throw new YarnRuntimeException(
          "CapacitySchedulerPlanFollower can only work with CapacityScheduler");
    }
    this.cs = (CapacityScheduler) sched;
  }

  @Override
  protected Queue getPlanQueue(String planQueueName) {
    CSQueue queue = cs.getQueue(planQueueName);
    if (!(queue instanceof PlanQueue)) {
      LOG.error("The Plan is not an PlanQueue!");
      return null;
    }
    return queue;
  }

  @Override
  protected List<? extends Queue> getChildReservationQueues(Queue queue) {
    PlanQueue planQueue = (PlanQueue)queue;
    List<CSQueue> childQueues = planQueue.getChildQueues();
    return childQueues;
  }

  @Override
  protected void addReservationQueue(
      String planQueueName, Queue queue, String currResId) {
    PlanQueue planQueue = (PlanQueue)queue;
    try {
      ReservationQueue resQueue =
          new ReservationQueue(cs, currResId, planQueue);
      cs.addQueue(resQueue);
    } catch (SchedulerDynamicEditException e) {
      LOG.warn(
          "Exception while trying to activate reservation: {} for plan: {}",
          currResId, planQueueName, e);
    } catch (IOException e) {
      LOG.warn(
          "Exception while trying to activate reservation: {} for plan: {}",
          currResId, planQueueName, e);
    }
  }

  @Override
  protected void createDefaultReservationQueue(
      String planQueueName, Queue queue, String defReservationId) {
    PlanQueue planQueue = (PlanQueue)queue;
    if (cs.getQueue(defReservationId) == null) {
      try {
        ReservationQueue defQueue =
            new ReservationQueue(cs, defReservationId, planQueue);
        cs.addQueue(defQueue);
      } catch (SchedulerDynamicEditException e) {
        LOG.warn(
            "Exception while trying to create default reservation queue for plan: {}",
            planQueueName, e);
      } catch (IOException e) {
        LOG.warn(
            "Exception while trying to create default reservation queue for " +
                "plan: {}",
            planQueueName, e);
      }
    }
  }

  @Override
  protected Resource getPlanResources(
      Plan plan, Queue queue, Resource clusterResources) {
    PlanQueue planQueue = (PlanQueue)queue;
    float planAbsCap = planQueue.getAbsoluteCapacity();
    Resource planResources = Resources.multiply(clusterResources, planAbsCap);
    plan.setTotalCapacity(planResources);
    return planResources;
  }

  @Override
  protected Resource getReservationQueueResourceIfExists(Plan plan,
      ReservationId reservationId) {
    CSQueue resQueue = cs.getQueue(reservationId.toString());
    Resource reservationResource = null;
    if (resQueue != null) {
      reservationResource = Resources.multiply(cs.getClusterResource(),
          resQueue.getAbsoluteCapacity());
    }
    return reservationResource;
  }

}