helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/constraints/MaxCapacityUsageInstanceConstraint.java

package org.apache.helix.controller.rebalancer.waged.constraints;

/*
 * 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.
 */

import org.apache.helix.controller.rebalancer.waged.model.AssignableNode;
import org.apache.helix.controller.rebalancer.waged.model.AssignableReplica;
import org.apache.helix.controller.rebalancer.waged.model.ClusterContext;

/**
 * The constraint evaluates the score by checking the max used capacity key out of all the capacity
 * keys.
 * The higher the maximum usage value for the capacity key, the lower the score will be, implying
 * that it is that much less desirable to assign anything on the given node.
 * It is a greedy approach since it evaluates only on the most used capacity key.
 */
class MaxCapacityUsageInstanceConstraint extends UsageSoftConstraint {

  @Override
  protected double getAssignmentScore(AssignableNode node, AssignableReplica replica,
      ClusterContext clusterContext) {
    float estimatedMaxUtilization = clusterContext.getEstimatedMaxUtilization();
    float projectedHighestUtilization = node.getProjectedHighestUtilization(replica.getCapacity());
    return computeUtilizationScore(estimatedMaxUtilization, projectedHighestUtilization);
  }
}