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Apache Solr (module: core)
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/*
 * 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.solr.cluster.placement.impl;

import java.util.Set;
import org.apache.solr.cloud.api.collections.Assign;
import org.apache.solr.cluster.Cluster;
import org.apache.solr.cluster.Node;
import org.apache.solr.cluster.SolrCollection;
import org.apache.solr.cluster.placement.BalanceRequest;

public class BalanceRequestImpl implements BalanceRequest {

  private final SolrCollection solrCollection;
  private final Set nodes;
  private final int maximumBalanceSkew;

  public BalanceRequestImpl(Set nodes) {
    this(nodes, -1);
  }

  public BalanceRequestImpl(Set nodes, int maximumBalanceSkew) {
    this.nodes = nodes;
    this.maximumBalanceSkew = maximumBalanceSkew;
    this.solrCollection = null;
  }

  @Override
  public Set getNodes() {
    return nodes;
  }

  @Override
  public int getMaximumBalanceSkew() {
    return maximumBalanceSkew;
  }

  @Override
  public SolrCollection getCollection() {
    return solrCollection;
  }

  /** Returns a {@link BalanceRequest} that can be consumed by a plugin to balance replicas */
  static BalanceRequestImpl create(Cluster cluster, Set nodeNames, int maximumBalanceSkew)
      throws Assign.AssignmentException {
    final Set nodes;
    // If no nodes specified, use all live data nodes. If nodes are specified, use specified list.
    if (nodeNames != null && !nodeNames.isEmpty()) {
      if (nodeNames.size() == 1) {
        throw new Assign.AssignmentException(
            "Bad balance request: cannot balance across a single node: "
                + nodeNames.stream().findAny().get());
      }
      nodes = SimpleClusterAbstractionsImpl.NodeImpl.getNodes(nodeNames);

      for (Node n : nodes) {
        if (!cluster.getLiveDataNodes().contains(n)) {
          throw new Assign.AssignmentException(
              "Bad balance request: specified node is a non-data hosting node:" + n.getName());
        }
      }
    } else {
      nodes = cluster.getLiveDataNodes();
      if (nodes.isEmpty()) {
        throw new Assign.AssignmentException("Impossible balance request: no live data nodes");
      }
    }

    return new BalanceRequestImpl(nodes, maximumBalanceSkew);
  }
}