solr/core/src/java/org/apache/solr/cluster/placement/PlacementPlan.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.solr.cluster.placement;

import org.apache.solr.cluster.Node;

import java.util.Set;

/**
 * A fully specified plan or instructions for placement, deletion or move to be applied to the cluster.<p>
 * Fully specified means the actual {@link Node}'s on which to place replicas have been decided.
 * <p>
 * Instances are created by plugin code using {@link PlacementPlanFactory}. This interface obviously doesn't expose much but
 * the underlying Solr side implementation has all that is needed (and will do at least one cast in order to execute the
 * plan, likely then using some type of visitor pattern).
 */
public interface PlacementPlan {
  /**
   * @return the {@link PlacementRequest} at the origin of this {@link PlacementPlan}, as passed to the {@link PlacementPlanFactory} method
   * that created this instance.
   */
  PlacementRequest getRequest();

  /**
   * @return the set of {@link ReplicaPlacement}'s computed by the plugin to implement the request
   */
  Set<ReplicaPlacement> getReplicaPlacements();
}