helix-core/src/main/java/org/apache/helix/controller/changedetector/ChangeDetector.java

package org.apache.helix.controller.changedetector;

/*
 * 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 java.util.Collection;
import org.apache.helix.HelixConstants;

/**
 * ChangeDetector interface that will be used to track deltas in the cluster from one pipeline run
 * to another. The interface methods are designed to be flexible for both the resource pipeline and
 * the task pipeline.
 * TODO: Consider splitting this up into two different ChangeDetector interfaces:
 * TODO: PropertyBasedChangeDetector and PathBasedChangeDetector.
 */
public interface ChangeDetector {

  /**
   * Returns all types of changes detected.
   * @return a collection of ChangeTypes
   */
  Collection<HelixConstants.ChangeType> getChangeTypes();

  /**
   * Returns the names of items that changed based on the change type given.
   * @return a collection of names of items that changed
   */
  Collection<String> getChangesByType(HelixConstants.ChangeType changeType);

  /**
   * Returns the names of items that were added based on the change type given.
   * @return a collection of names of items that were added
   */
  Collection<String> getAdditionsByType(HelixConstants.ChangeType changeType);

  /**
   * Returns the names of items that were removed based on the change type given.
   * @return a collection of names of items that were removed
   */
  Collection<String> getRemovalsByType(HelixConstants.ChangeType changeType);
}