i3wangyi commented on a change in pull request #388: Add ChangeDetector interface and ResourceChangeDetector implementation URL: https://github.com/apache/helix/pull/388#discussion_r313594282
########## File path: helix-core/src/main/java/org/apache/helix/controller/changedetector/ResourceChangeDetector.java ########## @@ -0,0 +1,164 @@ +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 java.util.Collections; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import org.apache.helix.HelixConstants; +import org.apache.helix.HelixException; +import org.apache.helix.HelixProperty; +import org.apache.helix.controller.dataproviders.ResourceControllerDataProvider; + +/** + * ResourceChangeDetector implements ChangeDetector. It caches resource-related metadata from + * Helix's main resource pipeline cache (DataProvider) and the computation results of change + * detection. + * WARNING: the methods of this class are not thread-safe. + */ +public class ResourceChangeDetector implements ChangeDetector { + + private ResourceChangeCache _oldCache; // cache snapshot for previous pipeline run + private ResourceChangeCache _newCache; // cache snapshot for this pipeline run + + private Map<String, ? extends HelixProperty> _oldPropertyMap; + private Map<String, ? extends HelixProperty> _newPropertyMap; + + // The following caches the computation results + private Map<HelixConstants.ChangeType, Collection<String>> _changedItems = new HashMap<>(); + private Map<HelixConstants.ChangeType, Collection<String>> _addedItems = new HashMap<>(); + private Map<HelixConstants.ChangeType, Collection<String>> _removedItems = new HashMap<>(); + + /** + * Compare the underlying HelixProperty objects and produce a collection of names of changed + * properties. + * @return + */ + private Collection<String> getChangedItems() { + Collection<String> changedItems = new HashSet<>(); + _oldPropertyMap.forEach((name, property) -> { + if (_newPropertyMap.containsKey(name) && !property.equals(_newPropertyMap.get(name))) { + changedItems.add(name); + } + }); + return changedItems; + } + + /** + * Return a collection of names that are newly added. + * @return + */ + private Collection<String> getAddedItems() { Review comment: For 2 set difference operation (A - B), I would prefer Guava's library, which is more clear. https://www.geeksforgeeks.org/sets-difference-function-guava-java/ ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@helix.apache.org For additional commands, e-mail: reviews-h...@helix.apache.org
