murblanc commented on a change in pull request #1684: URL: https://github.com/apache/lucene-solr/pull/1684#discussion_r468412029
########## File path: solr/core/src/java/org/apache/solr/cluster/placement/plugins/SamplePluginMinimizeCores.java ########## @@ -0,0 +1,132 @@ +/* + * 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.plugins; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.Comparator; +import java.util.HashSet; +import java.util.Iterator; +import java.util.Set; +import java.util.Map; + +import com.google.common.collect.Ordering; +import com.google.common.collect.TreeMultimap; +import org.apache.solr.cluster.placement.Cluster; +import org.apache.solr.cluster.placement.CoresCountPropertyValue; +import org.apache.solr.cluster.placement.CreateNewCollectionPlacementRequest; +import org.apache.solr.cluster.placement.Node; +import org.apache.solr.cluster.placement.PlacementException; +import org.apache.solr.cluster.placement.PlacementPlugin; +import org.apache.solr.cluster.placement.PropertyKey; +import org.apache.solr.cluster.placement.PropertyKeyFactory; +import org.apache.solr.cluster.placement.PropertyValue; +import org.apache.solr.cluster.placement.PropertyValueFetcher; +import org.apache.solr.cluster.placement.Replica; +import org.apache.solr.cluster.placement.ReplicaPlacement; +import org.apache.solr.cluster.placement.PlacementRequest; +import org.apache.solr.cluster.placement.PlacementPlan; +import org.apache.solr.cluster.placement.PlacementPlanFactory; +import org.apache.solr.common.util.SuppressForbidden; + +/** + * Implements placing replicas to minimize number of cores per {@link Node}, while not placing two replicas of the same + * shard on the same node. + * + * TODO: code not tested and never run, there are no implementation yet for used interfaces + */ +public class SamplePluginMinimizeCores implements PlacementPlugin { + + @SuppressForbidden(reason = "Ordering.arbitrary() has no equivalent in Comparator class. Rather reuse than copy.") + public PlacementPlan computePlacement(Cluster cluster, PlacementRequest placementRequest, PropertyKeyFactory propertyFactory, + PropertyValueFetcher propertyFetcher, PlacementPlanFactory placementPlanFactory) throws PlacementException { + // This plugin only supports Creating a collection. + if (!(placementRequest instanceof CreateNewCollectionPlacementRequest)) { + throw new PlacementException("This toy plugin only supports creating collections"); + } + + final CreateNewCollectionPlacementRequest reqCreateCollection = (CreateNewCollectionPlacementRequest) placementRequest; + + final int totalReplicasPerShard = reqCreateCollection.getNrtReplicationFactor() + + reqCreateCollection.getTlogReplicationFactor() + reqCreateCollection.getPullReplicationFactor(); + + if (cluster.getLiveNodes().size() < totalReplicasPerShard) { + throw new PlacementException("Cluster size too small for number of replicas per shard"); + } + + // Get number of cores on each Node + TreeMultimap<Integer, Node> nodesByCores = TreeMultimap.create(Comparator.naturalOrder(), Ordering.arbitrary()); Review comment: Strong typing was one requirement (and strong typing is not only return type, it's also nice names for methods to access these values), the other one was efficiency: being able to fetch ALL needed properties from a remote Node at once (i.e. not requesting metrics first and system properties second which would force the Solr side framework to do two round trips - caching and optimizations aside). That's why we have the notion of property key, to be able to "accumulate" the properties to fetch, then we have asingle interface per property, allowing clean access to the value (for cores it's the call coresCountPropertyValue.getCoresCount() line 85 below). The "complexity" of the structure here is the plug-in implementation, not the API, using sorted data structures to compute a placement quickly. This should be compared (in complexity) to the previous approach of generating all possible placements and comparing them. ---------------------------------------------------------------- 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. 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