narendly commented on a change in pull request #392: Implement Cluster Model Provider. URL: https://github.com/apache/helix/pull/392#discussion_r314149434
########## File path: helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/model/ClusterModelProvider.java ########## @@ -0,0 +1,247 @@ +package org.apache.helix.controller.rebalancer.waged.model; + +/* + * 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 org.apache.helix.HelixException; +import org.apache.helix.controller.dataproviders.ResourceControllerDataProvider; +import org.apache.helix.controller.rebalancer.waged.ClusterDataDetector; +import org.apache.helix.model.ClusterConfig; +import org.apache.helix.model.IdealState; +import org.apache.helix.model.InstanceConfig; +import org.apache.helix.model.Resource; +import org.apache.helix.model.ResourceAssignment; +import org.apache.helix.model.ResourceConfig; +import org.apache.helix.model.StateModelDefinition; + +import java.util.Collections; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Optional; +import java.util.Set; +import java.util.stream.Collectors; + +/** + * This util class generates Cluster Model object based on the controller's data cache. + */ +public class ClusterModelProvider { + + /** + * @param dataProvider The controller's data cache. + * @param resourceMap The full list of the resources to be rebalanced. Note that any + * resources that are not in this list will be removed from the + * final assignment. + * @param activeInstances The active instances that will be used in the calculation. + * Note this list can be different from the real active node list + * according to the rebalancer logic. + * @param clusterChanges All the cluster changes that happened after the previous rebalance. + * @param baselineAssignment The persisted Baseline assignment. + * @param bestPossibleAssignment The persisted Best Possible assignment that was generated in the + * previous rebalance. + * @return Generate a new Cluster Model object according to the current cluster status. + */ + public static ClusterModel generateClusterModel(ResourceControllerDataProvider dataProvider, + Map<String, Resource> resourceMap, Set<String> activeInstances, + Map<ClusterDataDetector.ChangeType, Set<String>> clusterChanges, + Map<String, ResourceAssignment> baselineAssignment, + Map<String, ResourceAssignment> bestPossibleAssignment) { + // Generate replica objects for all the resource partitions. + // <resource, replica set> + Map<String, Set<AssignableReplica>> replicaMap = + parseAllReplicas(dataProvider, resourceMap, activeInstances.size()); + + // Check if the replicas need to be reassigned. + Map<String, Set<AssignableReplica>> allocatedReplicas = + new HashMap<>(); // <instanceName, replica set> + Set<AssignableReplica> toBeAssignedReplicas = + findToBeAssignedReplicas(replicaMap, clusterChanges, activeInstances, + bestPossibleAssignment, allocatedReplicas); + + // Construct all the assignable nodes and initialize with the allocated replicas. + Set<AssignableNode> assignableNodes = + parseAllNodes(dataProvider.getClusterConfig(), dataProvider.getInstanceConfigMap(), + activeInstances, allocatedReplicas); + + // Construct and initialize cluster context. + ClusterContext context = new ClusterContext( + replicaMap.values().stream().flatMap(Set::stream).collect(Collectors.toSet()), + activeInstances.size()); + // Initial the cluster context with the allocated assignments. + context.setAssignmentForFaultZoneMap(mapAssignmentToFaultZone(assignableNodes)); + + return new ClusterModel(context, toBeAssignedReplicas, assignableNodes, baselineAssignment, + bestPossibleAssignment); + } + + /** + * Find the minimum set of replicas that need to be reassigned. + * A replica needs to be reassigned if one of the following condition is true: + * 1. Cluster topology (the cluster config / any instance config) has been updated. + * 2. The baseline assignment has been updated. + * 3. The resource config has been updated. + * 4. The resource idealstate has been updated. TODO remove this condition when all resource configurations are migrated to resource config. + * 5. If the current best possible assignment does not contain the partition's valid assignment. + * + * @param replicaMap A map contains all the replicas grouped by resource name. + * @param clusterChanges A map contains all the important metadata updates that happened after the previous rebalance. + * @param activeInstances All the instances that are alive and enabled. + * @param bestPossibleAssignment The current best possible assignment. + * @param allocatedReplicas Return the allocated replicas grouped by the target instance name. + * @return The replicas that need to be reassigned. + */ + private static Set<AssignableReplica> findToBeAssignedReplicas( Review comment: Can we change the method name? It is very confusing. Use findReplicasNeedingReassignment or something is better. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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