| package org.apache.helix.cloud.topology; |
| |
| /* |
| * 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 com.google.common.base.Preconditions; |
| import com.google.common.collect.ImmutableMap; |
| import java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| import org.apache.helix.cloud.constants.VirtualTopologyGroupConstants; |
| import org.apache.helix.util.HelixUtil; |
| |
| |
| /** |
| * A strategy that densely assign virtual groups with input instance list, it doesn't move to the next one until |
| * the current one is filled. |
| * Given that instances.size = instancesPerGroup * numGroups + residuals, |
| * we break [residuals] into the first few groups, as a result each virtual group will have |
| * either [instancesPerGroup] or [instancesPerGroup + 1] instances. |
| */ |
| public class FifoVirtualGroupAssignmentAlgorithm implements VirtualGroupAssignmentAlgorithm { |
| private static final FifoVirtualGroupAssignmentAlgorithm _instance = new FifoVirtualGroupAssignmentAlgorithm(); |
| |
| private FifoVirtualGroupAssignmentAlgorithm() { } |
| |
| public static FifoVirtualGroupAssignmentAlgorithm getInstance() { |
| return _instance; |
| } |
| |
| @Override |
| public Map<String, Set<String>> computeAssignment(int numGroups, String virtualGroupName, |
| Map<String, Set<String>> zoneMapping) { |
| List<String> sortedInstances = HelixUtil.sortAndFlattenZoneMapping(zoneMapping); |
| Map<String, Set<String>> assignment = new HashMap<>(); |
| // #instances = instancesPerGroupBase * numGroups + residuals |
| int instancesPerGroupBase = sortedInstances.size() / numGroups; |
| int residuals = sortedInstances.size() % numGroups; // assign across the first #residuals groups |
| List<Integer> numInstances = new ArrayList<>(); |
| int instanceInd = 0; |
| for (int groupInd = 0; groupInd < numGroups; groupInd++) { |
| int num = groupInd < residuals |
| ? instancesPerGroupBase + 1 |
| : instancesPerGroupBase; |
| String groupId = computeVirtualGroupId(groupInd, virtualGroupName); |
| assignment.put(groupId, new HashSet<>()); |
| for (int i = 0; i < num; i++) { |
| assignment.get(groupId).add(sortedInstances.get(instanceInd)); |
| instanceInd++; |
| } |
| numInstances.add(num); |
| } |
| Preconditions.checkState(numInstances.stream().mapToInt(Integer::intValue).sum() == sortedInstances.size()); |
| return ImmutableMap.copyOf(assignment); |
| } |
| |
| private static String computeVirtualGroupId(int groupIndex, String virtualGroupName) { |
| return virtualGroupName + VirtualTopologyGroupConstants.GROUP_NAME_SPLITTER + groupIndex; |
| } |
| } |