Jackie-Jiang commented on a change in pull request #4269: Add interface and implementations for the new segment assignment URL: https://github.com/apache/incubator-pinot/pull/4269#discussion_r290441378
########## File path: pinot-controller/src/main/java/org/apache/pinot/controller/helix/core/assignment/segment/BalanceNumSegmentAssignmentStrategy.java ########## @@ -0,0 +1,121 @@ +/** + * 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.pinot.controller.helix.core.assignment.segment; + +import com.google.common.base.Preconditions; +import java.util.ArrayList; +import java.util.LinkedHashMap; +import java.util.List; +import java.util.Map; +import java.util.PriorityQueue; +import java.util.TreeMap; +import org.apache.helix.ZNRecord; +import org.apache.helix.controller.rebalancer.strategy.AutoRebalanceStrategy; +import org.apache.helix.store.zk.ZkHelixPropertyStore; +import org.apache.pinot.common.config.TableConfig; +import org.apache.pinot.common.utils.CommonConstants.Helix.StateModel.SegmentOnlineOfflineStateModel; +import org.apache.pinot.common.utils.Pairs; +import org.apache.pinot.controller.helix.core.assignment.InstancePartitions; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + + +/** + * Segment assignment strategy that assigns segment to the instance with the least number of segments. In case of a tie, + * assigns to the instance with the smallest index in the list. The strategy ensures that replicas of the same segment + * are not assigned to the same server. + * <p>To rebalance a table, use Helix AutoRebalanceStrategy. + */ +public class BalanceNumSegmentAssignmentStrategy implements SegmentAssignmentStrategy { + private static final Logger LOGGER = LoggerFactory.getLogger(BalanceNumSegmentAssignmentStrategy.class); + + private String _tableNameWithType; + private int _replication; + + @Override + public void init(ZkHelixPropertyStore<ZNRecord> propertyStore, TableConfig tableConfig) { + _tableNameWithType = tableConfig.getTableName(); + _replication = tableConfig.getValidationConfig().getReplicationNumber(); + + LOGGER + .info("Initialized BalanceNumSegmentAssignmentStrategy for table: {} with replication: {}", _tableNameWithType, + _replication); + } + + @Override + public List<String> assignSegment(String segmentName, Map<String, Map<String, String>> currentAssignment, + InstancePartitions instancePartitions) { + List<String> instances = getInstances(instancePartitions); + int[] numSegmentsAssigned = SegmentAssignmentUtils.getNumSegmentsAssigned(currentAssignment, instances); + + // Assign the segment to the instance with the least segments, or the smallest id if there is a tie + int numInstances = numSegmentsAssigned.length; + PriorityQueue<Pairs.IntPair> heap = new PriorityQueue<>(numInstances, Pairs.intPairComparator()); + for (int instanceId = 0; instanceId < numInstances; instanceId++) { + heap.add(new Pairs.IntPair(numSegmentsAssigned[instanceId], instanceId)); + } + List<String> instancesAssigned = new ArrayList<>(_replication); + for (int i = 0; i < _replication; i++) { + instancesAssigned.add(instances.get(heap.remove().getRight())); + } + + LOGGER.info("Assigned segment: {} to instances: {} for table: {}", segmentName, instancesAssigned, + _tableNameWithType); + return instancesAssigned; + } + + @Override + public Map<String, Map<String, String>> rebalanceTable(Map<String, Map<String, String>> currentAssignment, + InstancePartitions instancePartitions) { + List<String> instances = getInstances(instancePartitions); + + // Use Helix AutoRebalanceStrategy to rebalance the table + LinkedHashMap<String, Integer> states = new LinkedHashMap<>(); + states.put(SegmentOnlineOfflineStateModel.ONLINE, _replication); + AutoRebalanceStrategy autoRebalanceStrategy = + new AutoRebalanceStrategy(_tableNameWithType, new ArrayList<>(currentAssignment.keySet()), states); + // Make a copy of the current assignment because this step might change the passed in assignment + Map<String, Map<String, String>> currentAssignmentCopy = new TreeMap<>(); + for (Map.Entry<String, Map<String, String>> entry : currentAssignment.entrySet()) { + String segmentName = entry.getKey(); + Map<String, String> instanceStateMap = entry.getValue(); + currentAssignmentCopy.put(segmentName, new TreeMap<>(instanceStateMap)); + } + Map<String, Map<String, String>> newAssignment = + autoRebalanceStrategy.computePartitionAssignment(instances, instances, currentAssignmentCopy, null) + .getMapFields(); + + LOGGER.info( + "Rebalanced {} segments with {} replicas to instances: {} for table: {}, number of segments to be moved to each instance: {}", + currentAssignment.size(), _replication, instances, _tableNameWithType, + SegmentAssignmentUtils.getNumSegmentsToBeMoved(currentAssignment, newAssignment)); + return newAssignment; + } + + private List<String> getInstances(InstancePartitions instancePartitions) { + Preconditions.checkArgument(instancePartitions.getNumPartitions() == 1, + "The instance partitions should contain only 1 partition"); + Preconditions.checkArgument(instancePartitions.getNumReplicas() == 1, + "The instance partitions should contain only 1 replica"); + List<String> instances = instancePartitions.getInstances(0, 0); + Preconditions.checkState(instances.size() >= _replication, Review comment: That will be handled in the instance assignment step (in the upcoming pr). This check is for cases where people modify table replication without re-calculate instance partitions. ---------------------------------------------------------------- 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: commits-unsubscr...@pinot.apache.org For additional commands, e-mail: commits-h...@pinot.apache.org
