kfaraz commented on code in PR #13197: URL: https://github.com/apache/druid/pull/13197#discussion_r994062342
########## server/src/main/java/org/apache/druid/server/coordinator/SegmentLoader.java: ########## @@ -0,0 +1,472 @@ +/* + * 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.druid.server.coordinator; + +import com.google.common.collect.Sets; +import org.apache.druid.java.util.emitter.EmittingLogger; +import org.apache.druid.timeline.DataSegment; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.EnumMap; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Set; +import java.util.TreeSet; +import java.util.stream.Collectors; + +/** + * Used by the coordinator in each run for segment loading, dropping, balancing + * and broadcasting. + * <p> + * An instance of this class is freshly created for each coordinator run. + */ +public class SegmentLoader +{ + private static final EmittingLogger log = new EmittingLogger(SegmentLoader.class); + + private final SegmentStateManager stateManager; + private final DruidCluster cluster; + private final CoordinatorStats stats = new CoordinatorStats(); + private final SegmentReplicantLookup replicantLookup; + private final BalancerStrategy strategy; + private final int maxLoadQueueSize; + + public SegmentLoader(SegmentStateManager stateManager, DruidCoordinatorRuntimeParams runParams) + { + this.stateManager = stateManager; + this.strategy = runParams.getBalancerStrategy(); + this.cluster = runParams.getDruidCluster(); + this.replicantLookup = runParams.getSegmentReplicantLookup(); + this.maxLoadQueueSize = runParams.getCoordinatorDynamicConfig() + .getMaxSegmentsInNodeLoadingQueue(); + } + + public CoordinatorStats getStats() + { + return stats; + } + + /** + * Moves the given segment between two servers of the same tier. + * <p> + * See if we can move balancing here. + */ + public boolean moveSegment(DataSegment segment, ServerHolder fromServer, ServerHolder toServer) + { + if (!fromServer.getServer().getTier().equals(toServer.getServer().getTier())) { + return false; + } + + // fromServer must be loading or serving the segment + // and toServer must be able to load it + final SegmentState stateOnSrc = fromServer.getSegmentState(segment); + if ((stateOnSrc != SegmentState.LOADING && stateOnSrc != SegmentState.LOADED) + || !canLoadSegment(toServer, segment)) { + return false; + } + + final boolean cancelSuccess = stateOnSrc == SegmentState.LOADING + && stateManager.cancelOperation(SegmentState.LOADING, segment, fromServer); + + if (cancelSuccess) { + int loadedCountOnTier = replicantLookup + .getLoadedReplicants(segment.getId(), toServer.getServer().getTier()); + stateManager.loadSegment(segment, toServer, loadedCountOnTier < 1); + } else { + return stateManager.moveSegment(segment, fromServer, toServer); + } + + return true; + } + + /** + * Queues load or drop of replicas of the given segment to achieve the + * target replication level in all the tiers. + */ + public void updateReplicas(DataSegment segment, Map<String, Integer> tierToReplicaCount) + { + // Handle every target tier + tierToReplicaCount.forEach((tier, numReplicas) -> { + updateReplicasOnTier(segment, tier, tierToReplicaCount.get(tier)); + stats.addToTieredStat(CoordinatorStats.REQUIRED_CAPACITY, tier, segment.getSize() * numReplicas); + }); + + // Find the minimum number of segments required for fault tolerance + final int totalTargetReplicas = tierToReplicaCount.values().stream() + .reduce(0, Integer::sum); + final int minLoadedSegments = totalTargetReplicas > 1 ? 2 : 1; + + // Drop segment from unneeded tiers if requirement is met across target tiers + int loadedTargetReplicas = 0; + final Set<String> targetTiers = tierToReplicaCount.keySet(); + for (String tier : targetTiers) { + loadedTargetReplicas += replicantLookup.getLoadedReplicants(segment.getId(), tier); + } + if (loadedTargetReplicas < minLoadedSegments) { + return; + } + + final Set<String> dropTiers = Sets.newHashSet(cluster.getTierNames()); + dropTiers.removeAll(targetTiers); + for (String dropTier : dropTiers) { + updateReplicasOnTier(segment, dropTier, 0); + } + } + + /** + * Broadcasts the given segment to all servers that are broadcast targets and + * queues a drop of the segment from decommissioning servers. + */ + public void broadcastSegment(DataSegment segment) + { + int assignedCount = 0; + int droppedCount = 0; + for (ServerHolder server : cluster.getAllServers()) { + // Ignore servers which are not broadcast targets + if (!server.getServer().getType().isSegmentBroadcastTarget()) { + continue; + } + + if (server.isDecommissioning()) { + droppedCount += dropBroadcastSegment(segment, server) ? 1 : 0; + } else { + assignedCount += loadBroadcastSegment(segment, server) ? 1 : 0; + } + } + + if (assignedCount > 0) { + stats.addToDataSourceStat(CoordinatorStats.BROADCAST_LOADS, segment.getDataSource(), assignedCount); + } + if (droppedCount > 0) { + stats.addToDataSourceStat(CoordinatorStats.BROADCAST_DROPS, segment.getDataSource(), droppedCount); + } + } + + /** + * Marks the given segment as unused. + */ + public void deleteSegment(DataSegment segment) + { + stateManager.deleteSegment(segment); + stats.addToGlobalStat(CoordinatorStats.DELETED_SEGMENTS, 1); + } + + /** + * Checks if the server can load the given segment. + * <p> + * A load is possible only if the server meets all of the following criteria: + * <ul> + * <li>is not already serving or loading the segment</li> + * <li>is not being decommissioned</li> + * <li>has not already exceeded the load queue limit in this run</li> + * <li>has available disk space</li> + * </ul> + */ + public boolean canLoadSegment(ServerHolder server, DataSegment segment) + { + return server.canLoadSegment(segment) + && (maxLoadQueueSize == 0 || maxLoadQueueSize > server.getSegmentsQueuedForLoad()); + } + + /** + * Loads the broadcast segment if it is not loaded on the given server. + * Returns true only if the segment was successfully queued for load on the server. + */ + private boolean loadBroadcastSegment(DataSegment segment, ServerHolder server) + { + final SegmentState state = server.getSegmentState(segment); + if (state == SegmentState.LOADED || state == SegmentState.LOADING) { + return false; + } + + // Cancel drop if it is in progress + boolean dropCancelled = stateManager.cancelOperation(SegmentState.DROPPING, segment, server); + if (dropCancelled) { + return false; + } + + if (canLoadSegment(server, segment) + && stateManager.loadSegment(segment, server, true)) { + return true; + } else { + log.makeAlert("Failed to broadcast segment for [%s]", segment.getDataSource()) Review Comment: Yes, I am going through all the log messages to make sure they are less ambiguous. -- This is an automated message from the Apache Git Service. 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