aho135 commented on code in PR #19094: URL: https://github.com/apache/druid/pull/19094#discussion_r2908695095
########## server/src/main/java/org/apache/druid/client/selector/PooledTierSelectorStrategy.java: ########## @@ -0,0 +1,158 @@ +/* + * 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.client.selector; + +import com.fasterxml.jackson.annotation.JacksonInject; +import com.fasterxml.jackson.annotation.JsonCreator; +import it.unimi.dsi.fastutil.ints.Int2ObjectMap; +import it.unimi.dsi.fastutil.ints.Int2ObjectRBTreeMap; +import org.apache.druid.client.QueryableDruidServer; +import org.apache.druid.java.util.emitter.EmittingLogger; +import org.apache.druid.java.util.emitter.service.ServiceEmitter; +import org.apache.druid.java.util.emitter.service.ServiceMetricEvent; +import org.apache.druid.query.Query; +import org.apache.druid.query.metadata.metadata.SegmentMetadataQuery; +import org.apache.druid.timeline.DataSegment; + +import javax.annotation.Nullable; +import java.util.Comparator; +import java.util.LinkedHashSet; +import java.util.List; +import java.util.Set; + +/** + * A {@link TierSelectorStrategy} that pools servers with the configured set of priorities from {@link PooledTierSelectorStrategyConfig#getPriorities()} + * and delegates server selection to the configured {@link ServerSelectorStrategy}. + * <p> + * Unlike other {@link TierSelectorStrategy} like {@link CustomTierSelectorStrategy} + * which has a preference for priority order, this strategy treats all configured priorities equally + * by combining their servers into a single selection pool and delegates to {@link ServerSelectorStrategy} to do + * the server selection. If no servers match the configured priorities in the pool, an empty server list is returned, + * which may cause queries to return partial or no data. + * <p> + * Example configuration: + * <li> <code> druid.broker.select.tier=pooled </code> </li> + * <li> <code> druid.broker.select.tier.pooled.priorities=[2,1] </code> </li> + * <p> + * With this configuration, servers with priority 2 and 1 are pooled together and + * selection is delegated to the {@link ServerSelectorStrategy}. Servers with other + * priorities are ignored. + */ +public class PooledTierSelectorStrategy extends AbstractTierSelectorStrategy +{ + private static final EmittingLogger log = new EmittingLogger(PooledTierSelectorStrategy.class); + public static final String TYPE = "pooled"; + + private final ServerSelectorStrategy serverSelectorStrategy; + private final PooledTierSelectorStrategyConfig config; + private final ServiceEmitter emitter; + private final Set<Integer> configuredPriorities; + + @JsonCreator + public PooledTierSelectorStrategy( + @JacksonInject final ServerSelectorStrategy serverSelectorStrategy, + @JacksonInject final PooledTierSelectorStrategyConfig config, + @JacksonInject final ServiceEmitter emitter + ) + { + super(serverSelectorStrategy); + this.serverSelectorStrategy = serverSelectorStrategy; + this.config = config; + this.emitter = emitter; + this.configuredPriorities = config.getPriorities(); + } + + @Override + public <T> List<QueryableDruidServer> pick( + @Nullable final Query<T> query, + final Int2ObjectRBTreeMap<Set<QueryableDruidServer>> prioritizedServers, + final DataSegment segment, + final int numServersToPick + ) + { + final Set<QueryableDruidServer> candidateServerPool = new LinkedHashSet<>(); + + for (Int2ObjectMap.Entry<Set<QueryableDruidServer>> entry : prioritizedServers.int2ObjectEntrySet()) { + final int priority = entry.getIntKey(); + final Set<QueryableDruidServer> servers = entry.getValue(); + + if (configuredPriorities.contains(priority)) { + candidateServerPool.addAll(servers); + } else { + log.debug( + "Server priority[%d] not in the configured list of priorities[%s] so ignore servers[%s] for query[%s]", + priority, config.getPriorities(), servers, query + ); + } + } + + if (candidateServerPool.isEmpty()) { + if (query == null || query instanceof SegmentMetadataQuery) { + // Debug logging to reduce logging spam as these are typically system-generated segment metadata queries + log.debug( + "No server found for query[%s] from server priorities[%s]. Configured priorities[%s].", + query, prioritizedServers.keySet(), config.getPriorities() + ); + } else { + log.warn( + "No servers found for query[%s] matching configured priorities[%s]. Available priorities[%s].", + query, config.getPriorities(), prioritizedServers.keySet() + ); + emitter.emit( + ServiceMetricEvent.builder() + .setMetric("tierSelector/noServer", 1) + .setDimension("dataSource", String.valueOf(query.getDataSource())) + .setDimension("tierSelectorType", TYPE) + .setDimension("queryType", query.getType()) + .setDimension("queryPriority", String.valueOf(query.context().getPriority())) + .setDimensionIfNotNull("queryId", query.getId()) + ); + } + return List.of(); + } + + final List<QueryableDruidServer> selectedServers = serverSelectorStrategy.pick(query, candidateServerPool, segment, numServersToPick); + log.debug("Selected servers[%s] for query[%s] from given servers[%s] and candidateServerPool[%s]", selectedServers, query, prioritizedServers, candidateServerPool); + return selectedServers; + } + + /** + * @return the natural order of priorities since priority order doesn't matter for this strategy as the configured set of + * priorities in the pool are treated equally and delegated ot {@link #serverSelectorStrategy}. Review Comment: ```suggestion * priorities in the pool are treated equally and delegated to {@link #serverSelectorStrategy}. ``` -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
