adarshsanjeev commented on code in PR #15024: URL: https://github.com/apache/druid/pull/15024#discussion_r1349549352
########## extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/LoadedSegmentDataProvider.java: ########## @@ -0,0 +1,234 @@ +/* + * 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.msq.exec; + +import com.fasterxml.jackson.databind.JavaType; +import com.fasterxml.jackson.databind.ObjectMapper; +import com.google.common.annotations.VisibleForTesting; +import com.google.common.base.Throwables; +import com.google.common.collect.ImmutableList; +import org.apache.druid.client.coordinator.CoordinatorClient; +import org.apache.druid.common.guava.FutureUtils; +import org.apache.druid.discovery.DataServerClient; +import org.apache.druid.java.util.common.IOE; +import org.apache.druid.java.util.common.Pair; +import org.apache.druid.java.util.common.RetryUtils; +import org.apache.druid.java.util.common.guava.Sequence; +import org.apache.druid.java.util.common.guava.Yielder; +import org.apache.druid.java.util.common.guava.Yielders; +import org.apache.druid.java.util.common.io.Closer; +import org.apache.druid.java.util.common.logger.Logger; +import org.apache.druid.msq.counters.ChannelCounters; +import org.apache.druid.msq.input.table.RichSegmentDescriptor; +import org.apache.druid.query.Queries; +import org.apache.druid.query.Query; +import org.apache.druid.query.QueryInterruptedException; +import org.apache.druid.query.QueryToolChest; +import org.apache.druid.query.QueryToolChestWarehouse; +import org.apache.druid.query.SegmentDescriptor; +import org.apache.druid.query.TableDataSource; +import org.apache.druid.query.aggregation.MetricManipulatorFns; +import org.apache.druid.query.context.DefaultResponseContext; +import org.apache.druid.query.context.ResponseContext; +import org.apache.druid.rpc.FixedSetServiceLocator; +import org.apache.druid.rpc.RpcException; +import org.apache.druid.rpc.ServiceClientFactory; +import org.apache.druid.server.coordination.DruidServerMetadata; + +import java.io.IOException; +import java.util.List; +import java.util.Set; +import java.util.function.Function; + +/** + * Class responsible for querying dataservers and retriving results for a given query. Also queries the coordinator + * to check if a segment has been handed off. + */ +public class LoadedSegmentDataProvider +{ + private static final Logger log = new Logger(LoadedSegmentDataProvider.class); + private static final int DEFAULT_NUM_TRIES = 5; + private final String dataSource; + private final ChannelCounters channelCounters; + private final ServiceClientFactory serviceClientFactory; + private final CoordinatorClient coordinatorClient; + private final ObjectMapper objectMapper; + private final QueryToolChestWarehouse warehouse; + + public LoadedSegmentDataProvider( + String dataSource, + ChannelCounters channelCounters, + ServiceClientFactory serviceClientFactory, + CoordinatorClient coordinatorClient, + ObjectMapper objectMapper, + QueryToolChestWarehouse warehouse + ) + { + this.dataSource = dataSource; + this.channelCounters = channelCounters; + this.serviceClientFactory = serviceClientFactory; + this.coordinatorClient = coordinatorClient; + this.objectMapper = objectMapper; + this.warehouse = warehouse; + } + + @VisibleForTesting + DataServerClient makeDataServerClient(FixedSetServiceLocator serviceLocator) + { + return new DataServerClient(serviceClientFactory, serviceLocator, objectMapper); + } + + /** + * Queries a data server and returns a {@link Yielder} for the results, retrying if needed. If a dataserver indicates + * that the segment was not found, checks with the coordinator to see if the segment was handed off. + * - If the segment was handed off, returns with a {@link DataServerQueryStatus#HANDOFF} status. + * - If the segment was not handed off, retries with the known list of servers and throws an exception if the retry + * count is exceeded. + * + * @param <QueryType> result return type for the query from the data server + * @param <RowType> type of the result rows after parsing from QueryType object + */ + public <RowType, QueryType> Pair<DataServerQueryStatus, Yielder<RowType>> fetchRowsFromDataServer( + Query<QueryType> query, + RichSegmentDescriptor segmentDescriptor, + Function<Sequence<QueryType>, Sequence<RowType>> mappingFunction, + Closer closer + ) throws IOException + { + final Query<QueryType> preparedQuery = Queries.withSpecificSegments( + query.withDataSource(new TableDataSource(dataSource)), + ImmutableList.of(segmentDescriptor) + ); + + Set<DruidServerMetadata> servers = segmentDescriptor.getServers(); + DataServerClient dataServerClient = makeDataServerClient(FixedSetServiceLocator.forDruidServerMetadata(servers)); + QueryToolChest<QueryType, Query<QueryType>> toolChest = warehouse.getToolChest(query); + Function<QueryType, QueryType> preComputeManipulatorFn = + toolChest.makePreComputeManipulatorFn(query, MetricManipulatorFns.deserializing()); + + final JavaType queryResultType = toolChest.getBaseResultType(); + final int numRetriesOnMissingSegments = preparedQuery.context().getNumRetriesOnMissingSegments(DEFAULT_NUM_TRIES); + + log.debug("Querying severs[%s] for segment[%s], retries:[%d]", servers, segmentDescriptor, numRetriesOnMissingSegments); + final ResponseContext responseContext = new DefaultResponseContext(); + + Pair<DataServerQueryStatus, Yielder<RowType>> statusSequencePair; + try { + statusSequencePair = RetryUtils.retry( + () -> { + Sequence<QueryType> sequence = dataServerClient.run(preparedQuery, responseContext, queryResultType, closer) + .map(preComputeManipulatorFn); + final List<SegmentDescriptor> missingSegments = getMissingSegments(responseContext); + // Only one segment is fetched, so this should be empty if it was fetched + if (missingSegments.isEmpty()) { + log.debug("Successfully fetched rows from server for segment[%s]", segmentDescriptor); + // Segment was found + Yielder<RowType> yielder = closer.register( + Yielders.each(mappingFunction.apply(sequence) + .map(row -> { + channelCounters.incrementRowCount(); + return row; + })) + ); + return Pair.of(DataServerQueryStatus.SUCCESS, yielder); + } else { + Boolean wasHandedOff = checkSegmentHandoff(coordinatorClient, dataSource, segmentDescriptor); + if (Boolean.TRUE.equals(wasHandedOff)) { + log.debug("Segment[%s] was handed off.", segmentDescriptor); Review Comment: Will add this as part of the counters -- 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]
