Java tutorial
/* * 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.samza.execution; import com.google.common.annotations.VisibleForTesting; import com.google.common.collect.HashMultimap; import com.google.common.collect.Multimap; import java.util.Collection; import java.util.HashSet; import java.util.Optional; import java.util.Set; import org.apache.samza.SamzaException; import org.apache.samza.config.Config; import org.apache.samza.config.JobConfig; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import static org.apache.samza.execution.ExecutionPlanner.StreamSet; /** * {@link IntermediateStreamManager} calculates intermediate stream partitions based on the high-level application graph. */ class IntermediateStreamManager { private static final Logger log = LoggerFactory.getLogger(IntermediateStreamManager.class); private final Config config; @VisibleForTesting static final int MAX_INFERRED_PARTITIONS = 256; IntermediateStreamManager(Config config) { this.config = config; } /** * Calculates the number of partitions of all intermediate streams */ /* package private */ void calculatePartitions(JobGraph jobGraph, Collection<StreamSet> joinedStreamSets) { // Set partition count of intermediate streams participating in joins setJoinedIntermediateStreamPartitions(joinedStreamSets); // Set partition count of intermediate streams not participating in joins setIntermediateStreamPartitions(jobGraph); // Validate partition counts were assigned for all intermediate streams validateIntermediateStreamPartitions(jobGraph); } /** * Sets partition counts of intermediate streams which have not been assigned partition counts. */ private void setIntermediateStreamPartitions(JobGraph jobGraph) { final String defaultPartitionsConfigProperty = JobConfig.JOB_INTERMEDIATE_STREAM_PARTITIONS(); int partitions = config.getInt(defaultPartitionsConfigProperty, StreamEdge.PARTITIONS_UNKNOWN); if (partitions == StreamEdge.PARTITIONS_UNKNOWN) { // use the following simple algo to figure out the partitions // partition = MAX(MAX(Input topic partitions), MAX(Output topic partitions)) // partition will be further bounded by MAX_INFERRED_PARTITIONS. // This is important when running in hadoop where an HDFS input can have lots of files (partitions). int maxInPartitions = maxPartitions(jobGraph.getInputStreams()); int maxOutPartitions = maxPartitions(jobGraph.getOutputStreams()); partitions = Math.max(maxInPartitions, maxOutPartitions); if (partitions > MAX_INFERRED_PARTITIONS) { partitions = MAX_INFERRED_PARTITIONS; log.warn(String.format( "Inferred intermediate stream partition count %d is greater than the max %d. Using the max.", partitions, MAX_INFERRED_PARTITIONS)); } } else { // Reject any zero or other negative values explicitly specified in config. if (partitions <= 0) { throw new SamzaException(String.format("Invalid value %d specified for config property %s", partitions, defaultPartitionsConfigProperty)); } log.info("Using partition count value {} specified for config property {}", partitions, defaultPartitionsConfigProperty); } for (StreamEdge edge : jobGraph.getIntermediateStreamEdges()) { if (edge.getPartitionCount() <= 0) { log.info("Set the partition count for intermediate stream {} to {}.", edge.getName(), partitions); edge.setPartitionCount(partitions); } } } /** * Sets partition counts of intermediate streams participating in joins operations. */ private static void setJoinedIntermediateStreamPartitions(Collection<StreamSet> joinedStreamSets) { // Map every intermediate stream to all the stream-sets it appears in Multimap<StreamEdge, StreamSet> intermediateStreamToStreamSets = HashMultimap.create(); for (StreamSet streamSet : joinedStreamSets) { for (StreamEdge streamEdge : streamSet.getStreamEdges()) { if (streamEdge.getPartitionCount() == StreamEdge.PARTITIONS_UNKNOWN) { intermediateStreamToStreamSets.put(streamEdge, streamSet); } } } Set<StreamSet> streamSets = new HashSet<>(joinedStreamSets); Set<StreamSet> processedStreamSets = new HashSet<>(); while (!streamSets.isEmpty()) { // Retrieve and remove one stream set StreamSet streamSet = streamSets.iterator().next(); streamSets.remove(streamSet); // Find any stream with set partitions in this set Optional<StreamEdge> streamWithSetPartitions = streamSet.getStreamEdges().stream() .filter(streamEdge -> streamEdge.getPartitionCount() != StreamEdge.PARTITIONS_UNKNOWN) .findAny(); if (streamWithSetPartitions.isPresent()) { // Mark this stream-set as processed since we won't need to re-examine it ever again. // It is important that we do this first before processing any intermediate streams // that may be in this stream-set. processedStreamSets.add(streamSet); // Set partitions of all intermediate streams in this set (if any) int partitions = streamWithSetPartitions.get().getPartitionCount(); for (StreamEdge streamEdge : streamSet.getStreamEdges()) { if (streamEdge.getPartitionCount() == StreamEdge.PARTITIONS_UNKNOWN) { streamEdge.setPartitionCount(partitions); // Add all unprocessed stream-sets in which this intermediate stream appears Collection<StreamSet> streamSetsIncludingIntStream = intermediateStreamToStreamSets .get(streamEdge); streamSetsIncludingIntStream.stream().filter(s -> !processedStreamSets.contains(s)) .forEach(streamSets::add); } } } } } /** * Ensures all intermediate streams have been assigned partition counts. */ private static void validateIntermediateStreamPartitions(JobGraph jobGraph) { for (StreamEdge edge : jobGraph.getIntermediateStreamEdges()) { if (edge.getPartitionCount() <= 0) { throw new SamzaException( String.format("Failed to assign valid partition count to Stream %s", edge.getName())); } } } /* package private */ static int maxPartitions(Collection<StreamEdge> edges) { return edges.stream().mapToInt(StreamEdge::getPartitionCount).max().orElse(StreamEdge.PARTITIONS_UNKNOWN); } }