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.drill.exec.store.schedule; import java.util.Collections; import java.util.Comparator; import java.util.Iterator; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.concurrent.TimeUnit; import com.carrotsearch.hppc.cursors.ObjectLongCursor; import com.google.common.collect.Iterators; import com.google.common.collect.Maps; import org.apache.drill.common.exceptions.DrillRuntimeException; import org.apache.drill.exec.ExecConstants; import org.apache.drill.exec.proto.CoordinationProtos.DrillbitEndpoint; import com.google.common.base.Stopwatch; import com.google.common.collect.ArrayListMultimap; import com.google.common.collect.ListMultimap; import com.google.common.collect.Lists; import org.apache.drill.exec.server.DrillbitContext; /** * The AssignmentCreator is responsible for assigning a set of work units to the available slices. */ public class AssignmentCreator<T extends CompleteWork> { static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(AssignmentCreator.class); /** * Comparator used to sort in order of decreasing affinity */ private static Comparator<Entry<DrillbitEndpoint, Long>> comparator = new Comparator<Entry<DrillbitEndpoint, Long>>() { @Override public int compare(Entry<DrillbitEndpoint, Long> o1, Entry<DrillbitEndpoint, Long> o2) { return (int) (o1.getValue() - o2.getValue()); } }; /** * the maximum number of work units to assign to any minor fragment */ private int maxWork; /** * The units of work to be assigned */ private List<T> units; /** * Mappings */ private ArrayListMultimap<Integer, T> mappings = ArrayListMultimap.create(); /** * A list of DrillbitEndpoints, where the index in the list corresponds to the minor fragment id */ private List<DrillbitEndpoint> incomingEndpoints; private AssignmentCreator(List<DrillbitEndpoint> incomingEndpoints, List<T> units) { this.incomingEndpoints = incomingEndpoints; this.units = units; } /** * Assign each unit of work to a minor fragment, given that a list of DrillbitEndpoints, whose index in the list correspond * to the minor fragment id for each fragment. A given DrillbitEndpoint can appear multiple times in this list. This method * will try to assign work based on the affinity of each work unit, but will also evenly distribute the work units among * all of the minor fragments * * @param incomingEndpoints The list of incomingEndpoints, indexed by minor fragment id * @param units the list of work units to be assigned * @return A multimap that maps each minor fragment id to a list of work units */ public static <T extends CompleteWork> ListMultimap<Integer, T> getMappings( List<DrillbitEndpoint> incomingEndpoints, List<T> units, DrillbitContext context) { boolean useOldAssignmentCode = context == null ? false : context.getOptionManager().getOption(ExecConstants.USE_OLD_ASSIGNMENT_CREATOR).bool_val; if (useOldAssignmentCode) { return OldAssignmentCreator.getMappings(incomingEndpoints, units); } else { AssignmentCreator<T> creator = new AssignmentCreator(incomingEndpoints, units); return creator.getMappings(); } } /** * Does the work of creating the mappings for this AssignmentCreator * @return the minor fragment id to work units mapping */ private ListMultimap<Integer, T> getMappings() { Stopwatch watch = new Stopwatch(); watch.start(); maxWork = (int) Math.ceil(units.size() / ((float) incomingEndpoints.size())); LinkedList<WorkEndpointListPair<T>> workList = getWorkList(); LinkedList<WorkEndpointListPair<T>> unassignedWorkList; Map<DrillbitEndpoint, FragIteratorWrapper> endpointIterators = getEndpointIterators(); unassignedWorkList = assign(workList, endpointIterators, true); assignLeftovers(unassignedWorkList, endpointIterators, true); assignLeftovers(unassignedWorkList, endpointIterators, false); if (unassignedWorkList.size() != 0) { throw new DrillRuntimeException("There are still unassigned work units"); } logger.debug("Took {} ms to assign {} work units to {} fragments", watch.elapsed(TimeUnit.MILLISECONDS), units.size(), incomingEndpoints.size()); return mappings; } /** * * @param workList the list of work units to assign * @param endpointIterators the endpointIterators to assign to * @param assignMinimum whether to assign only up to the minimum required * @return a list of unassigned work units */ private LinkedList<WorkEndpointListPair<T>> assign(List<WorkEndpointListPair<T>> workList, Map<DrillbitEndpoint, FragIteratorWrapper> endpointIterators, boolean assignMinimum) { LinkedList<WorkEndpointListPair<T>> currentUnassignedList = Lists.newLinkedList(); outer: for (WorkEndpointListPair<T> workPair : workList) { List<DrillbitEndpoint> endpoints = workPair.sortedEndpoints; for (DrillbitEndpoint endpoint : endpoints) { FragIteratorWrapper iteratorWrapper = endpointIterators.get(endpoint); if (iteratorWrapper == null) { continue; } if (iteratorWrapper.count < (assignMinimum ? iteratorWrapper.minCount : iteratorWrapper.maxCount)) { Integer assignment = iteratorWrapper.iter.next(); iteratorWrapper.count++; mappings.put(assignment, workPair.work); continue outer; } } currentUnassignedList.add(workPair); } return currentUnassignedList; } /** * * @param unassignedWorkList the work units to assign * @param endpointIterators the endpointIterators to assign to * @param assignMinimum wheterh to assign the minimum amount */ private void assignLeftovers(LinkedList<WorkEndpointListPair<T>> unassignedWorkList, Map<DrillbitEndpoint, FragIteratorWrapper> endpointIterators, boolean assignMinimum) { outer: for (FragIteratorWrapper iteratorWrapper : endpointIterators.values()) { while (iteratorWrapper.count < (assignMinimum ? iteratorWrapper.minCount : iteratorWrapper.maxCount)) { WorkEndpointListPair<T> workPair = unassignedWorkList.poll(); if (workPair == null) { break outer; } Integer assignment = iteratorWrapper.iter.next(); iteratorWrapper.count++; mappings.put(assignment, workPair.work); } } } /** * Builds the list of WorkEndpointListPairs, which pair a work unit with a list of endpoints sorted by affinity * @return the list of WorkEndpointListPairs */ private LinkedList<WorkEndpointListPair<T>> getWorkList() { Stopwatch watch = new Stopwatch(); watch.start(); LinkedList<WorkEndpointListPair<T>> workList = Lists.newLinkedList(); for (T work : units) { List<Map.Entry<DrillbitEndpoint, Long>> entries = Lists.newArrayList(); for (ObjectLongCursor<DrillbitEndpoint> cursor : work.getByteMap()) { final DrillbitEndpoint ep = cursor.key; final Long val = cursor.value; Map.Entry<DrillbitEndpoint, Long> entry = new Entry() { @Override public Object getKey() { return ep; } @Override public Object getValue() { return val; } @Override public Object setValue(Object value) { throw new UnsupportedOperationException(); } }; entries.add(entry); } Collections.sort(entries, comparator); List<DrillbitEndpoint> sortedEndpoints = Lists.newArrayList(); for (Entry<DrillbitEndpoint, Long> entry : entries) { sortedEndpoints.add(entry.getKey()); } workList.add(new WorkEndpointListPair<T>(work, sortedEndpoints)); } return workList; } /** * A wrapper class around a work unit and its associated sort list of Endpoints (sorted by affinity in decreasing order) */ private static class WorkEndpointListPair<T> { T work; List<DrillbitEndpoint> sortedEndpoints; WorkEndpointListPair(T work, List<DrillbitEndpoint> sortedEndpoints) { this.work = work; this.sortedEndpoints = sortedEndpoints; } } /** * Groups minor fragments together by corresponding endpoint, and creates an iterator that can be used to evenly * distribute work assigned to a given endpoint to all corresponding minor fragments evenly * * @return */ private Map<DrillbitEndpoint, FragIteratorWrapper> getEndpointIterators() { Stopwatch watch = new Stopwatch(); watch.start(); Map<DrillbitEndpoint, FragIteratorWrapper> map = Maps.newLinkedHashMap(); Map<DrillbitEndpoint, List<Integer>> mmap = Maps.newLinkedHashMap(); for (int i = 0; i < incomingEndpoints.size(); i++) { DrillbitEndpoint endpoint = incomingEndpoints.get(i); List<Integer> intList = mmap.get(incomingEndpoints.get(i)); if (intList == null) { intList = Lists.newArrayList(); } intList.add(Integer.valueOf(i)); mmap.put(endpoint, intList); } for (DrillbitEndpoint endpoint : mmap.keySet()) { FragIteratorWrapper wrapper = new FragIteratorWrapper(); wrapper.iter = Iterators.cycle(mmap.get(endpoint)); wrapper.maxCount = maxWork * mmap.get(endpoint).size(); wrapper.minCount = Math.max(maxWork - 1, 1) * mmap.get(endpoint).size(); map.put(endpoint, wrapper); } return map; } /** * A struct that holds a fragment iterator and keeps track of how many units have been assigned, as well as the maximum * number of assignment it will accept */ private static class FragIteratorWrapper { int count = 0; int maxCount; int minCount; Iterator<Integer> iter; } }