Java tutorial
/** * Copyright 2016 Twitter. All rights reserved. * * Licensed 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 com.twitter.graphjet.bipartite.edgepool; import java.util.Collections; import java.util.List; import java.util.Random; import java.util.Set; import java.util.concurrent.Callable; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import com.google.common.collect.Lists; import com.google.common.collect.Sets; import org.apache.commons.lang3.tuple.Pair; import static org.junit.Assert.assertEquals; import static org.junit.Assert.assertNull; import static org.junit.Assert.assertTrue; import it.unimi.dsi.fastutil.ints.Int2ObjectMap; import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap; import it.unimi.dsi.fastutil.ints.IntArrayList; import it.unimi.dsi.fastutil.ints.IntOpenHashSet; import it.unimi.dsi.fastutil.ints.IntSet; /** * This is a utility class that contains common paradigms for testing concurrent read-writes for * an {@link com.twitter.graphjet.bipartite.edgepool.EdgePool}. */ public final class EdgePoolConcurrentTestHelper { private EdgePoolConcurrentTestHelper() { // Utility class } /** * Helper class to allow reading from a * {@link com.twitter.graphjet.bipartite.edgepool.EdgePool} in a controlled manner. */ public static class EdgePoolReader implements Runnable { private final EdgePool edgePool; private final CountDownLatch startSignal; private final CountDownLatch doneSignal; private final int queryNode; private final int sleepTimeInMilliseconds; private int queryNodeDegree; private IntArrayList queryNodeEdges; public EdgePoolReader(EdgePool edgePool, CountDownLatch startSignal, CountDownLatch doneSignal, int queryNode, int sleepTimeInMilliseconds) { this.edgePool = edgePool; this.startSignal = startSignal; this.doneSignal = doneSignal; this.queryNode = queryNode; this.sleepTimeInMilliseconds = sleepTimeInMilliseconds; } @Override public void run() { try { startSignal.await(); Thread.sleep(sleepTimeInMilliseconds); } catch (InterruptedException e) { throw new RuntimeException("Unable to start waiting: ", e); } queryNodeDegree = edgePool.getNodeDegree(queryNode); if (queryNodeDegree > 0) { queryNodeEdges = new IntArrayList(edgePool.getNodeEdges(queryNode)); } doneSignal.countDown(); } public int getQueryNodeDegree() { return queryNodeDegree; } public IntArrayList getQueryNodeEdges() { return queryNodeEdges; } } /** * Helper class to allow writing to a * {@link com.twitter.graphjet.bipartite.edgepool.EdgePool} in a controlled manner. */ public static class EdgePoolWriter implements Runnable { private final EdgePool edgePool; private final List<WriterInfo> writerInfoList; public EdgePoolWriter(EdgePool edgePool, List<WriterInfo> writerInfoList) { this.edgePool = edgePool; this.writerInfoList = writerInfoList; } @Override public void run() { for (WriterInfo writerInfo : writerInfoList) { try { writerInfo.startSignal.await(); } catch (InterruptedException e) { throw new RuntimeException("Interrupted while waiting: ", e); } edgePool.addEdge(writerInfo.leftNode, writerInfo.rightNode); writerInfo.doneSignal.countDown(); } } } /** * This class encapsulates information needed by a writer to process a single edge. */ public static class WriterInfo { private final int leftNode; private final int rightNode; private final CountDownLatch startSignal; private final CountDownLatch doneSignal; public WriterInfo(int leftNode, int rightNode, CountDownLatch startSignal, CountDownLatch doneSignal) { this.leftNode = leftNode; this.rightNode = rightNode; this.startSignal = startSignal; this.doneSignal = doneSignal; } } /** * This helper method sets up a concurrent read-write situation with a single writer and multiple * readers that access the same underlying edgePool, and tests for correct edge access after * every single edge write via latches. This helps test write flushing after every edge insertion. * * @param edgePool is the underlying {@link com.twitter.graphjet.bipartite.edgepool.EdgePool} * @param edgesToAdd is a list of edges to add in the graph * @return the readers that store the state that they saw so that the state can be tested. There * is a reader for every edge insertion. */ public static List<EdgePoolReader> runConcurrentReadWriteThreads(EdgePool edgePool, List<Pair<Integer, Integer>> edgesToAdd) { int numReaders = edgesToAdd.size(); // start reading after first edge is written ExecutorService executor = Executors.newFixedThreadPool(numReaders + 1); // single writer List<CountDownLatch> readerStartLatches = Lists.newArrayListWithCapacity(numReaders); List<CountDownLatch> readerDoneLatches = Lists.newArrayListWithCapacity(numReaders); List<EdgePoolReader> readers = Lists.newArrayListWithCapacity(numReaders); for (Pair<Integer, Integer> edge : edgesToAdd) { CountDownLatch startLatch = new CountDownLatch(1); CountDownLatch doneLatch = new CountDownLatch(1); // Each time, get edges for the node added in the previous step EdgePoolReader edgePoolReader = new EdgePoolReader(edgePool, startLatch, doneLatch, edge.getLeft(), 0); readers.add(edgePoolReader); executor.submit(edgePoolReader); readerStartLatches.add(startLatch); readerDoneLatches.add(doneLatch); } /** * The start/done latches achieve the following execution order: writer, then reader 1, then * writer, then reader 2, and so on. As a concrete example, suppose we have two readers and a * writer, then the start/done latches are used as follows: * Initial latches state: * s1 = 1, d1 = 1 * s2 = 1, d2 = 1 * Execution steps: * - writer writes edge 1, sets s1 = 0 and waits on d1 * - reader 1 reads since s1 == 0 and sets d1 = 0 * - writer writes edge 2, sets s2 = 0 and waits on d2 * - reader 2 reads since s2 == 0 and sets d2 = 0 */ List<WriterInfo> writerInfo = Lists.newArrayListWithCapacity(edgesToAdd.size()); for (int i = 0; i < numReaders; i++) { // Start writing immediately at first, but then write an edge once the reader finishes reading // the previous edge CountDownLatch startLatch = (i > 0) ? readerDoneLatches.get(i - 1) : new CountDownLatch(0); // Release the next reader CountDownLatch doneLatch = readerStartLatches.get(i); writerInfo.add(new WriterInfo(edgesToAdd.get(i).getLeft(), edgesToAdd.get(i).getRight(), startLatch, doneLatch)); } executor.submit(new EdgePoolWriter(edgePool, writerInfo)); // Wait for all the processes to finish and then confirm that they did what they worked as // expected try { readerDoneLatches.get(numReaders - 1).await(); } catch (InterruptedException e) { throw new RuntimeException("Execution for last reader was interrupted: ", e); } return readers; } /** * This helper method sets up a concurrent read-write situation with a single writer and multiple * readers that access the same underlying edgePool, and tests for correct edge access during * simultaneous edge writes. This helps test read consistency during arbitrary points of * inserting edges. Note that the exact read-write sequence here is non-deterministic and would * vary depending on the machine, but the hope is that given the large number of readers the reads * would be done at many different points of edge insertion. The test itself checks only for * partial correctness (it could have false positives) so this should only be used as a supplement * to other testing. * * @param edgePool is the underlying * {@link com.twitter.graphjet.bipartite.edgepool.EdgePool} * @param numReadersPerNode is the number of reader threads to use per node * @param leftSize is the number of left nodes * @param rightSize is the number of right nodes * @param edgeProbability is the probability of an edge between a left-right node pair * @param random is the random number generator to use for generating a random graph */ public static void testRandomConcurrentReadWriteThreads(EdgePool edgePool, int numReadersPerNode, int leftSize, int rightSize, double edgeProbability, Random random) { int maxWaitingTimeForThreads = 20; // in milliseconds int numReaders = leftSize * numReadersPerNode; CountDownLatch readersDoneLatch = new CountDownLatch(numReaders); // First, construct a random set of edges to insert in the graph Set<Pair<Integer, Integer>> edges = Sets .newHashSetWithExpectedSize((int) (leftSize * rightSize * edgeProbability)); List<EdgePoolReader> readers = Lists.newArrayListWithCapacity(numReaders); Int2ObjectMap<IntSet> leftSideGraph = new Int2ObjectOpenHashMap<IntSet>(leftSize); int averageLeftDegree = (int) (rightSize * edgeProbability); for (int i = 0; i < leftSize; i++) { IntSet nodeEdges = new IntOpenHashSet(averageLeftDegree); for (int j = 0; j < rightSize; j++) { if (random.nextDouble() < edgeProbability) { nodeEdges.add(j); edges.add(Pair.of(i, j)); } } leftSideGraph.put(i, nodeEdges); } // Create a bunch of leftReaders per node that'll read from the graph at random for (int i = 0; i < leftSize; i++) { for (int j = 0; j < numReadersPerNode; j++) { readers.add(new EdgePoolReader(edgePool, new CountDownLatch(0), readersDoneLatch, i, random.nextInt(maxWaitingTimeForThreads))); } } // Create a single writer that will insert these edges in random order List<WriterInfo> writerInfo = Lists.newArrayListWithCapacity(edges.size()); List<Pair<Integer, Integer>> edgesList = Lists.newArrayList(edges); Collections.shuffle(edgesList); CountDownLatch writerDoneLatch = new CountDownLatch(edgesList.size()); for (Pair<Integer, Integer> edge : edgesList) { writerInfo.add(new WriterInfo(edge.getLeft(), edge.getRight(), new CountDownLatch(0), writerDoneLatch)); } ExecutorService executor = Executors.newFixedThreadPool(numReaders + 1); // single writer List<Callable<Integer>> allThreads = Lists.newArrayListWithCapacity(numReaders + 1); // First, we add the writer allThreads.add(Executors.callable(new EdgePoolWriter(edgePool, writerInfo), 1)); // then the readers for (int i = 0; i < numReaders; i++) { allThreads.add(Executors.callable(readers.get(i), 1)); } // these will execute in some non-deterministic order Collections.shuffle(allThreads, random); // Wait for all the processes to finish try { List<Future<Integer>> results = executor.invokeAll(allThreads, 10, TimeUnit.SECONDS); for (Future<Integer> result : results) { assertTrue(result.isDone()); assertEquals(1, result.get().intValue()); } } catch (InterruptedException e) { throw new RuntimeException("Execution for a thread was interrupted: ", e); } catch (ExecutionException e) { throw new RuntimeException("Execution issue in an executor thread: ", e); } // confirm that these worked as expected try { readersDoneLatch.await(); writerDoneLatch.await(); } catch (InterruptedException e) { throw new RuntimeException("Execution for last reader was interrupted: ", e); } // Check that all readers' read info is consistent with the graph for (EdgePoolReader reader : readers) { IntSet expectedEdges = leftSideGraph.get(reader.queryNode); assertTrue(reader.getQueryNodeDegree() <= expectedEdges.size()); if (reader.getQueryNodeDegree() == 0) { assertNull(reader.getQueryNodeEdges()); } else { for (int edge : reader.getQueryNodeEdges()) { assertTrue(expectedEdges.contains(edge)); } } } } }