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.hadoop.hdfs; import org.junit.Test; import java.io.*; import java.util.ArrayList; import java.util.concurrent.CountDownLatch; import java.util.concurrent.atomic.AtomicReference; import org.apache.commons.logging.impl.Log4JLogger; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.hdfs.server.datanode.DataNode; import org.apache.hadoop.hdfs.server.namenode.FSNamesystem; import org.apache.hadoop.hdfs.server.namenode.LeaseManager; import org.apache.hadoop.hdfs.server.namenode.NameNode; import org.apache.hadoop.hdfs.server.protocol.InterDatanodeProtocol; import org.apache.log4j.Level; /** * This class tests the building blocks that are needed to * support HDFS appends. */ public class TestMultiThreadedSync { static final int blockSize = 1024 * 1024; static final int numBlocks = 10; static final int fileSize = numBlocks * blockSize + 1; private static final int NUM_THREADS = 10; private static final int WRITE_SIZE = 517; private static final int NUM_WRITES_PER_THREAD = 1000; private byte[] toWrite = null; /* * creates a file but does not close it */ private FSDataOutputStream createFile(FileSystem fileSys, Path name, int repl) throws IOException { FSDataOutputStream stm = fileSys.create(name, true, fileSys.getConf().getInt("io.file.buffer.size", 4096), (short) repl, (long) blockSize); return stm; } private void initBuffer(int size) { long seed = AppendTestUtil.nextLong(); toWrite = AppendTestUtil.randomBytes(seed, size); } @Test public void testMultipleSyncers() throws Exception { Configuration conf = new Configuration(); MiniDFSCluster cluster = new MiniDFSCluster(conf, 1, true, null); FileSystem fs = cluster.getFileSystem(); Path p = new Path("/multiple-syncers.dat"); try { doMultithreadedWrites(conf, p, NUM_THREADS, WRITE_SIZE, NUM_WRITES_PER_THREAD); } finally { fs.close(); cluster.shutdown(); } } /** * Test case where a bunch of threads are continuously calling sync() while another * thread appends some data and then closes the file. * * The syncing threads should eventually catch an IOException stating that the stream * was closed -- and not an NPE or anything like that. */ @Test public void testSyncWhileClosing() throws Throwable { Configuration conf = new Configuration(); MiniDFSCluster cluster = new MiniDFSCluster(conf, 1, true, null); FileSystem fs = cluster.getFileSystem(); Path p = new Path("/sync-and-close.dat"); final FSDataOutputStream stm = createFile(fs, p, 1); ArrayList<Thread> flushers = new ArrayList<Thread>(); final AtomicReference<Throwable> thrown = new AtomicReference<Throwable>(); try { for (int i = 0; i < 10; i++) { Thread flusher = new Thread() { public void run() { try { while (true) { try { stm.sync(); } catch (IOException ioe) { if (!ioe.toString().contains("DFSOutputStream is closed")) { throw ioe; } else { return; } } } } catch (Throwable t) { thrown.set(t); } } }; flusher.start(); flushers.add(flusher); } // Write some data for (int i = 0; i < 10000; i++) { stm.write(1); } // Close it while the flushing threads are still flushing stm.close(); // Wait for the flushers to all die. for (Thread t : flushers) { t.join(); } // They should have all gotten the expected exception, not anything // else. if (thrown.get() != null) { throw thrown.get(); } } finally { fs.close(); cluster.shutdown(); } } public void doMultithreadedWrites(Configuration conf, Path p, int numThreads, int bufferSize, int numWrites) throws Exception { initBuffer(bufferSize); // create a new file. FileSystem fs = p.getFileSystem(conf); FSDataOutputStream stm = createFile(fs, p, 1); System.out.println("Created file simpleFlush.dat"); // TODO move this bit to another test case // There have been a couple issues with flushing empty buffers, so do // some empty flushes first. stm.sync(); stm.sync(); stm.write(1); stm.sync(); stm.sync(); CountDownLatch countdown = new CountDownLatch(1); ArrayList<Thread> threads = new ArrayList<Thread>(); AtomicReference<Throwable> thrown = new AtomicReference<Throwable>(); for (int i = 0; i < numThreads; i++) { Thread t = new AppendTestUtil.WriterThread(stm, toWrite, thrown, countdown, numWrites); threads.add(t); t.start(); } // Start all the threads at the same time for maximum raciness! countdown.countDown(); for (Thread t : threads) { t.join(); } if (thrown.get() != null) { throw new RuntimeException("Deferred", thrown.get()); } stm.close(); System.out.println("Closed file."); } public static void main(String args[]) throws Exception { TestMultiThreadedSync test = new TestMultiThreadedSync(); Configuration conf = new Configuration(); Path p = new Path("/user/todd/test.dat"); long st = System.nanoTime(); test.doMultithreadedWrites(conf, p, 10, 511, 50000); long et = System.nanoTime(); System.out.println("Finished in " + ((et - st) / 1000000) + "ms"); } }