/**
* 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.server.namenode;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.impl.Log4JLogger;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.permission.*;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSTestUtil;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.hdfs.MiniDFSCluster;
import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
import org.apache.hadoop.hdfs.server.namenode.EditLogFileInputStream;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NamenodeRole;
import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
import org.apache.log4j.Level;
import static org.junit.Assert.*;
import org.junit.Test;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import static org.mockito.Mockito.*;
/**
* This class tests various synchronization bugs in FSEditLog rolling
* and namespace saving.
*/
public class TestEditLogRace {
static {
((Log4JLogger)FSEditLog.LOG).getLogger().setLevel(Level.ALL);
}
private static final Log LOG = LogFactory.getLog(TestEditLogRace.class);
private static final String NAME_DIR =
MiniDFSCluster.getBaseDirectory() + "name1";
// This test creates NUM_THREADS threads and each thread continuously writes
// transactions
static final int NUM_THREADS = 16;
/**
* The number of times to roll the edit log during the test. Since this
* tests for a race condition, higher numbers are more likely to find
* a bug if it exists, but the test will take longer.
*/
static final int NUM_ROLLS = 30;
/**
* The number of times to save the fsimage and create an empty edit log.
*/
static final int NUM_SAVE_IMAGE = 30;
private List<Transactions> workers = new ArrayList<Transactions>();
private static final int NUM_DATA_NODES = 1;
/**
* Several of the test cases work by introducing a sleep
* into an operation that is usually fast, and then verifying
* that another operation blocks for at least this amount of time.
* This value needs to be significantly longer than the average
* time for an fsync() or enterSafeMode().
*/
private static final int BLOCK_TIME = 10;
//
// an object that does a bunch of transactions
//
static class Transactions implements Runnable {
FSNamesystem namesystem;
short replication = 3;
long blockSize = 64;
volatile boolean stopped = false;
volatile Thread thr;
AtomicReference<Throwable> caught;
Transactions(FSNamesystem ns, AtomicReference<Throwable> caught) {
namesystem = ns;
this.caught = caught;
}
// add a bunch of transactions.
public void run() {
thr = Thread.currentThread();
PermissionStatus p = namesystem.createFsOwnerPermissions(
new FsPermission((short)0777));
int i = 0;
while (!stopped) {
try {
String dirname = "/thr-" + thr.getId() + "-dir-" + i;
namesystem.mkdirs(dirname, p, true);
namesystem.delete(dirname, true);
} catch (SafeModeException sme) {
// This is OK - the tests will bring NN in and out of safemode
} catch (Throwable e) {
LOG.warn("Got error in transaction thread", e);
caught.compareAndSet(null, e);
break;
}
i++;
}
}
public void stop() {
stopped = true;
}
public Thread getThread() {
return thr;
}
}
private void startTransactionWorkers(FSNamesystem namesystem,
AtomicReference<Throwable> caughtErr) {
// Create threads and make them run transactions concurrently.
for (int i = 0; i < NUM_THREADS; i++) {
Transactions trans = new Transactions(namesystem, caughtErr);
new Thread(trans, "TransactionThread-" + i).start();
workers.add(trans);
}
}
private void stopTransactionWorkers() {
// wait for all transactions to get over
for (Transactions worker : workers) {
worker.stop();
}
for (Transactions worker : workers) {
Thread thr = worker.getThread();
try {
if (thr != null) thr.join();
} catch (InterruptedException ie) {}
}
}
/**
* Tests rolling edit logs while transactions are ongoing.
*/
@Test
public void testEditLogRolling() throws Exception {
// start a cluster
Configuration conf = new HdfsConfiguration();
MiniDFSCluster cluster = null;
FileSystem fileSys = null;
AtomicReference<Throwable> caughtErr = new AtomicReference<Throwable>();
try {
cluster = new MiniDFSCluster.Builder(conf).numDataNodes(NUM_DATA_NODES).build();
cluster.waitActive();
fileSys = cluster.getFileSystem();
final FSNamesystem namesystem = cluster.getNamesystem();
FSImage fsimage = namesystem.getFSImage();
FSEditLog editLog = fsimage.getEditLog();
StorageDirectory sd = fsimage.getStorage().getStorageDir(0);
startTransactionWorkers(namesystem, caughtErr);
long previousLogTxId = 1;
for (int i = 0; i < NUM_ROLLS && caughtErr.get() == null; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {}
LOG.info("Starting roll " + i + ".");
CheckpointSignature sig = namesystem.rollEditLog();
long nextLog = sig.curSegmentTxId;
String logFileName = NNStorage.getFinalizedEditsFileName(
previousLogTxId, nextLog - 1);
previousLogTxId += verifyEditLogs(namesystem, fsimage, logFileName, previousLogTxId);
assertEquals(previousLogTxId, nextLog);
File expectedLog = NNStorage.getInProgressEditsFile(sd, previousLogTxId);
assertTrue("Expect " + expectedLog + " to exist", expectedLog.exists());
}
} finally {
stopTransactionWorkers();
if (caughtErr.get() != null) {
throw new RuntimeException(caughtErr.get());
}
if(fileSys != null) fileSys.close();
if(cluster != null) cluster.shutdown();
}
}
private long verifyEditLogs(FSNamesystem namesystem, FSImage fsimage,
String logFileName, long startTxId)
throws IOException {
long numEdits = -1;
// Verify that we can read in all the transactions that we have written.
// If there were any corruptions, it is likely that the reading in
// of these transactions will throw an exception.
for (StorageDirectory sd :
fsimage.getStorage().dirIterable(NameNodeDirType.EDITS)) {
File editFile = new File(sd.getCurrentDir(), logFileName);
System.out.println("Verifying file: " + editFile);
FSEditLogLoader loader = new FSEditLogLoader(namesystem);
int numEditsThisLog = loader.loadFSEdits(new EditLogFileInputStream(editFile),
startTxId);
System.out.println("Number of edits: " + numEditsThisLog);
assertTrue(numEdits == -1 || numEditsThisLog == numEdits);
numEdits = numEditsThisLog;
}
assertTrue(numEdits != -1);
return numEdits;
}
/**
* Tests saving fs image while transactions are ongoing.
*/
@Test
public void testSaveNamespace() throws Exception {
// start a cluster
Configuration conf = new HdfsConfiguration();
MiniDFSCluster cluster = null;
FileSystem fileSys = null;
AtomicReference<Throwable> caughtErr = new AtomicReference<Throwable>();
try {
cluster = new MiniDFSCluster.Builder(conf).numDataNodes(NUM_DATA_NODES).build();
cluster.waitActive();
fileSys = cluster.getFileSystem();
final FSNamesystem namesystem = cluster.getNamesystem();
FSImage fsimage = namesystem.getFSImage();
FSEditLog editLog = fsimage.getEditLog();
startTransactionWorkers(namesystem, caughtErr);
for (int i = 0; i < NUM_SAVE_IMAGE && caughtErr.get() == null; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {}
LOG.info("Save " + i + ": entering safe mode");
namesystem.enterSafeMode(false);
// Verify edit logs before the save
// They should start with the first edit after the checkpoint
long logStartTxId = fsimage.getStorage().getMostRecentCheckpointTxId() + 1;
verifyEditLogs(namesystem, fsimage,
NNStorage.getInProgressEditsFileName(logStartTxId),
logStartTxId);
LOG.info("Save " + i + ": saving namespace");
namesystem.saveNamespace();
LOG.info("Save " + i + ": leaving safemode");
long savedImageTxId = fsimage.getStorage().getMostRecentCheckpointTxId();
// Verify that edit logs post save got finalized and aren't corrupt
verifyEditLogs(namesystem, fsimage,
NNStorage.getFinalizedEditsFileName(logStartTxId, savedImageTxId),
logStartTxId);
// The checkpoint id should be 1 less than the last written ID, since
// the log roll writes the "BEGIN" transaction to the new log.
assertEquals(fsimage.getStorage().getMostRecentCheckpointTxId(),
editLog.getLastWrittenTxId() - 1);
namesystem.leaveSafeMode(false);
LOG.info("Save " + i + ": complete");
}
} finally {
stopTransactionWorkers();
if (caughtErr.get() != null) {
throw new RuntimeException(caughtErr.get());
}
if(fileSys != null) fileSys.close();
if(cluster != null) cluster.shutdown();
}
}
private Configuration getConf() {
Configuration conf = new HdfsConfiguration();
FileSystem.setDefaultUri(conf, "hdfs://localhost:0");
conf.set(DFSConfigKeys.DFS_NAMENODE_HTTP_ADDRESS_KEY, "0.0.0.0:0");
conf.set(DFSConfigKeys.DFS_NAMENODE_NAME_DIR_KEY, NAME_DIR);
conf.set(DFSConfigKeys.DFS_NAMENODE_EDITS_DIR_KEY, NAME_DIR);
conf.setBoolean(DFSConfigKeys.DFS_PERMISSIONS_ENABLED_KEY, false);
return conf;
}
/**
* The logSync() method in FSEditLog is unsynchronized whiel syncing
* so that other threads can concurrently enqueue edits while the prior
* sync is ongoing. This test checks that the log is saved correctly
* if the saveImage occurs while the syncing thread is in the unsynchronized middle section.
*
* This replicates the following manual test proposed by Konstantin:
* I start the name-node in debugger.
* I do -mkdir and stop the debugger in logSync() just before it does flush.
* Then I enter safe mode with another client
* I start saveNamepsace and stop the debugger in
* FSImage.saveFSImage() -> FSEditLog.createEditLogFile()
* -> EditLogFileOutputStream.create() ->
* after truncating the file but before writing LAYOUT_VERSION into it.
* Then I let logSync() run.
* Then I terminate the name-node.
* After that the name-node wont start, since the edits file is broken.
*/
@Test
public void testSaveImageWhileSyncInProgress() throws Exception {
Configuration conf = getConf();
NameNode.initMetrics(conf, NamenodeRole.NAMENODE);
DFSTestUtil.formatNameNode(conf);
final FSNamesystem namesystem = new FSNamesystem(conf);
try {
FSImage fsimage = namesystem.getFSImage();
FSEditLog editLog = fsimage.getEditLog();
FSEditLog.JournalAndStream jas = editLog.getJournals().get(0);
EditLogFileOutputStream spyElos =
spy((EditLogFileOutputStream)jas.getCurrentStream());
jas.setCurrentStreamForTests(spyElos);
final AtomicReference<Throwable> deferredException =
new AtomicReference<Throwable>();
final CountDownLatch waitToEnterFlush = new CountDownLatch(1);
final Thread doAnEditThread = new Thread() {
public void run() {
try {
LOG.info("Starting mkdirs");
namesystem.mkdirs("/test",
new PermissionStatus("test","test", new FsPermission((short)00755)),
true);
LOG.info("mkdirs complete");
} catch (Throwable ioe) {
deferredException.set(ioe);
waitToEnterFlush.countDown();
}
}
};
Answer<Void> blockingFlush = new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) throws Throwable {
LOG.info("Flush called");
if (Thread.currentThread() == doAnEditThread) {
LOG.info("edit thread: Telling main thread we made it to flush section...");
// Signal to main thread that the edit thread is in the racy section
waitToEnterFlush.countDown();
LOG.info("edit thread: sleeping for " + BLOCK_TIME + "secs");
Thread.sleep(BLOCK_TIME*1000);
LOG.info("Going through to flush. This will allow the main thread to continue.");
}
invocation.callRealMethod();
LOG.info("Flush complete");
return null;
}
};
doAnswer(blockingFlush).when(spyElos).flush();
doAnEditThread.start();
// Wait for the edit thread to get to the logsync unsynchronized section
LOG.info("Main thread: waiting to enter flush...");
waitToEnterFlush.await();
assertNull(deferredException.get());
LOG.info("Main thread: detected that logSync is in unsynchronized section.");
LOG.info("Trying to enter safe mode.");
LOG.info("This should block for " + BLOCK_TIME + "sec, since flush will sleep that long");
long st = System.currentTimeMillis();
namesystem.setSafeMode(SafeModeAction.SAFEMODE_ENTER);
long et = System.currentTimeMillis();
LOG.info("Entered safe mode");
// Make sure we really waited for the flush to complete!
assertTrue(et - st > (BLOCK_TIME - 1)*1000);
// Once we're in safe mode, save namespace.
namesystem.saveNamespace();
LOG.info("Joining on edit thread...");
doAnEditThread.join();
assertNull(deferredException.get());
// We did 3 edits: begin, txn, and end
assertEquals(3, verifyEditLogs(namesystem, fsimage,
NNStorage.getFinalizedEditsFileName(1, 3),
1));
// after the save, just the one "begin"
assertEquals(1, verifyEditLogs(namesystem, fsimage,
NNStorage.getInProgressEditsFileName(4),
4));
} finally {
LOG.info("Closing namesystem");
if(namesystem != null) namesystem.close();
}
}
/**
* Most of the FSNamesystem methods have a synchronized section where they
* update the name system itself and write to the edit log, and then
* unsynchronized, they call logSync. This test verifies that, if an
* operation has written to the edit log but not yet synced it,
* we wait for that sync before entering safe mode.
*/
@Test
public void testSaveRightBeforeSync() throws Exception {
Configuration conf = getConf();
NameNode.initMetrics(conf, NamenodeRole.NAMENODE);
DFSTestUtil.formatNameNode(conf);
final FSNamesystem namesystem = new FSNamesystem(conf);
try {
FSImage fsimage = namesystem.getFSImage();
FSEditLog editLog = spy(fsimage.getEditLog());
fsimage.editLog = editLog;
final AtomicReference<Throwable> deferredException =
new AtomicReference<Throwable>();
final CountDownLatch waitToEnterSync = new CountDownLatch(1);
final Thread doAnEditThread = new Thread() {
public void run() {
try {
LOG.info("Starting mkdirs");
namesystem.mkdirs("/test",
new PermissionStatus("test","test", new FsPermission((short)00755)),
true);
LOG.info("mkdirs complete");
} catch (Throwable ioe) {
deferredException.set(ioe);
waitToEnterSync.countDown();
}
}
};
Answer<Void> blockingSync = new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) throws Throwable {
LOG.info("logSync called");
if (Thread.currentThread() == doAnEditThread) {
LOG.info("edit thread: Telling main thread we made it just before logSync...");
waitToEnterSync.countDown();
LOG.info("edit thread: sleeping for " + BLOCK_TIME + "secs");
Thread.sleep(BLOCK_TIME*1000);
LOG.info("Going through to logSync. This will allow the main thread to continue.");
}
invocation.callRealMethod();
LOG.info("logSync complete");
return null;
}
};
doAnswer(blockingSync).when(editLog).logSync();
doAnEditThread.start();
LOG.info("Main thread: waiting to just before logSync...");
waitToEnterSync.await();
assertNull(deferredException.get());
LOG.info("Main thread: detected that logSync about to be called.");
LOG.info("Trying to enter safe mode.");
LOG.info("This should block for " + BLOCK_TIME + "sec, since we have pending edits");
long st = System.currentTimeMillis();
namesystem.setSafeMode(SafeModeAction.SAFEMODE_ENTER);
long et = System.currentTimeMillis();
LOG.info("Entered safe mode");
// Make sure we really waited for the flush to complete!
assertTrue(et - st > (BLOCK_TIME - 1)*1000);
// Once we're in safe mode, save namespace.
namesystem.saveNamespace();
LOG.info("Joining on edit thread...");
doAnEditThread.join();
assertNull(deferredException.get());
// We did 3 edits: begin, txn, and end
assertEquals(3, verifyEditLogs(namesystem, fsimage,
NNStorage.getFinalizedEditsFileName(1, 3),
1));
// after the save, just the one "begin"
assertEquals(1, verifyEditLogs(namesystem, fsimage,
NNStorage.getInProgressEditsFileName(4),
4));
} finally {
LOG.info("Closing namesystem");
if(namesystem != null) namesystem.close();
}
}
}