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HDFS-9589. Block files which have been hardlinked should be duplicated before the DataNode appends to the them (cmccabe)

This commit is contained in:
Colin Patrick Mccabe 2015-12-21 14:13:36 -08:00
parent 70d6f20126
commit bb540ba85a
5 changed files with 159 additions and 0 deletions
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3
hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -2541,6 +2541,9 @@ Release 2.8.0 - UNRELEASED
HDFS-9347. Invariant assumption in TestQuorumJournalManager.shutdown()
is wrong. (Wei-Chiu Chuang via zhz)
HDFS-9589. Block files which have been hardlinked should be duplicated
before the DataNode appends to the them (cmccabe)
Release 2.7.3 - UNRELEASED
INCOMPATIBLE CHANGES

79
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInfo.java
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@ -18,12 +18,18 @@
package org.apache.hadoop.hdfs.server.datanode;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.HardLink;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.util.LightWeightResizableGSet;
import com.google.common.annotations.VisibleForTesting;
@ -210,6 +216,79 @@ abstract public class ReplicaInfo extends Block
return 0;
}
/**
* Copy specified file into a temporary file. Then rename the
* temporary file to the original name. This will cause any
* hardlinks to the original file to be removed. The temporary
* files are created in the same directory. The temporary files will
* be recovered (especially on Windows) on datanode restart.
*/
private void breakHardlinks(File file, Block b) throws IOException {
File tmpFile = DatanodeUtil.createTmpFile(b, DatanodeUtil.getUnlinkTmpFile(file));
try {
FileInputStream in = new FileInputStream(file);
try {
FileOutputStream out = new FileOutputStream(tmpFile);
try {
IOUtils.copyBytes(in, out, 16 * 1024);
} finally {
out.close();
}
} finally {
in.close();
}
if (file.length() != tmpFile.length()) {
throw new IOException("Copy of file " + file + " size " + file.length()+
" into file " + tmpFile +
" resulted in a size of " + tmpFile.length());
}
FileUtil.replaceFile(tmpFile, file);
} catch (IOException e) {
boolean done = tmpFile.delete();
if (!done) {
DataNode.LOG.info("detachFile failed to delete temporary file " +
tmpFile);
}
throw e;
}
}
/**
* This function "breaks hardlinks" to the current replica file.
*
* When doing a DataNode upgrade, we create a bunch of hardlinks to each block
* file. This cleverly ensures that both the old and the new storage
* directories can contain the same block file, without using additional space
* for the data.
*
* However, when we want to append to the replica file, we need to "break" the
* hardlink to ensure that the old snapshot continues to contain the old data
* length. If we failed to do that, we could roll back to the previous/
* directory during a downgrade, and find that the block contents were longer
* than they were at the time of upgrade.
*
* @return true only if data was copied.
* @throws IOException
*/
public boolean breakHardLinksIfNeeded() throws IOException {
File file = getBlockFile();
if (file == null || getVolume() == null) {
throw new IOException("detachBlock:Block not found. " + this);
}
File meta = getMetaFile();
int linkCount = HardLink.getLinkCount(file);
if (linkCount > 1) {
DataNode.LOG.info("Breaking hardlink for " + linkCount + "x-linked " +
"block " + this);
breakHardlinks(file, this);
}
if (HardLink.getLinkCount(meta) > 1) {
breakHardlinks(meta, this);
}
return true;
}
@Override //Object
public String toString() {
return getClass().getSimpleName()

5
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
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@ -1128,6 +1128,10 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
throws IOException {
// If the block is cached, start uncaching it.
cacheManager.uncacheBlock(bpid, replicaInfo.getBlockId());
// If there are any hardlinks to the block, break them. This ensures we are
// not appending to a file that is part of a previous/ directory.
replicaInfo.breakHardLinksIfNeeded();
// construct a RBW replica with the new GS
File blkfile = replicaInfo.getBlockFile();
@ -2493,6 +2497,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
+ ", rur=" + rur);
}
if (rur.getNumBytes() > newlength) {
rur.breakHardLinksIfNeeded();
truncateBlock(blockFile, metaFile, rur.getNumBytes(), newlength);
if(!copyOnTruncate) {
// update RUR with the new length

66
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestFileAppend.java
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@ -43,6 +43,8 @@ import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
import org.apache.hadoop.hdfs.server.datanode.DataNode;
import org.apache.hadoop.hdfs.server.datanode.DataNodeTestUtils;
import org.apache.hadoop.hdfs.server.datanode.SimulatedFSDataset;
import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetTestUtil;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.ipc.RemoteException;
import org.junit.Assert;
@ -109,6 +111,70 @@ public class TestFileAppend{
expected, "Read 1", false);
}
@Test
public void testBreakHardlinksIfNeeded() throws IOException {
Configuration conf = new HdfsConfiguration();
if (simulatedStorage) {
SimulatedFSDataset.setFactory(conf);
}
MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
FileSystem fs = cluster.getFileSystem();
InetSocketAddress addr = new InetSocketAddress("localhost",
cluster.getNameNodePort());
DFSClient client = new DFSClient(addr, conf);
try {
// create a new file, write to it and close it.
Path file1 = new Path("/filestatus.dat");
FSDataOutputStream stm = AppendTestUtil.createFile(fs, file1, 1);
writeFile(stm);
stm.close();
// Get a handle to the datanode
DataNode[] dn = cluster.listDataNodes();
assertTrue("There should be only one datanode but found " + dn.length,
dn.length == 1);
LocatedBlocks locations = client.getNamenode().getBlockLocations(
file1.toString(), 0, Long.MAX_VALUE);
List<LocatedBlock> blocks = locations.getLocatedBlocks();
final FsDatasetSpi<?> fsd = dn[0].getFSDataset();
//
// Create hard links for a few of the blocks
//
for (int i = 0; i < blocks.size(); i = i + 2) {
ExtendedBlock b = blocks.get(i).getBlock();
final File f = FsDatasetTestUtil.getBlockFile(
fsd, b.getBlockPoolId(), b.getLocalBlock());
File link = new File(f.toString() + ".link");
System.out.println("Creating hardlink for File " + f + " to " + link);
HardLink.createHardLink(f, link);
}
// Detach all blocks. This should remove hardlinks (if any)
for (int i = 0; i < blocks.size(); i++) {
ExtendedBlock b = blocks.get(i).getBlock();
System.out.println("breakHardlinksIfNeeded detaching block " + b);
assertTrue("breakHardlinksIfNeeded(" + b + ") should have returned true",
FsDatasetTestUtil.breakHardlinksIfNeeded(fsd, b));
}
// Since the blocks were already detached earlier, these calls should
// return false
for (int i = 0; i < blocks.size(); i++) {
ExtendedBlock b = blocks.get(i).getBlock();
System.out.println("breakHardlinksIfNeeded re-attempting to " +
"detach block " + b);
assertTrue("breakHardlinksIfNeeded(" + b + ") should have returned false",
FsDatasetTestUtil.breakHardlinksIfNeeded(fsd, b));
}
} finally {
client.close();
fs.close();
cluster.shutdown();
}
}
/**
* Test a simple flush on a simple HDFS file.
* @throws IOException an exception might be thrown

6
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetTestUtil.java
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@ -55,6 +55,12 @@ public class FsDatasetTestUtil {
.getGenerationStamp());
}
public static boolean breakHardlinksIfNeeded(FsDatasetSpi<?> fsd,
ExtendedBlock block) throws IOException {
final ReplicaInfo info = ((FsDatasetImpl)fsd).getReplicaInfo(block);
return info.breakHardLinksIfNeeded();
}
public static ReplicaInfo fetchReplicaInfo (final FsDatasetSpi<?> fsd,
final String bpid, final long blockId) {
return ((FsDatasetImpl)fsd).fetchReplicaInfo(bpid, blockId);