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HDFS-14111. hdfsOpenFile on HDFS causes unnecessary IO from file offset 0. Contributed by Sahil Takiar.

Browse Source 
Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
This commit is contained in:
Sahil Takiar 2019-03-06 14:57:46 -08:00 committed by Wei-Chiu Chuang
parent 01ada40ea4
commit f5a4b43a49
8 changed files with 390 additions and 12 deletions
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1
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/CryptoInputStream.java
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@ -740,6 +740,7 @@ public boolean hasCapability(String capability) {
case StreamCapabilities.READAHEAD:
case StreamCapabilities.DROPBEHIND:
case StreamCapabilities.UNBUFFER:
case StreamCapabilities.READBYTEBUFFER:
return true;
default:
return false;

64
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/ByteBufferPositionedReadable.java Normal file
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@ -0,0 +1,64 @@
/**
* 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.fs;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* Implementers of this interface provide a positioned read API that writes to a
* {@link ByteBuffer} rather than a {@code byte[]}.
*
* @see PositionedReadable
* @see ByteBufferReadable
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface ByteBufferPositionedReadable {
/**
* Reads up to {@code buf.remaining()} bytes into buf from a given position
* in the file and returns the number of bytes read. Callers should use
* {@code buf.limit(...)} to control the size of the desired read and
* {@code buf.position(...)} to control the offset into the buffer the data
* should be written to.
* <p>
* After a successful call, {@code buf.position()} will be advanced by the
* number of bytes read and {@code buf.limit()} should be unchanged.
* <p>
* In the case of an exception, the values of {@code buf.position()} and
* {@code buf.limit()} are undefined, and callers should be prepared to
* recover from this eventuality.
* <p>
* Many implementations will throw {@link UnsupportedOperationException}, so
* callers that are not confident in support for this method from the
* underlying filesystem should be prepared to handle that exception.
* <p>
* Implementations should treat 0-length requests as legitimate, and must not
* signal an error upon their receipt.
*
* @param position position within file
* @param buf the ByteBuffer to receive the results of the read operation.
* @return the number of bytes read, possibly zero, or -1 if reached
* end-of-stream
* @throws IOException if there is some error performing the read
*/
int read(long position, ByteBuffer buf) throws IOException;
}

6
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/StreamCapabilities.java
View File

@ -59,6 +59,12 @@ public interface StreamCapabilities {
*/
String UNBUFFER = "in:unbuffer";
/**
* Stream read(ByteBuffer) capability implemented by
* {@link ByteBufferReadable#read(java.nio.ByteBuffer)}.
*/
String READBYTEBUFFER = "in:readbytebuffer";
/**
* Capabilities that a stream can support and be queried for.
*/

1
hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java
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@ -1779,6 +1779,7 @@ public boolean hasCapability(String capability) {
case StreamCapabilities.READAHEAD:
case StreamCapabilities.DROPBEHIND:
case StreamCapabilities.UNBUFFER:
case StreamCapabilities.READBYTEBUFFER:
return true;
default:
return false;

29
hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/hdfs.c
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@ -1013,7 +1013,7 @@ static hdfsFile hdfsOpenFileImpl(hdfsFS fs, const char *path, int flags,
return f{is|os};
*/
int accmode = flags & O_ACCMODE;
jstring jStrBufferSize = NULL, jStrReplication = NULL;
jstring jStrBufferSize = NULL, jStrReplication = NULL, jCapabilityString = NULL;
jobject jConfiguration = NULL, jPath = NULL, jFile = NULL;
jobject jFS = (jobject)fs;
jthrowable jthr;
@ -1171,16 +1171,22 @@ static hdfsFile hdfsOpenFileImpl(hdfsFS fs, const char *path, int flags,
file->flags = 0;
if ((flags & O_WRONLY) == 0) {
// Try a test read to see if we can do direct reads
char buf;
if (readDirect(fs, file, &buf, 0) == 0) {
// Success - 0-byte read should return 0
// Check the StreamCapabilities of jFile to see if we can do direct reads
jthr = newJavaStr(env, "in:readbytebuffer", &jCapabilityString);
if (jthr) {
ret = printExceptionAndFree(env, jthr, PRINT_EXC_ALL,
"hdfsOpenFile(%s): newJavaStr", path);
goto done;
}
jthr = invokeMethod(env, &jVal, INSTANCE, jFile, HADOOP_ISTRM,
"hasCapability", "(Ljava/lang/String;)Z", jCapabilityString);
if (jthr) {
ret = printExceptionAndFree(env, jthr, PRINT_EXC_ALL,
"hdfsOpenFile(%s): FSDataInputStream#hasCapability", path);
goto done;
}
if (jVal.z) {
file->flags |= HDFS_FILE_SUPPORTS_DIRECT_READ;
} else if (errno != ENOTSUP) {
// Unexpected error. Clear it, don't set the direct flag.
fprintf(stderr,
"hdfsOpenFile(%s): WARN: Unexpected error %d when testing "
"for direct read compatibility\n", path, errno);
}
}
ret = 0;
@ -1190,7 +1196,8 @@ done:
destroyLocalReference(env, jStrReplication);
destroyLocalReference(env, jConfiguration);
destroyLocalReference(env, jPath);
destroyLocalReference(env, jFile);
destroyLocalReference(env, jFile);
destroyLocalReference(env, jCapabilityString);
if (ret) {
if (file) {
if (file->file) {

5
hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/hdfs_ext_test.cc
View File

@ -503,7 +503,10 @@ TEST_F(HdfsExtTest, TestReadStats) {
hdfsFileFreeReadStatistics(stats);
EXPECT_EQ(0, hdfsCloseFile(fs, file));
EXPECT_EQ(0, errno);
// Since libhdfs is not guaranteed to set errno to 0 on successful
// operations, we disable this check for now, see HDFS-14325 for a
// long term solution to this problem
// EXPECT_EQ(0, errno);
}
//Testing working directory

27
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/AddBlockPoolException.java Normal file
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@ -0,0 +1,27 @@
package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
import java.io.IOException;
import java.util.Map;
import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
/**
* This exception collects all IOExceptions thrown when adding block pools and
* scanning volumes. It keeps the information about which volume is associated
* with an exception.
*
*/
public class AddBlockPoolException extends IOException {
private Map<FsVolumeSpi, IOException> unhealthyDataDirs;
public AddBlockPoolException(Map<FsVolumeSpi, IOException>
unhealthyDataDirs) {
this.unhealthyDataDirs = unhealthyDataDirs;
}
public Map<FsVolumeSpi, IOException> getFailingVolumes() {
return unhealthyDataDirs;
}
@Override
public String toString() {
return getClass().getName() + ": " + unhealthyDataDirs.toString();
}
}

269
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestByteBufferPread.java Normal file
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@ -0,0 +1,269 @@
/**
* 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.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Random;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
/**
* This class tests the DFS positional read functionality on a single node
* mini-cluster. These tests are inspired from {@link TestPread}. The tests
* are much less comprehensive than other pread tests because pread already
* internally uses {@link ByteBuffer}s.
*/
public class TestByteBufferPread {
private static MiniDFSCluster cluster;
private static FileSystem fs;
private static byte[] fileContents;
private static Path testFile;
private static Random rand;
private static final long SEED = 0xDEADBEEFL;
private static final int BLOCK_SIZE = 4096;
private static final int FILE_SIZE = 12 * BLOCK_SIZE;
@BeforeClass
public static void setup() throws IOException {
// Setup the cluster with a small block size so we can create small files
// that span multiple blocks
Configuration conf = new Configuration();
conf.setLong(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, BLOCK_SIZE);
cluster = new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
fs = cluster.getFileSystem();
// Create a test file that spans 12 blocks, and contains a bunch of random
// bytes
fileContents = new byte[FILE_SIZE];
rand = new Random(SEED);
rand.nextBytes(fileContents);
testFile = new Path("/byte-buffer-pread-test.dat");
try (FSDataOutputStream out = fs.create(testFile, (short) 3)) {
out.write(fileContents);
}
}
/**
* Test preads with {@link java.nio.HeapByteBuffer}s.
*/
@Test
public void testPreadWithHeapByteBuffer() throws IOException {
testPreadWithByteBuffer(ByteBuffer.allocate(FILE_SIZE));
testPreadWithFullByteBuffer(ByteBuffer.allocate(FILE_SIZE));
testPreadWithPositionedByteBuffer(ByteBuffer.allocate(FILE_SIZE));
testPreadWithLimitedByteBuffer(ByteBuffer.allocate(FILE_SIZE));
testPositionedPreadWithByteBuffer(ByteBuffer.allocate(FILE_SIZE));
}
/**
* Test preads with {@link java.nio.DirectByteBuffer}s.
*/
@Test
public void testPreadWithDirectByteBuffer() throws IOException {
testPreadWithByteBuffer(ByteBuffer.allocateDirect(FILE_SIZE));
testPreadWithFullByteBuffer(ByteBuffer.allocateDirect(FILE_SIZE));
testPreadWithPositionedByteBuffer(ByteBuffer.allocateDirect(FILE_SIZE));
testPreadWithLimitedByteBuffer(ByteBuffer.allocateDirect(FILE_SIZE));
testPositionedPreadWithByteBuffer(ByteBuffer.allocateDirect(FILE_SIZE));
}
/**
* Reads the entire testFile using the pread API and validates that its
* contents are properly loaded into the supplied {@link ByteBuffer}.
*/
private void testPreadWithByteBuffer(ByteBuffer buffer) throws IOException {
int bytesRead;
int totalBytesRead = 0;
try (FSDataInputStream in = fs.open(testFile)) {
while ((bytesRead = in.read(totalBytesRead, buffer)) > 0) {
totalBytesRead += bytesRead;
// Check that each call to read changes the position of the ByteBuffer
// correctly
assertEquals(totalBytesRead, buffer.position());
}
// Make sure the buffer is full
assertFalse(buffer.hasRemaining());
// Make sure the contents of the read buffer equal the contents of the
// file
buffer.position(0);
byte[] bufferContents = new byte[FILE_SIZE];
buffer.get(bufferContents);
assertArrayEquals(bufferContents, fileContents);
buffer.position(buffer.limit());
}
}
/**
* Attempts to read the testFile into a {@link ByteBuffer} that is already
* full, and validates that doing so does not change the contents of the
* supplied {@link ByteBuffer}.
*/
private void testPreadWithFullByteBuffer(ByteBuffer buffer)
throws IOException {
// Load some dummy data into the buffer
byte[] existingBufferBytes = new byte[FILE_SIZE];
rand.nextBytes(existingBufferBytes);
buffer.put(existingBufferBytes);
// Make sure the buffer is full
assertFalse(buffer.hasRemaining());
try (FSDataInputStream in = fs.open(testFile)) {
// Attempt to read into the buffer, 0 bytes should be read since the
// buffer is full
assertEquals(0, in.read(buffer));
// Double check the buffer is still full and its contents have not
// changed
assertFalse(buffer.hasRemaining());
buffer.position(0);
byte[] bufferContents = new byte[FILE_SIZE];
buffer.get(bufferContents);
assertArrayEquals(bufferContents, existingBufferBytes);
}
}
/**
* Reads half of the testFile into the {@link ByteBuffer} by setting a
* {@link ByteBuffer#limit} on the buffer. Validates that only half of the
* testFile is loaded into the buffer.
*/
private void testPreadWithLimitedByteBuffer(
ByteBuffer buffer) throws IOException {
int bytesRead;
int totalBytesRead = 0;
// Set the buffer limit to half the size of the file
buffer.limit(FILE_SIZE / 2);
try (FSDataInputStream in = fs.open(testFile)) {
while ((bytesRead = in.read(totalBytesRead, buffer)) > 0) {
totalBytesRead += bytesRead;
// Check that each call to read changes the position of the ByteBuffer
// correctly
assertEquals(totalBytesRead, buffer.position());
}
// Since we set the buffer limit to half the size of the file, we should
// have only read half of the file into the buffer
assertEquals(totalBytesRead, FILE_SIZE / 2);
// Check that the buffer is full and the contents equal the first half of
// the file
assertFalse(buffer.hasRemaining());
buffer.position(0);
byte[] bufferContents = new byte[FILE_SIZE / 2];
buffer.get(bufferContents);
assertArrayEquals(bufferContents,
Arrays.copyOfRange(fileContents, 0, FILE_SIZE / 2));
}
}
/**
* Reads half of the testFile into the {@link ByteBuffer} by setting the
* {@link ByteBuffer#position} the half the size of the file. Validates that
* only half of the testFile is loaded into the buffer.
*/
private void testPreadWithPositionedByteBuffer(
ByteBuffer buffer) throws IOException {
int bytesRead;
int totalBytesRead = 0;
// Set the buffer position to half the size of the file
buffer.position(FILE_SIZE / 2);
try (FSDataInputStream in = fs.open(testFile)) {
while ((bytesRead = in.read(totalBytesRead, buffer)) > 0) {
totalBytesRead += bytesRead;
// Check that each call to read changes the position of the ByteBuffer
// correctly
assertEquals(totalBytesRead + FILE_SIZE / 2, buffer.position());
}
// Since we set the buffer position to half the size of the file, we
// should have only read half of the file into the buffer
assertEquals(totalBytesRead, FILE_SIZE / 2);
// Check that the buffer is full and the contents equal the first half of
// the file
assertFalse(buffer.hasRemaining());
buffer.position(FILE_SIZE / 2);
byte[] bufferContents = new byte[FILE_SIZE / 2];
buffer.get(bufferContents);
assertArrayEquals(bufferContents,
Arrays.copyOfRange(fileContents, 0, FILE_SIZE / 2));
}
}
/**
* Reads half of the testFile into the {@link ByteBuffer} by specifying a
* position for the pread API that is half of the file size. Validates that
* only half of the testFile is loaded into the buffer.
*/
private void testPositionedPreadWithByteBuffer(
ByteBuffer buffer) throws IOException {
int bytesRead;
int totalBytesRead = 0;
try (FSDataInputStream in = fs.open(testFile)) {
// Start reading from halfway through the file
while ((bytesRead = in.read(totalBytesRead + FILE_SIZE / 2,
buffer)) > 0) {
totalBytesRead += bytesRead;
// Check that each call to read changes the position of the ByteBuffer
// correctly
assertEquals(totalBytesRead, buffer.position());
}
// Since we starting reading halfway through the file, the buffer should
// only be half full
assertEquals(totalBytesRead, FILE_SIZE / 2);
assertEquals(buffer.position(), FILE_SIZE / 2);
assertTrue(buffer.hasRemaining());
// Check that the buffer contents equal the second half of the file
buffer.position(0);
byte[] bufferContents = new byte[FILE_SIZE / 2];
buffer.get(bufferContents);
assertArrayEquals(bufferContents,
Arrays.copyOfRange(fileContents, FILE_SIZE / 2, FILE_SIZE));
}
}
@AfterClass
public static void shutdown() throws IOException {
try {
fs.delete(testFile, false);
fs.close();
} finally {
cluster.shutdown(true);
}
}
}