/**
* 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 static org.apache.hadoop.hdfs.protocol.HdfsProtoUtil.vintPrefixed;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.ChecksumException;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil;
import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
import org.apache.hadoop.hdfs.protocol.datatransfer.Sender;
import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.BlockOpResponseProto;
import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ClientReadStatusProto;
import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ReadOpChecksumInfoProto;
import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
import org.apache.hadoop.hdfs.util.DirectBufferPool;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.net.SocketInputStream;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.util.DataChecksum;
import com.google.common.base.Preconditions;
/**
* This is a wrapper around connection to datanode
* and understands checksum, offset etc.
*
* Terminology:
* <dl>
* <dt>block</dt>
* <dd>The hdfs block, typically large (~64MB).
* </dd>
* <dt>chunk</dt>
* <dd>A block is divided into chunks, each comes with a checksum.
* We want transfers to be chunk-aligned, to be able to
* verify checksums.
* </dd>
* <dt>packet</dt>
* <dd>A grouping of chunks used for transport. It contains a
* header, followed by checksum data, followed by real data.
* </dd>
* </dl>
* Please see DataNode for the RPC specification.
*
* This is a new implementation introduced in Hadoop 0.23 which
* is more efficient and simpler than the older BlockReader
* implementation. It should be renamed to RemoteBlockReader
* once we are confident in it.
*/
@InterfaceAudience.Private
public class RemoteBlockReader2 implements BlockReader {
static final Log LOG = LogFactory.getLog(RemoteBlockReader2.class);
Socket dnSock; //for now just sending the status code (e.g. checksumOk) after the read.
private ReadableByteChannel in;
private DataChecksum checksum;
private PacketHeader curHeader;
private ByteBuffer curPacketBuf = null;
private ByteBuffer curDataSlice = null;
/** offset in block of the last chunk received */
private long lastSeqNo = -1;
/** offset in block where reader wants to actually read */
private long startOffset;
private final String filename;
private static DirectBufferPool bufferPool = new DirectBufferPool();
private ByteBuffer headerBuf = ByteBuffer.allocate(
PacketHeader.PKT_HEADER_LEN);
private int bytesPerChecksum;
private int checksumSize;
/**
* The total number of bytes we need to transfer from the DN.
* This is the amount that the user has requested plus some padding
* at the beginning so that the read can begin on a chunk boundary.
*/
private long bytesNeededToFinish;
private final boolean verifyChecksum;
private boolean sentStatusCode = false;
byte[] skipBuf = null;
ByteBuffer checksumBytes = null;
/** Amount of unread data in the current received packet */
int dataLeft = 0;
@Override
public synchronized int read(byte[] buf, int off, int len)
throws IOException {
if (curPacketBuf == null || curDataSlice.remaining() == 0 && bytesNeededToFinish > 0) {
readNextPacket();
}
if (curDataSlice.remaining() == 0) {
// we're at EOF now
return -1;
}
int nRead = Math.min(curDataSlice.remaining(), len);
curDataSlice.get(buf, off, nRead);
return nRead;
}
private void readNextPacket() throws IOException {
Preconditions.checkState(curHeader == null || !curHeader.isLastPacketInBlock());
//Read packet headers.
readPacketHeader();
if (LOG.isTraceEnabled()) {
LOG.trace("DFSClient readNextPacket got header " + curHeader);
}
// Sanity check the lengths
if (!curHeader.sanityCheck(lastSeqNo)) {
throw new IOException("BlockReader: error in packet header " +
curHeader);
}
if (curHeader.getDataLen() > 0) {
int chunks = 1 + (curHeader.getDataLen() - 1) / bytesPerChecksum;
int checksumsLen = chunks * checksumSize;
int bufsize = checksumsLen + curHeader.getDataLen();
resetPacketBuffer(checksumsLen, curHeader.getDataLen());
lastSeqNo = curHeader.getSeqno();
if (bufsize > 0) {
readChannelFully(in, curPacketBuf);
curPacketBuf.flip();
if (verifyChecksum) {
verifyPacketChecksums();
}
}
bytesNeededToFinish -= curHeader.getDataLen();
}
// First packet will include some data prior to the first byte
// the user requested. Skip it.
if (curHeader.getOffsetInBlock() < startOffset) {
int newPos = (int) (startOffset - curHeader.getOffsetInBlock());
curDataSlice.position(newPos);
}
// If we've now satisfied the whole client read, read one last packet
// header, which should be empty
if (bytesNeededToFinish <= 0) {
readTrailingEmptyPacket();
if (verifyChecksum) {
sendReadResult(dnSock, Status.CHECKSUM_OK);
} else {
sendReadResult(dnSock, Status.SUCCESS);
}
}
}
private void verifyPacketChecksums() throws ChecksumException {
// N.B.: the checksum error offset reported here is actually
// relative to the start of the block, not the start of the file.
// This is slightly misleading, but preserves the behavior from
// the older BlockReader.
checksum.verifyChunkedSums(curDataSlice, curPacketBuf,
filename, curHeader.getOffsetInBlock());
}
private static void readChannelFully(ReadableByteChannel ch, ByteBuffer buf)
throws IOException {
while (buf.remaining() > 0) {
int n = ch.read(buf);
if (n < 0) {
throw new IOException("Premature EOF reading from " + ch);
}
}
}
private void resetPacketBuffer(int checksumsLen, int dataLen) {
int packetLen = checksumsLen + dataLen;
if (curPacketBuf == null ||
curPacketBuf.capacity() < packetLen) {
returnPacketBufToPool();
curPacketBuf = bufferPool.getBuffer(packetLen);
}
curPacketBuf.position(checksumsLen);
curDataSlice = curPacketBuf.slice();
curDataSlice.limit(dataLen);
curPacketBuf.clear();
curPacketBuf.limit(checksumsLen + dataLen);
}
@Override
public synchronized long skip(long n) throws IOException {
/* How can we make sure we don't throw a ChecksumException, at least
* in majority of the cases?. This one throws. */
if ( skipBuf == null ) {
skipBuf = new byte[bytesPerChecksum];
}
long nSkipped = 0;
while ( nSkipped < n ) {
int toSkip = (int)Math.min(n-nSkipped, skipBuf.length);
int ret = read(skipBuf, 0, toSkip);
if ( ret <= 0 ) {
return nSkipped;
}
nSkipped += ret;
}
return nSkipped;
}
private void readPacketHeader() throws IOException {
headerBuf.clear();
readChannelFully(in, headerBuf);
headerBuf.flip();
if (curHeader == null) curHeader = new PacketHeader();
curHeader.readFields(headerBuf);
}
private void readTrailingEmptyPacket() throws IOException {
if (LOG.isTraceEnabled()) {
LOG.trace("Reading empty packet at end of read");
}
headerBuf.clear();
readChannelFully(in, headerBuf);
headerBuf.flip();
PacketHeader trailer = new PacketHeader();
trailer.readFields(headerBuf);
if (!trailer.isLastPacketInBlock() ||
trailer.getDataLen() != 0) {
throw new IOException("Expected empty end-of-read packet! Header: " +
trailer);
}
}
protected RemoteBlockReader2(String file, String bpid, long blockId,
ReadableByteChannel in, DataChecksum checksum, boolean verifyChecksum,
long startOffset, long firstChunkOffset, long bytesToRead, Socket dnSock) {
// Path is used only for printing block and file information in debug
this.dnSock = dnSock;
this.in = in;
this.checksum = checksum;
this.verifyChecksum = verifyChecksum;
this.startOffset = Math.max( startOffset, 0 );
this.filename = file;
// The total number of bytes that we need to transfer from the DN is
// the amount that the user wants (bytesToRead), plus the padding at
// the beginning in order to chunk-align. Note that the DN may elect
// to send more than this amount if the read starts/ends mid-chunk.
this.bytesNeededToFinish = bytesToRead + (startOffset - firstChunkOffset);
bytesPerChecksum = this.checksum.getBytesPerChecksum();
checksumSize = this.checksum.getChecksumSize();
}
@Override
public synchronized void close() throws IOException {
returnPacketBufToPool();
startOffset = -1;
checksum = null;
if (dnSock != null) {
dnSock.close();
}
// in will be closed when its Socket is closed.
}
@Override
protected void finalize() throws Throwable {
try {
// just in case it didn't get closed, we
// may as well still try to return the buffer
returnPacketBufToPool();
} finally {
super.finalize();
}
}
private void returnPacketBufToPool() {
if (curPacketBuf != null) {
bufferPool.returnBuffer(curPacketBuf);
curPacketBuf = null;
}
}
/**
* Take the socket used to talk to the DN.
*/
public Socket takeSocket() {
assert hasSentStatusCode() :
"BlockReader shouldn't give back sockets mid-read";
Socket res = dnSock;
dnSock = null;
return res;
}
/**
* Whether the BlockReader has reached the end of its input stream
* and successfully sent a status code back to the datanode.
*/
public boolean hasSentStatusCode() {
return sentStatusCode;
}
/**
* When the reader reaches end of the read, it sends a status response
* (e.g. CHECKSUM_OK) to the DN. Failure to do so could lead to the DN
* closing our connection (which we will re-open), but won't affect
* data correctness.
*/
void sendReadResult(Socket sock, Status statusCode) {
assert !sentStatusCode : "already sent status code to " + sock;
try {
writeReadResult(sock, statusCode);
sentStatusCode = true;
} catch (IOException e) {
// It's ok not to be able to send this. But something is probably wrong.
LOG.info("Could not send read status (" + statusCode + ") to datanode " +
sock.getInetAddress() + ": " + e.getMessage());
}
}
/**
* Serialize the actual read result on the wire.
*/
static void writeReadResult(Socket sock, Status statusCode)
throws IOException {
OutputStream out = NetUtils.getOutputStream(sock, HdfsServerConstants.WRITE_TIMEOUT);
ClientReadStatusProto.newBuilder()
.setStatus(statusCode)
.build()
.writeDelimitedTo(out);
out.flush();
}
/**
* File name to print when accessing a block directly (from servlets)
* @param s Address of the block location
* @param poolId Block pool ID of the block
* @param blockId Block ID of the block
* @return string that has a file name for debug purposes
*/
public static String getFileName(final InetSocketAddress s,
final String poolId, final long blockId) {
return s.toString() + ":" + poolId + ":" + blockId;
}
@Override
public int readAll(byte[] buf, int offset, int len) throws IOException {
return BlockReaderUtil.readAll(this, buf, offset, len);
}
@Override
public void readFully(byte[] buf, int off, int len) throws IOException {
BlockReaderUtil.readFully(this, buf, off, len);
}
/**
* Create a new BlockReader specifically to satisfy a read.
* This method also sends the OP_READ_BLOCK request.
*
* @param sock An established Socket to the DN. The BlockReader will not close it normally.
* This socket must have an associated Channel.
* @param file File location
* @param block The block object
* @param blockToken The block token for security
* @param startOffset The read offset, relative to block head
* @param len The number of bytes to read
* @param bufferSize The IO buffer size (not the client buffer size)
* @param verifyChecksum Whether to verify checksum
* @param clientName Client name
* @return New BlockReader instance, or null on error.
*/
public static BlockReader newBlockReader( Socket sock, String file,
ExtendedBlock block,
Token<BlockTokenIdentifier> blockToken,
long startOffset, long len,
int bufferSize, boolean verifyChecksum,
String clientName)
throws IOException {
// in and out will be closed when sock is closed (by the caller)
final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
NetUtils.getOutputStream(sock,
HdfsServerConstants.WRITE_TIMEOUT)));
new Sender(out).readBlock(block, blockToken, clientName, startOffset, len);
//
// Get bytes in block, set streams
//
Preconditions.checkArgument(sock.getChannel() != null,
"Socket %s does not have an associated Channel.",
sock);
SocketInputStream sin =
(SocketInputStream)NetUtils.getInputStream(sock);
DataInputStream in = new DataInputStream(sin);
BlockOpResponseProto status = BlockOpResponseProto.parseFrom(
vintPrefixed(in));
checkSuccess(status, sock, block, file);
ReadOpChecksumInfoProto checksumInfo =
status.getReadOpChecksumInfo();
DataChecksum checksum = DataTransferProtoUtil.fromProto(
checksumInfo.getChecksum());
//Warning when we get CHECKSUM_NULL?
// Read the first chunk offset.
long firstChunkOffset = checksumInfo.getChunkOffset();
if ( firstChunkOffset < 0 || firstChunkOffset > startOffset ||
firstChunkOffset >= (startOffset + checksum.getBytesPerChecksum())) {
throw new IOException("BlockReader: error in first chunk offset (" +
firstChunkOffset + ") startOffset is " +
startOffset + " for file " + file);
}
return new RemoteBlockReader2(file, block.getBlockPoolId(), block.getBlockId(),
sin, checksum, verifyChecksum, startOffset, firstChunkOffset, len, sock);
}
static void checkSuccess(
BlockOpResponseProto status, Socket sock,
ExtendedBlock block, String file)
throws IOException {
if (status.getStatus() != Status.SUCCESS) {
if (status.getStatus() == Status.ERROR_ACCESS_TOKEN) {
throw new InvalidBlockTokenException(
"Got access token error for OP_READ_BLOCK, self="
+ sock.getLocalSocketAddress() + ", remote="
+ sock.getRemoteSocketAddress() + ", for file " + file
+ ", for pool " + block.getBlockPoolId() + " block "
+ block.getBlockId() + "_" + block.getGenerationStamp());
} else {
throw new IOException("Got error for OP_READ_BLOCK, self="
+ sock.getLocalSocketAddress() + ", remote="
+ sock.getRemoteSocketAddress() + ", for file " + file
+ ", for pool " + block.getBlockPoolId() + " block "
+ block.getBlockId() + "_" + block.getGenerationStamp());
}
}
}
}