/**
* 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.DataTransferProtocol.Status.CHECKSUM_OK;
import static org.apache.hadoop.hdfs.protocol.DataTransferProtocol.Status.ERROR_ACCESS_TOKEN;
import static org.apache.hadoop.hdfs.protocol.DataTransferProtocol.Status.SUCCESS;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.nio.ByteBuffer;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.FSInputChecker;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.protocol.DataTransferProtocol;
import org.apache.hadoop.hdfs.security.BlockAccessToken;
import org.apache.hadoop.hdfs.security.InvalidAccessTokenException;
import org.apache.hadoop.hdfs.server.common.HdfsConstants;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.util.DataChecksum;
/** This is a wrapper around connection to datadone
* and understands checksum, offset etc
*/
@InterfaceAudience.Private
public class BlockReader extends FSInputChecker {
Socket dnSock; //for now just sending checksumOk.
private DataInputStream in;
private DataChecksum checksum;
/** offset in block of the last chunk received */
private long lastChunkOffset = -1;
private long lastChunkLen = -1;
private long lastSeqNo = -1;
/** offset in block where reader wants to actually read */
private long startOffset;
/** offset in block of of first chunk - may be less than startOffset
if startOffset is not chunk-aligned */
private final long firstChunkOffset;
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 final long bytesNeededToFinish;
private boolean gotEOS = false;
byte[] skipBuf = null;
ByteBuffer checksumBytes = null;
int dataLeft = 0;
/* FSInputChecker interface */
/* same interface as inputStream java.io.InputStream#read()
* used by DFSInputStream#read()
* This violates one rule when there is a checksum error:
* "Read should not modify user buffer before successful read"
* because it first reads the data to user buffer and then checks
* the checksum.
*/
@Override
public synchronized int read(byte[] buf, int off, int len)
throws IOException {
// This has to be set here, *before* the skip, since we can
// hit EOS during the skip, in the case that our entire read
// is smaller than the checksum chunk.
boolean eosBefore = gotEOS;
//for the first read, skip the extra bytes at the front.
if (lastChunkLen < 0 && startOffset > firstChunkOffset && len > 0) {
// Skip these bytes. But don't call this.skip()!
int toSkip = (int)(startOffset - firstChunkOffset);
if ( skipBuf == null ) {
skipBuf = new byte[bytesPerChecksum];
}
if ( super.read(skipBuf, 0, toSkip) != toSkip ) {
// should never happen
throw new IOException("Could not skip required number of bytes");
}
}
int nRead = super.read(buf, off, len);
// if gotEOS was set in the previous read and checksum is enabled :
if (gotEOS && !eosBefore && nRead >= 0 && needChecksum()) {
//checksum is verified and there are no errors.
checksumOk(dnSock);
}
return nRead;
}
@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;
}
@Override
public int read() throws IOException {
throw new IOException("read() is not expected to be invoked. " +
"Use read(buf, off, len) instead.");
}
@Override
public boolean seekToNewSource(long targetPos) throws IOException {
/* Checksum errors are handled outside the BlockReader.
* DFSInputStream does not always call 'seekToNewSource'. In the
* case of pread(), it just tries a different replica without seeking.
*/
return false;
}
@Override
public void seek(long pos) throws IOException {
throw new IOException("Seek() is not supported in BlockInputChecker");
}
@Override
protected long getChunkPosition(long pos) {
throw new RuntimeException("getChunkPosition() is not supported, " +
"since seek is not required");
}
/**
* Makes sure that checksumBytes has enough capacity
* and limit is set to the number of checksum bytes needed
* to be read.
*/
private void adjustChecksumBytes(int dataLen) {
int requiredSize =
((dataLen + bytesPerChecksum - 1)/bytesPerChecksum)*checksumSize;
if (checksumBytes == null || requiredSize > checksumBytes.capacity()) {
checksumBytes = ByteBuffer.wrap(new byte[requiredSize]);
} else {
checksumBytes.clear();
}
checksumBytes.limit(requiredSize);
}
@Override
protected synchronized int readChunk(long pos, byte[] buf, int offset,
int len, byte[] checksumBuf)
throws IOException {
// Read one chunk.
if ( gotEOS ) {
// Already hit EOF
return -1;
}
// Read one DATA_CHUNK.
long chunkOffset = lastChunkOffset;
if ( lastChunkLen > 0 ) {
chunkOffset += lastChunkLen;
}
// pos is relative to the start of the first chunk of the read.
// chunkOffset is relative to the start of the block.
// This makes sure that the read passed from FSInputChecker is the
// for the same chunk we expect to be reading from the DN.
if ( (pos + firstChunkOffset) != chunkOffset ) {
throw new IOException("Mismatch in pos : " + pos + " + " +
firstChunkOffset + " != " + chunkOffset);
}
// Read next packet if the previous packet has been read completely.
if (dataLeft <= 0) {
//Read packet headers.
int packetLen = in.readInt();
long offsetInBlock = in.readLong();
long seqno = in.readLong();
boolean lastPacketInBlock = in.readBoolean();
if (LOG.isDebugEnabled()) {
LOG.debug("DFSClient readChunk got seqno " + seqno +
" offsetInBlock " + offsetInBlock +
" lastPacketInBlock " + lastPacketInBlock +
" packetLen " + packetLen);
}
int dataLen = in.readInt();
// Sanity check the lengths
if ( ( dataLen <= 0 && !lastPacketInBlock ) ||
( dataLen != 0 && lastPacketInBlock) ||
(seqno != (lastSeqNo + 1)) ) {
throw new IOException("BlockReader: error in packet header" +
"(chunkOffset : " + chunkOffset +
", dataLen : " + dataLen +
", seqno : " + seqno +
" (last: " + lastSeqNo + "))");
}
lastSeqNo = seqno;
dataLeft = dataLen;
adjustChecksumBytes(dataLen);
if (dataLen > 0) {
IOUtils.readFully(in, checksumBytes.array(), 0,
checksumBytes.limit());
}
}
// Sanity checks
assert len >= bytesPerChecksum;
assert checksum != null;
assert checksumSize == 0 || (checksumBuf.length % checksumSize == 0);
int checksumsToRead, bytesToRead;
if (checksumSize > 0) {
// How many chunks left in our stream - this is a ceiling
// since we may have a partial chunk at the end of the file
int chunksLeft = (dataLeft - 1) / bytesPerChecksum + 1;
// How many chunks we can fit in databuffer
// - note this is a floor since we always read full chunks
int chunksCanFit = Math.min(len / bytesPerChecksum,
checksumBuf.length / checksumSize);
// How many chunks should we read
checksumsToRead = Math.min(chunksLeft, chunksCanFit);
// How many bytes should we actually read
bytesToRead = Math.min(
checksumsToRead * bytesPerChecksum, // full chunks
dataLeft); // in case we have a partial
} else {
// no checksum
bytesToRead = Math.min(dataLeft, len);
checksumsToRead = 0;
}
if ( bytesToRead > 0 ) {
// Assert we have enough space
assert bytesToRead <= len;
assert checksumBytes.remaining() >= checksumSize * checksumsToRead;
assert checksumBuf.length >= checksumSize * checksumsToRead;
IOUtils.readFully(in, buf, offset, bytesToRead);
checksumBytes.get(checksumBuf, 0, checksumSize * checksumsToRead);
}
dataLeft -= bytesToRead;
assert dataLeft >= 0;
lastChunkOffset = chunkOffset;
lastChunkLen = bytesToRead;
// If there's no data left in the current packet after satisfying
// this read, and we have satisfied the client read, we expect
// an empty packet header from the DN to signify this.
// Note that pos + bytesToRead may in fact be greater since the
// DN finishes off the entire last chunk.
if (dataLeft == 0 &&
pos + bytesToRead >= bytesNeededToFinish) {
// Read header
int packetLen = in.readInt();
long offsetInBlock = in.readLong();
long seqno = in.readLong();
boolean lastPacketInBlock = in.readBoolean();
int dataLen = in.readInt();
if (!lastPacketInBlock ||
dataLen != 0) {
throw new IOException("Expected empty end-of-read packet! Header: " +
"(packetLen : " + packetLen +
", offsetInBlock : " + offsetInBlock +
", seqno : " + seqno +
", lastInBlock : " + lastPacketInBlock +
", dataLen : " + dataLen);
}
gotEOS = true;
}
if ( bytesToRead == 0 ) {
return -1;
}
return bytesToRead;
}
private BlockReader( String file, long blockId, DataInputStream in,
DataChecksum checksum, boolean verifyChecksum,
long startOffset, long firstChunkOffset,
long bytesToRead,
Socket dnSock ) {
super(new Path("/blk_" + blockId + ":of:" + file)/*too non path-like?*/,
1, verifyChecksum,
checksum.getChecksumSize() > 0? checksum : null,
checksum.getBytesPerChecksum(),
checksum.getChecksumSize());
this.dnSock = dnSock;
this.in = in;
this.checksum = checksum;
this.startOffset = Math.max( startOffset, 0 );
// 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 ends mid-chunk.
this.bytesNeededToFinish = bytesToRead + (startOffset - firstChunkOffset);
this.firstChunkOffset = firstChunkOffset;
lastChunkOffset = firstChunkOffset;
lastChunkLen = -1;
bytesPerChecksum = this.checksum.getBytesPerChecksum();
checksumSize = this.checksum.getChecksumSize();
}
public static BlockReader newBlockReader(Socket sock, String file, long blockId, BlockAccessToken accessToken,
long genStamp, long startOffset, long len, int bufferSize) throws IOException {
return newBlockReader(sock, file, blockId, accessToken, genStamp, startOffset, len, bufferSize,
true);
}
/** Java Doc required */
public static BlockReader newBlockReader( Socket sock, String file, long blockId,
BlockAccessToken accessToken,
long genStamp,
long startOffset, long len,
int bufferSize, boolean verifyChecksum)
throws IOException {
return newBlockReader(sock, file, blockId, accessToken, genStamp, startOffset,
len, bufferSize, verifyChecksum, "");
}
public static BlockReader newBlockReader( Socket sock, String file,
long blockId,
BlockAccessToken accessToken,
long genStamp,
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)
DataTransferProtocol.Sender.opReadBlock(
new DataOutputStream(new BufferedOutputStream(
NetUtils.getOutputStream(sock,HdfsConstants.WRITE_TIMEOUT))),
blockId, genStamp, startOffset, len, clientName, accessToken);
//
// Get bytes in block, set streams
//
DataInputStream in = new DataInputStream(
new BufferedInputStream(NetUtils.getInputStream(sock),
bufferSize));
DataTransferProtocol.Status status = DataTransferProtocol.Status.read(in);
if (status != SUCCESS) {
if (status == ERROR_ACCESS_TOKEN) {
throw new InvalidAccessTokenException(
"Got access token error for OP_READ_BLOCK, self="
+ sock.getLocalSocketAddress() + ", remote="
+ sock.getRemoteSocketAddress() + ", for file " + file
+ ", for block " + blockId + "_" + genStamp);
} else {
throw new IOException("Got error for OP_READ_BLOCK, self="
+ sock.getLocalSocketAddress() + ", remote="
+ sock.getRemoteSocketAddress() + ", for file " + file
+ ", for block " + blockId + "_" + genStamp);
}
}
DataChecksum checksum = DataChecksum.newDataChecksum( in );
//Warning when we get CHECKSUM_NULL?
// Read the first chunk offset.
long firstChunkOffset = in.readLong();
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 BlockReader( file, blockId, in, checksum, verifyChecksum,
startOffset, firstChunkOffset, len,
sock );
}
@Override
public synchronized void close() throws IOException {
startOffset = -1;
checksum = null;
// in will be closed when its Socket is closed.
}
/** kind of like readFully(). Only reads as much as possible.
* And allows use of protected readFully().
*/
public int readAll(byte[] buf, int offset, int len) throws IOException {
return readFully(this, buf, offset, len);
}
/* When the reader reaches end of a block and there are no checksum
* errors, we send OP_STATUS_CHECKSUM_OK to datanode to inform that
* checksum was verified and there was no error.
*/
void checksumOk(Socket sock) {
try {
OutputStream out = NetUtils.getOutputStream(sock, HdfsConstants.WRITE_TIMEOUT);
CHECKSUM_OK.writeOutputStream(out);
out.flush();
} catch (IOException e) {
// its ok not to be able to send this.
LOG.debug("Could not write to datanode " + sock.getInetAddress() +
": " + e.getMessage());
}
}
}