org.apache.hadoop.hdfs

Class BlockReaderFactory

java.lang.Object

org.apache.hadoop.hdfs.BlockReaderFactory

@InterfaceAudience.Private
public class BlockReaderFactory
extends Object

Utility class to create BlockReader implementations.

Constructor Summary

Constructors

Constructor and Description
BlockReaderFactory()

Method Summary

Methods

Modifier and Type	Method and Description
static String	getFileName(InetSocketAddress s, String poolId, long blockId) File name to print when accessing a block directly (from servlets)
static BlockReader	newBlockReader(DFSClient.Conf conf, String file, ExtendedBlock block, Token<BlockTokenIdentifier> blockToken, long startOffset, long len, boolean verifyChecksum, String clientName, Peer peer, DatanodeID datanodeID, org.apache.hadoop.hdfs.DomainSocketFactory domSockFactory, org.apache.hadoop.hdfs.PeerCache peerCache, org.apache.hadoop.hdfs.FileInputStreamCache fisCache, boolean allowShortCircuitLocalReads, CachingStrategy cachingStrategy) Create a new BlockReader specifically to satisfy a read.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BlockReaderFactory

public BlockReaderFactory()

Method Detail

newBlockReader

public static BlockReader newBlockReader(DFSClient.Conf conf,
                         String file,
                         ExtendedBlock block,
                         Token<BlockTokenIdentifier> blockToken,
                         long startOffset,
                         long len,
                         boolean verifyChecksum,
                         String clientName,
                         Peer peer,
                         DatanodeID datanodeID,
                         org.apache.hadoop.hdfs.DomainSocketFactory domSockFactory,
                         org.apache.hadoop.hdfs.PeerCache peerCache,
                         org.apache.hadoop.hdfs.FileInputStreamCache fisCache,
                         boolean allowShortCircuitLocalReads,
                         CachingStrategy cachingStrategy)
                                  throws IOException

Create a new BlockReader specifically to satisfy a read. This method also sends the OP_READ_BLOCK request.

Parameters:

conf - the DFSClient configuration

file - File location

block - The block object

blockToken - The block token for security

startOffset - The read offset, relative to block head

len - The number of bytes to read, or -1 to read as many as possible.

bufferSize - The IO buffer size (not the client buffer size) Ignored except on the legacy BlockReader.

verifyChecksum - Whether to verify checksum

clientName - Client name. Used for log messages.

peer - The peer

datanodeID - The datanode that the Peer is connected to

domainSocketFactory - The DomainSocketFactory to notify if the Peer is a DomainPeer which turns out to be faulty. If null, no factory will be notified in this case.

allowShortCircuitLocalReads - True if short-circuit local reads should be allowed.

Returns:

New BlockReader instance

Throws:

IOException

getFileName

public static String getFileName(InetSocketAddress s,
                 String poolId,
                 long blockId)

File name to print when accessing a block directly (from servlets)

Parameters:

s - Address of the block location

poolId - Block pool ID of the block

blockId - Block ID of the block

Returns:

string that has a file name for debug purposes