alluxio.worker.block

Class UnderFileSystemBlockReader

java.lang.Object

alluxio.worker.block.UnderFileSystemBlockReader

All Implemented Interfaces:

BlockReader, Closeable, AutoCloseable

@NotThreadSafe
public final class UnderFileSystemBlockReader
extends Object
implements BlockReader

This class implements a BlockReader to read a block directly from UFS, and optionally cache the block to the Alluxio worker if the whole block it is read.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the block reader.
static UnderFileSystemBlockReader	create(UnderFileSystemBlockMeta blockMeta, long offset, boolean positionShort, BlockStore localBlockStore, UfsManager ufsManager, UfsInputStreamManager ufsInstreamManager) Creates an instance of UnderFileSystemBlockReader and initializes it with a reading offset.
ReadableByteChannel	getChannel() Returns a readable byte channel of the block.
long	getLength() Gets the length of the block in bytes.
AlluxioURI	getUfsMountPointUri()
boolean	isClosed()
ByteBuffer	read(long offset, long length) Reads data from the block.
int	transferTo(io.netty.buffer.ByteBuf buf) This interface is supposed to be used for sequence block reads.

Methods inherited from class java.lang.Object

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

Method Detail

create

public static UnderFileSystemBlockReader create(UnderFileSystemBlockMeta blockMeta,
                                                long offset,
                                                boolean positionShort,
                                                BlockStore localBlockStore,
                                                UfsManager ufsManager,
                                                UfsInputStreamManager ufsInstreamManager)
                                         throws IOException

Creates an instance of UnderFileSystemBlockReader and initializes it with a reading offset.

Parameters:

blockMeta - the block meta

offset - the position within the block to start the read

localBlockStore - the Local block store

ufsManager - the manager of ufs

ufsInstreamManager - the manager of ufs instreams

positionShort - whether the client op is a positioned read to a small buffer

Returns:

the block reader

Throws:

IOException

getChannel

public ReadableByteChannel getChannel()

Description copied from interface: BlockReader

Returns a readable byte channel of the block.

Specified by:

getChannel in interface BlockReader

Returns:

channel

getLength

public long getLength()

Description copied from interface: BlockReader

Gets the length of the block in bytes.

Specified by:

getLength in interface BlockReader

Returns:

the length of the block in bytes

read

public ByteBuffer read(long offset,
                       long length)
                throws IOException

Description copied from interface: BlockReader

Reads data from the block.

Specified by:

read in interface BlockReader

Parameters:

offset - the offset from starting of the block file in bytes

length - the length of data to read in bytes, -1 for the rest of the block

Returns:

ByteBuffer the data that was read

Throws:

IOException

transferTo

public int transferTo(io.netty.buffer.ByteBuf buf)
               throws IOException

This interface is supposed to be used for sequence block reads.

Specified by:

transferTo in interface BlockReader

Parameters:

buf - the byte buffer

Returns:

the number of bytes read, -1 if it reaches EOF and none was read

Throws:

IOException

close

public void close()
           throws IOException

Closes the block reader. After this, this block reader should not be used anymore. This is recommended to be called after the client finishes reading the block. It is usually triggered when the client unlocks the block.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

isClosed

public boolean isClosed()

Specified by:

isClosed in interface BlockReader

Returns:

true if this reader is closed

getUfsMountPointUri

public AlluxioURI getUfsMountPointUri()

Returns:

the mount point URI of the UFS that this reader is currently reading from