alluxio.worker.block

Class UnderFileSystemBlockStore

java.lang.Object

alluxio.worker.block.UnderFileSystemBlockStore

All Implemented Interfaces:

SessionCleanable

public final class UnderFileSystemBlockStore
extends Object
implements SessionCleanable

This class manages the virtual blocks in the UFS for delegated UFS reads/writes. The usage pattern: acquireAccess(sessionId, blockId, options) closeReaderOrWriter(sessionId, blockId) releaseAccess(sessionId, blockId) If the client is lost before releasing or cleaning up the session, the session cleaner will clean the data.

Constructor Summary

Constructors

Constructor and Description
UnderFileSystemBlockStore(BlockStore localBlockStore, UfsManager ufsManager) Creates an instance of UnderFileSystemBlockStore.

Method Summary

Modifier and Type	Method and Description
boolean	acquireAccess(long sessionId, long blockId, Protocol.OpenUfsBlockOptions options) Acquires access for a UFS block given a UnderFileSystemBlockMeta and the limit on the maximum concurrency on the block.
void	cleanupSession(long sessionId) Cleans up all the block information(e.g.
void	closeReaderOrWriter(long sessionId, long blockId) Closes the block reader or writer and checks whether it is necessary to commit the block to Local block store.
BlockReader	getBlockReader(long sessionId, long blockId, long offset, boolean positionShort) Creates a block reader that reads from UFS and optionally caches the block to the Alluxio block store.
void	releaseAccess(long sessionId, long blockId) Releases the access token of this block by removing this (sessionId, blockId) pair from the store.

Methods inherited from class java.lang.Object

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

Constructor Detail

UnderFileSystemBlockStore

public UnderFileSystemBlockStore(BlockStore localBlockStore,
                                 UfsManager ufsManager)

Creates an instance of UnderFileSystemBlockStore.

Parameters:

localBlockStore - the local block store

ufsManager - the file manager

Method Detail

acquireAccess

public boolean acquireAccess(long sessionId,
                             long blockId,
                             Protocol.OpenUfsBlockOptions options)
                      throws BlockAlreadyExistsException

Acquires access for a UFS block given a UnderFileSystemBlockMeta and the limit on the maximum concurrency on the block. If the number of concurrent readers on this UFS block exceeds a threshold, the token is not granted and this method returns false.

Parameters:

sessionId - the session ID

blockId - maximum concurrency

options - the options

Returns:

whether an access token is acquired

Throws:

BlockAlreadyExistsException - if the block already exists for a session ID

closeReaderOrWriter

public void closeReaderOrWriter(long sessionId,
                                long blockId)
                         throws IOException

Closes the block reader or writer and checks whether it is necessary to commit the block to Local block store. During UFS block read, this is triggered when the block is unlocked. During UFS block write, this is triggered when the UFS block is committed.

Parameters:

sessionId - the session ID

blockId - the block ID

Throws:

IOException

releaseAccess

public void releaseAccess(long sessionId,
                          long blockId)

Releases the access token of this block by removing this (sessionId, blockId) pair from the store.

Parameters:

sessionId - the session ID

blockId - the block ID

cleanupSession

public void cleanupSession(long sessionId)

Cleans up all the block information(e.g. block reader/writer) that belongs to this session.

Specified by:

cleanupSession in interface SessionCleanable

Parameters:

sessionId - the session ID

getBlockReader

public BlockReader getBlockReader(long sessionId,
                                  long blockId,
                                  long offset,
                                  boolean positionShort)
                           throws BlockDoesNotExistException,
                                  IOException

Creates a block reader that reads from UFS and optionally caches the block to the Alluxio block store.

Parameters:

sessionId - the client session ID that requested this read

blockId - the ID of the block to read

offset - the read offset within the block (NOT the file)

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

Returns:

the block reader instance

Throws:

BlockDoesNotExistException - if the UFS block does not exist in the UnderFileSystemBlockStore

IOException