alluxio.client.file

Class FileSystemContext

java.lang.Object

alluxio.client.file.FileSystemContext

All Implemented Interfaces:

Closeable, AutoCloseable

@ThreadSafe
public final class FileSystemContext
extends Object
implements Closeable

A shared context that isolates all operations within a FileSystem. Usually, one user only needs one instance of FileSystemContext.

NOTE: The context maintains a pool of file system master clients that is already thread-safe. Synchronizing FileSystemContext methods could lead to deadlock: thread A attempts to acquire a client when there are no clients left in the pool and blocks holding a lock on the FileSystemContext, when thread B attempts to release a client it owns it is unable to do so, because thread A holds the lock on FileSystemContext.

Method Summary

Modifier and Type	Method and Description
CloseableResource<BlockMasterClient>	acquireBlockMasterClientResource() Acquires a block master client resource from the block master client pool.
FileSystemMasterClient	acquireMasterClient() Acquires a file system master client from the file system master client pool.
CloseableResource<FileSystemMasterClient>	acquireMasterClientResource() Acquires a file system master client from the file system master client pool.
io.netty.channel.Channel	acquireNettyChannel(WorkerNetAddress workerNetAddress) Acquires a netty channel from the channel pools.
static void	clearCache() Clears the context cache.
void	close() Closes all the resources associated with the context.
static FileSystemContext	create(Subject subject, MasterInquireClient masterInquireClient) This method is provided for testing, use the get() methods.
static FileSystemContext	get()
static FileSystemContext	get(Subject subject)
WorkerNetAddress	getLocalWorker()
InetSocketAddress	getMasterAddress()
MasterInquireClient	getMasterInquireClient()
Subject	getParentSubject()
boolean	hasLocalWorker()
void	releaseMasterClient(FileSystemMasterClient masterClient) Releases a file system master client into the file system master client pool.
void	releaseNettyChannel(WorkerNetAddress workerNetAddress, io.netty.channel.Channel channel) Releases a netty channel to the channel pools.
void	reset(InstancedConfiguration configuration) Resets the context.

Methods inherited from class java.lang.Object

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

Method Detail

get

public static FileSystemContext get()

Returns:

the instance of file system context with no subject associated

get

public static FileSystemContext get(Subject subject)

Parameters:

subject - the subject associated with this context

Returns:

the instance of the file system context, possibly a shared context

create

public static FileSystemContext create(Subject subject,
                                       MasterInquireClient masterInquireClient)

This method is provided for testing, use the get() methods. The returned context object will not be cached automatically.

Parameters:

subject - the parent subject, set to null if not present

masterInquireClient - the client to use for determining the master; note that if the context is reset, this client will be replaced with a new masterInquireClient based on global configuration

Returns:

the context

clearCache

public static void clearCache()

Clears the context cache. This method should only be called in test code.

close

public void close()
           throws IOException

Closes all the resources associated with the context. Make sure all the resources are released back to this context before calling this close. After closing the context, all the resources that acquired from this context might fail. Only call this when you are done with using the FileSystem associated with this FileSystemContext.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

reset

public void reset(InstancedConfiguration configuration)
           throws IOException

Resets the context. It is only used in AbstractFileSystem and tests to reset the default file system context.

Parameters:

configuration - the instance configuration

Throws:

IOException

getParentSubject

public Subject getParentSubject()

Returns:

the parent subject

getMasterAddress

public InetSocketAddress getMasterAddress()
                                   throws UnavailableException

Returns:

the master address

Throws:

UnavailableException - if the master address cannot be determined

getMasterInquireClient

public MasterInquireClient getMasterInquireClient()

Returns:

the master inquire client

acquireMasterClient

public FileSystemMasterClient acquireMasterClient()

Acquires a file system master client from the file system master client pool.

Returns:

the acquired file system master client

releaseMasterClient

public void releaseMasterClient(FileSystemMasterClient masterClient)

Releases a file system master client into the file system master client pool.

Parameters:

masterClient - a file system master client to release

acquireMasterClientResource

public CloseableResource<FileSystemMasterClient> acquireMasterClientResource()

Acquires a file system master client from the file system master client pool. The resource is Closeable.

Returns:

the acquired file system master client resource

acquireBlockMasterClientResource

public CloseableResource<BlockMasterClient> acquireBlockMasterClientResource()

Acquires a block master client resource from the block master client pool. The resource is Closeable.

Returns:

the acquired block master client resource

acquireNettyChannel

public io.netty.channel.Channel acquireNettyChannel(WorkerNetAddress workerNetAddress)
                                             throws IOException

Acquires a netty channel from the channel pools. If there is no available client instance available in the pool, it tries to create a new one. And an exception is thrown if it fails to create a new one.

Parameters:

workerNetAddress - the network address of the channel

Returns:

the acquired netty channel

Throws:

IOException

releaseNettyChannel

public void releaseNettyChannel(WorkerNetAddress workerNetAddress,
                                io.netty.channel.Channel channel)

Releases a netty channel to the channel pools.

Parameters:

workerNetAddress - the address of the channel

channel - the channel to release

hasLocalWorker

public boolean hasLocalWorker()
                       throws IOException

Returns:

if there is a local worker running the same machine

Throws:

IOException

getLocalWorker

public WorkerNetAddress getLocalWorker()
                                throws IOException

Returns:

a local worker running the same machine, or null if none is found

Throws:

IOException