org.apache.flink.runtime.io.disk.iomanager

Class ChannelAccess<T,R extends org.apache.flink.runtime.io.disk.iomanager.IORequest>

java.lang.Object

org.apache.flink.runtime.io.disk.iomanager.ChannelAccess<T,R>

Type Parameters:

T - The buffer type used for the underlying IO operations.

Direct Known Subclasses:

BlockChannelAccess

public abstract class ChannelAccess<T,R extends org.apache.flink.runtime.io.disk.iomanager.IORequest>
extends Object

A base class for readers and writers that read data from I/O manager channels, or write data to them. Requests handled by channels that inherit from this class are executed asynchronously, which allows write-behind for writers and pre-fetching for readers.

Field Summary

Fields

Modifier and Type	Field and Description
protected IOException	exception An exception that was encountered by the asynchronous request handling thread.
protected FileChannel	fileChannel A file channel for NIO access to the file.
protected Channel.ID	id The ID of the underlying channel.
protected RequestQueue<R>	requestQueue A request queue for submitting asynchronous requests to the corresponding IO worker thread.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ChannelAccess(Channel.ID channelID, RequestQueue<R> requestQueue, boolean writeEnabled) Creates a new channel to the path indicated by the given ID.

Method Summary

Modifier and Type	Method and Description
void	checkErroneous() Checks the exception state of this channel.
void	deleteChannel() Deletes this channel by physically removing the file beneath it.
Channel.ID	getChannelID() Gets the channel ID of this channel.
abstract boolean	isClosed() Checks, whether this channel has been closed;
protected abstract void	returnBuffer(T buffer) This method is invoked by the asynchronous I/O thread to return a buffer after the I/O request completed.

Methods inherited from class java.lang.Object

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

Field Detail

id

protected final Channel.ID id

The ID of the underlying channel.

fileChannel

protected final FileChannel fileChannel

A file channel for NIO access to the file.

requestQueue

protected final RequestQueue<R extends org.apache.flink.runtime.io.disk.iomanager.IORequest> requestQueue

A request queue for submitting asynchronous requests to the corresponding IO worker thread.

exception

protected volatile IOException exception

An exception that was encountered by the asynchronous request handling thread.

Constructor Detail

ChannelAccess

protected ChannelAccess(Channel.ID channelID,
                        RequestQueue<R> requestQueue,
                        boolean writeEnabled)
                 throws IOException

Creates a new channel to the path indicated by the given ID. The channel hands IO requests to the given request queue to be processed.

Parameters:

channelID - The id describing the path of the file that the channel accessed.

requestQueue - The queue that this channel hands its IO requests to.

writeEnabled - Flag describing whether the channel should be opened in read/write mode, rather than in read-only mode.

Throws:

IOException - Thrown, if the channel could no be opened.

Method Detail

isClosed

public abstract boolean isClosed()

Checks, whether this channel has been closed;

Returns:

True, if the channel has been closed, false otherwise.

returnBuffer

protected abstract void returnBuffer(T buffer)

This method is invoked by the asynchronous I/O thread to return a buffer after the I/O request completed.

Parameters:

buffer - The buffer to be returned.

getChannelID

public final Channel.ID getChannelID()

Gets the channel ID of this channel.

Returns:

This channel's ID.

checkErroneous

public final void checkErroneous()
                          throws IOException

Checks the exception state of this channel. The channel is erroneous, if one of its requests could not be processed correctly.

Throws:

IOException - Thrown, if the channel is erroneous. The thrown exception contains the original exception that defined the erroneous state as its cause.

deleteChannel

public void deleteChannel()

Deletes this channel by physically removing the file beneath it. This method may only be called on a closed channel.