org.apache.hadoop.hdfs

Class ReplicaAccessor

java.lang.Object

org.apache.hadoop.hdfs.ReplicaAccessor

@InterfaceAudience.Public
 @InterfaceStability.Stable
public abstract class ReplicaAccessor
extends Object

The public API for ReplicaAccessor objects.

Constructor Summary

Constructors

Constructor and Description
ReplicaAccessor()

Method Summary

Modifier and Type	Method and Description
abstract void	close() Release the resources associated with the ReplicaAccessor.
int	getNetworkDistance() Return the network distance between local machine and the remote machine.
abstract boolean	isLocal() Return true if bytes read via this accessor should count towards the local byte count statistics.
abstract boolean	isShortCircuit() Return true if bytes read via this accessor should count towards the short-circuit byte count statistics.
abstract int	read(long pos, byte[] buf, int off, int len) Read bytes from the replica.
abstract int	read(long pos, ByteBuffer buf) Read bytes from the replica.

Methods inherited from class java.lang.Object

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

Constructor Detail

ReplicaAccessor

public ReplicaAccessor()

Method Detail

read

public abstract int read(long pos,
                         byte[] buf,
                         int off,
                         int len)
                  throws IOException

Read bytes from the replica.

Parameters:

pos - The position in the replica to start reading at. Must not be negative.

buf - The byte array to read into.

off - The offset within buf to start reading into.

len - The maximum length to read.

Returns:

The number of bytes read. If the read extends past the end of the replica, a short read count will be returned. We will should return -1 if EOF is reached and no bytes can be returned. We will never return a short read count unless EOF is reached.

Throws:

IOException

read

public abstract int read(long pos,
                         ByteBuffer buf)
                  throws IOException

Read bytes from the replica.

Parameters:

pos - The position in the replica to start reading at. Must not be negative.

buf - The byte buffer to read into. The amount to read will be dictated by the remaining bytes between the current position and the limit. The ByteBuffer may or may not be direct.

Returns:

The number of bytes read. If the read extends past the end of the replica, a short read count will be returned. We should return -1 if EOF is reached and no bytes can be returned. We will never return a short read count unless EOF is reached.

Throws:

IOException

close

public abstract void close()
                    throws IOException

Release the resources associated with the ReplicaAccessor. It is recommended that implementations never throw an IOException. The method is declared as throwing IOException in order to remain compatible with java.io.Closeable. If an exception is thrown, the ReplicaAccessor must still be closed when the function returns in order to prevent a resource leak.

Throws:

IOException

isLocal

public abstract boolean isLocal()

Return true if bytes read via this accessor should count towards the local byte count statistics.

isShortCircuit

public abstract boolean isShortCircuit()

Return true if bytes read via this accessor should count towards the short-circuit byte count statistics.

getNetworkDistance

public int getNetworkDistance()

Return the network distance between local machine and the remote machine.