Package org.apache.hadoop.io.erasurecode.coder

Class HHXORErasureDecoder

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.hadoop.io.erasurecode.coder.ErasureDecoder

org.apache.hadoop.io.erasurecode.coder.HHXORErasureDecoder

All Implemented Interfaces:

Configurable, ErasureCoder

@Private
public class HHXORErasureDecoder
extends ErasureDecoder

Hitchhiker is a new erasure coding algorithm developed as a research project at UC Berkeley by Rashmi Vinayak. It has been shown to reduce network traffic and disk I/O by 25%-45% during data reconstruction while retaining the same storage capacity and failure tolerance capability of RS codes. The Hitchhiker algorithm is described in K.V.Rashmi, et al., "A "Hitchhiker's" Guide to Fast and Efficient Data Reconstruction in Erasure-coded Data Centers", in ACM SIGCOMM 2014. This is Hitchhiker-XOR erasure decoder that decodes a block group.

Constructor Summary

Constructors

Constructor	Description
HHXORErasureDecoder(ErasureCoderOptions options)

Method Summary

Modifier and Type	Method	Description
boolean	preferDirectBuffer()	Tell if direct or off-heap buffer is preferred or not.
protected ErasureCodingStep	prepareDecodingStep(ECBlockGroup blockGroup)	Perform decoding against a block blockGroup.
void	release()	Release the resources if any.

Methods inherited from class org.apache.hadoop.io.erasurecode.coder.ErasureDecoder

calculateCoding, getErasedIndexes, getInputBlocks, getNumDataUnits, getNumErasedBlocks, getNumErasedBlocks, getNumParityUnits, getOptions, getOutputBlocks

Methods inherited from class org.apache.hadoop.conf.Configured

getConf, setConf

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Constructor Details

HHXORErasureDecoder

public HHXORErasureDecoder(ErasureCoderOptions options)

Method Details

prepareDecodingStep

protected ErasureCodingStep prepareDecodingStep(ECBlockGroup blockGroup)

Description copied from class: ErasureDecoder

Perform decoding against a block blockGroup.

Specified by:

prepareDecodingStep in class ErasureDecoder

Parameters:

blockGroup - blockGroup.

Returns:

decoding step for caller to do the real work

preferDirectBuffer

public boolean preferDirectBuffer()

Description copied from interface: ErasureCoder

Tell if direct or off-heap buffer is preferred or not. It's for callers to decide how to allocate coding chunk buffers, either on heap or off heap. It will return false by default.

Specified by:

preferDirectBuffer in interface ErasureCoder

Overrides:

preferDirectBuffer in class ErasureDecoder

Returns:

true if direct buffer is preferred for performance consideration, otherwise false.

release

public void release()

Description copied from interface: ErasureCoder

Release the resources if any. Good chance to invoke RawErasureCoder#release.

Specified by:

release in interface ErasureCoder

Overrides:

release in class ErasureDecoder