Package org.apache.hadoop.hdfs.server.namenode

Class EditsDoubleBuffer

java.lang.Object

org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer

@Private
public class EditsDoubleBuffer
extends Object

A double-buffer for edits. New edits are written into the first buffer while the second is available to be flushed. Each time the double-buffer is flushed, the two internal buffers are swapped. This allows edits to progress concurrently to flushes without allocating new buffers each time.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor	Description
EditsDoubleBuffer(int defaultBufferSize)

Method Summary

Modifier and Type	Method	Description
void	close()
int	countBufferedBytes()
int	countReadyBytes()
int	countReadyTxns()
void	flushTo(OutputStream out)	Writes the content of the "ready" buffer to the given output stream, and resets it.
long	getFirstReadyTxId()
boolean	isFlushed()
void	setReadyToFlush()
boolean	shouldForceSync()
void	writeOp(FSEditLogOp op, int logVersion)
void	writeRaw(byte[] bytes, int offset, int length)

Methods inherited from class java.lang.Object

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

Field Details

LOG

protected static final org.slf4j.Logger LOG

Constructor Details

EditsDoubleBuffer

public EditsDoubleBuffer(int defaultBufferSize)

Method Details

writeOp

public void writeOp(FSEditLogOp op,
 int logVersion)
             throws IOException

Throws:

IOException

writeRaw

public void writeRaw(byte[] bytes,
 int offset,
 int length)
              throws IOException

Throws:

IOException

close

public void close()
           throws IOException

Throws:

IOException

setReadyToFlush

public void setReadyToFlush()

flushTo

public void flushTo(OutputStream out)
             throws IOException

Writes the content of the "ready" buffer to the given output stream, and resets it. Does not swap any buffers.

Throws:

IOException

shouldForceSync

public boolean shouldForceSync()

isFlushed

public boolean isFlushed()

countBufferedBytes

public int countBufferedBytes()

getFirstReadyTxId

public long getFirstReadyTxId()

Returns:

the transaction ID of the first transaction ready to be flushed

countReadyTxns

public int countReadyTxns()

Returns:

the number of transactions that are ready to be flushed

countReadyBytes

public int countReadyBytes()

Returns:

the number of bytes that are ready to be flushed