org.apache.hadoop.hdfs.server.namenode

Class EditsDoubleBuffer

java.lang.Object

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

@InterfaceAudience.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.

Constructor Summary

Constructors

Constructor and Description
EditsDoubleBuffer(int defaultBufferSize)

Method Summary

Methods

Modifier and Type	Method and 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)
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

Constructor Detail

EditsDoubleBuffer

public EditsDoubleBuffer(int defaultBufferSize)

Method Detail

writeOp

public void writeOp(FSEditLogOp op)
             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