com.bigdata.journal
Class DiskBackedBufferStrategy

java.lang.Object
  com.bigdata.rawstore.AbstractRawStore
      com.bigdata.rawstore.AbstractRawWormStore
          com.bigdata.journal.AbstractBufferStrategy
              com.bigdata.journal.BasicBufferStrategy
                  com.bigdata.journal.DiskBackedBufferStrategy

All Implemented Interfaces:

IBufferStrategy, IDiskBasedStrategy, IAddressManager, IMRMW, IMROW, IRawStore, IStoreSerializer, IWORM

Direct Known Subclasses:

DirectBufferStrategy, MappedBufferStrategy

public abstract class DiskBackedBufferStrategy
extends BasicBufferStrategy
implements IDiskBasedStrategy

Abstract base class for implementations that use a direct buffer as a write through cache to an image on the disk. This covers both the BufferMode.Direct, where we use explicit IO operations, and the BufferMode.Mapped, where we memory-map the image. Common features shared by these implementations deal mainly with initialization of a new disk image.

Version:

$Id: DiskBackedBufferStrategy.java 2265 2009-10-26 12:51:06Z thompsonbry $

Author:

Bryan Thompson

TODO:

write tests of the disk-only mode operations when overflowing an int32 extent., consider a read buffer that uses a weak value cache backed by an LRU hard reference cache, which in turn evicts buffers back to a pool for reuse. The pool would bin buffers by size, keep no more than some #of buffers of a given size, and offer a service to allocate buffers of no less than a given capacity. This might reduce heap churn by recycling buffers in addition to providing minimizing the need to hit the OS disk cache, the disk buffers, or the disk platter.

Field Summary

protected IReopenChannel

opener Used to re-open the FileChannel in this class.

Fields inherited from class com.bigdata.journal.BasicBufferStrategy

extent, userExtent

Fields inherited from class com.bigdata.journal.AbstractBufferStrategy

bufferMode, ERR_ADDRESS_IS_NULL, ERR_ADDRESS_NOT_WRITTEN, ERR_BAD_RECORD_SIZE, ERR_BUFFER_EMPTY, ERR_BUFFER_NULL, ERR_INT32, ERR_NOT_OPEN, ERR_READ_ONLY, ERR_RECORD_LENGTH_ZERO, ERR_TRUNCATE, initialExtent, log, maximumExtent, nextOffset, WARN

Fields inherited from class com.bigdata.rawstore.AbstractRawWormStore

am

Fields inherited from class com.bigdata.rawstore.AbstractRawStore

serializer

Fields inherited from interface com.bigdata.rawstore.IAddressManager

NULL

Method Summary

void	close() Closes the file.
void	deleteResources() Deletes the backing file(s) (if any) and clears any records for the store from the IGlobalLRU.
void	force(boolean metadata) Forces the data to disk.
FileChannel	getChannel() The channel used to read and write on the file.
File	getFile() The backing file.
int	getHeaderSize() The size of the file header in bytes.
RandomAccessFile	getRandomAccessFile() The object used to read and write on that file.
boolean	isStable() True iff backed by stable storage.
ByteBuffer	read(long addr) The backing file is fully buffered so it does not need to be open for a read to succeed.
ByteBuffer	readRootBlock(boolean rootBlock0) Read the specified root block from the backing file.
long	transferTo(RandomAccessFile out) Note: This is synchronized so that concurrent writers must block during this operation.
void	writeRootBlock(IRootBlockView rootBlock, ForceEnum forceOnCommit) Write the root block onto stable storage (ie, flush it through to disk).

Methods inherited from class com.bigdata.journal.BasicBufferStrategy

getBufferView, getCounters, getExtent, getUserExtent, truncate, write

Methods inherited from class com.bigdata.journal.AbstractBufferStrategy

assertOpen, closeForWrites, destroy, getBufferMode, getInitialExtent, getMaximumExtent, getNextOffset, getResourceMetadata, getUUID, isOpen, isReadOnly, overflow, size, transferFromDiskTo

Methods inherited from class com.bigdata.rawstore.AbstractRawWormStore

getAddressManager, getByteCount, getOffset, getOffsetBits, packAddr, toAddr, toString, unpackAddr

Methods inherited from class com.bigdata.rawstore.AbstractRawStore

deserialize, deserialize, deserialize, serialize

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.bigdata.journal.IBufferStrategy

closeForWrites, getBufferMode, getCounters, getExtent, getInitialExtent, getMaximumExtent, getNextOffset, getUserExtent, truncate

Methods inherited from interface com.bigdata.rawstore.IRawStore

destroy, getResourceMetadata, getUUID, isFullyBuffered, isOpen, isReadOnly, size, write

Methods inherited from interface com.bigdata.rawstore.IAddressManager

getByteCount, getOffset, packAddr, toAddr, toString, unpackAddr

Methods inherited from interface com.bigdata.rawstore.IStoreSerializer

deserialize, deserialize, deserialize, serialize

Field Detail

opener

protected final IReopenChannel opener

Used to re-open the FileChannel in this class.

Method Detail

getHeaderSize

public final int getHeaderSize()

Description copied from interface: IDiskBasedStrategy

The size of the file header in bytes.

Specified by:

getHeaderSize in interface IBufferStrategy

Specified by:

getHeaderSize in interface IDiskBasedStrategy

getFile

public final File getFile()

Description copied from interface: IDiskBasedStrategy

The backing file.

Specified by:

getFile in interface IDiskBasedStrategy

Specified by:

getFile in interface IRawStore

getRandomAccessFile

public final RandomAccessFile getRandomAccessFile()

Description copied from interface: IDiskBasedStrategy

The object used to read and write on that file.

Specified by:

getRandomAccessFile in interface IDiskBasedStrategy

getChannel

public final FileChannel getChannel()

Description copied from interface: IDiskBasedStrategy

The channel used to read and write on the file.

Specified by:

getChannel in interface IDiskBasedStrategy

isStable

public final boolean isStable()

Description copied from interface: IRawStore

True iff backed by stable storage.

Specified by:

isStable in interface IRawStore

force

public void force(boolean metadata)

Forces the data to disk.

Specified by:

force in interface IRawStore

Parameters:

metadata - If true, then force both the file contents and the file metadata to disk.

close

public void close()

Closes the file.

Specified by:

close in interface IRawStore

Overrides:

close in class BasicBufferStrategy

deleteResources

public void deleteResources()

Description copied from interface: IRawStore

Deletes the backing file(s) (if any) and clears any records for the store from the IGlobalLRU.

Specified by:

deleteResources in interface IRawStore

readRootBlock

public ByteBuffer readRootBlock(boolean rootBlock0)

Description copied from interface: IBufferStrategy

Read the specified root block from the backing file.

Specified by:

readRootBlock in interface IBufferStrategy

writeRootBlock

public void writeRootBlock(IRootBlockView rootBlock,
                           ForceEnum forceOnCommit)

Description copied from interface: IBufferStrategy

Write the root block onto stable storage (ie, flush it through to disk).

Specified by:

writeRootBlock in interface IBufferStrategy

Parameters:

rootBlock - The root block. Which root block is indicated by IRootBlockView.isRootBlock0().

transferTo

public long transferTo(RandomAccessFile out)
                throws IOException

Description copied from class: BasicBufferStrategy

Note: This is synchronized so that concurrent writers must block during this operation.

Specified by:

transferTo in interface IBufferStrategy

Overrides:

transferTo in class BasicBufferStrategy

Parameters:

out - The file to which the buffer contents will be transferred.

Returns:

The #of bytes written.

Throws:

IOException

read

public ByteBuffer read(long addr)

The backing file is fully buffered so it does not need to be open for a read to succeed. However, we use this as an opportunity to transparently re-open the FileChannel if it has been closed asynchronously or in response to an interrupt (that is, if we discover that the channel is closed but AbstractBufferStrategy.isOpen() still returns true).

Specified by:

read in interface IRawStore

Overrides:

read in class BasicBufferStrategy

Parameters:

addr - A long integer that encodes both the offset from which the data will be read and the #of bytes to be read. See IAddressManager.toAddr(int, long).

Returns:

The data read. The buffer will be flipped to prepare for reading (the position will be zero and the limit will be the #of bytes read).