com.bigdata.journal

Class DiskOnlyStrategy

java.lang.Object

com.bigdata.rawstore.AbstractRawStore

com.bigdata.rawstore.AbstractRawWormStore

com.bigdata.journal.AbstractBufferStrategy

com.bigdata.journal.DiskOnlyStrategy

All Implemented Interfaces:

ICounterSetAccess, IBufferStrategy, IDiskBasedStrategy, IAddressManager, IMRMW, IMROW, IRawStore, IStreamStore, IWORM

Deprecated.

This has been replaced by WORMStrategy.

public class DiskOnlyStrategy
extends AbstractBufferStrategy
implements IDiskBasedStrategy

Disk-based journal strategy.

Writes are buffered in a write cache. The cache is flushed when it would overflow. As a result only large sequential writes are performed on the store. Reads read through the write cache for consistency.

Note: This is used to realize both the BufferMode.Disk and the BufferMode.Temporary BufferModes. When configured for the BufferMode.Temporary mode: the root blocks will not be written onto the disk, writes will not be forced, and the backing file will be created the first time the DiskOnlyStrategy attempts to write through to the disk. For many scenarios, the backing file will never be created unless the write cache overflows. This provides very low latency on start-up, the same MRMW capability, and allows very large temporary stores. FIXME Examine behavior when write caching is enabled/disabled for the OS. This has a profound impact. Asynchronous writes of multiple buffers, and the use of smaller buffers, may be absolutely when the write cache is disabled. It may be that swapping sets in because the Windows write cache is being overworked, in which case doing incremental and async IO would help. Compare with behavior on server platforms. See http://support.microsoft.com/kb/259716, http://www.accucadd.com/TechNotes/Cache/WriteBehindCache.htm, http://msdn2.microsoft.com/en-us/library/aa365165.aspx, http://www.jasonbrome.com/blog/archives/2004/04/03/writecache_enabled.html, http://support.microsoft.com/kb/811392, http://mail-archives.apache.org/mod_mbox/db-derby-dev/200609.mbox/%3C44F820A8.6000000@sun.com%3E

                /sbin/hdparm -W 0 /dev/hda 0 Disable write caching
                /sbin/hdparm -W 1 /dev/hda 1 Enable write caching
 

Version:

$Id$

Author:

Bryan Thompson

See Also:

BufferMode.Disk, BufferMode.Temporary

Field Summary

Fields inherited from class com.bigdata.journal.AbstractBufferStrategy

bufferMode, commitOffset, ERR_ADDRESS_IS_NULL, ERR_ADDRESS_NOT_WRITTEN, ERR_BAD_RECORD_SIZE, ERR_BUFFER_EMPTY, ERR_BUFFER_NULL, ERR_BUFFER_OVERRUN, ERR_MAX_EXTENT, ERR_NOT_OPEN, ERR_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 interface com.bigdata.rawstore.IAddressManager

NULL

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Deprecated. Closes the file immediately (without flushing any pending writes).
void	closeForWrites() Deprecated. Extended to discard the write cache.
void	commit() Deprecated. Need to override commit to ensure the writeCache is flushed prior to writing the root block.
void	delete(long addr) Deprecated. The default is a NOP.
void	deleteResources() Deprecated. Deletes the backing file(s) (if any).
void	force(boolean metadata) Deprecated. flushes the writeCache before syncing the disk.
FileChannel	getChannel() Deprecated. Note: This MAY be null.
CounterSet	getCounters() Deprecated. Return interesting information about the write cache and file operations.
long	getExtent() Deprecated. The current size of the journal in bytes.
File	getFile() Deprecated. The backing file.
int	getHeaderSize() Deprecated. The size of the file header in bytes.
RandomAccessFile	getRandomAccessFile() Deprecated. Note: This MAY be null.
WORMStrategy.StoreCounters	getStoreCounters() Deprecated. Returns the performance counters for the store.
long	getUserExtent() Deprecated. The size of the user data extent in bytes.
boolean	isFullyBuffered() Deprecated. True iff the store is fully buffered (all reads are against memory).
boolean	isStable() Deprecated. True iff backed by stable storage.
ByteBuffer	read(long addr) Deprecated. Note: ClosedChannelException and AsynchronousCloseException can get thrown out of this method (wrapped as RuntimeExceptions) if a reader task is interrupted.
ByteBuffer	readRootBlock(boolean rootBlock0) Deprecated. Read the specified root block from the backing file.
void	setCommitRecordIndex(CommitRecordIndex commitRecordIndex) Deprecated.
void	setNextOffset(long lastOffset) Deprecated.
void	setStoreCounters(WORMStrategy.StoreCounters storeCounters) Deprecated. Replaces the WORMStrategy.StoreCounters object.
long	transferTo(RandomAccessFile out) Deprecated. A block operation that transfers the serialized records (aka the written on portion of the user extent) en mass from the buffer onto an output file.
void	truncate(long newExtent) Deprecated. Either truncates or extends the journal.
long	write(ByteBuffer data) Deprecated. Write the data (unisolated).
void	writeRootBlock(IRootBlockView rootBlock, ForceEnum forceOnCommit) Deprecated. Write the root block onto stable storage (ie, flush it through to disk).

Methods inherited from class com.bigdata.journal.AbstractBufferStrategy

abort, assertOpen, destroy, getBufferMode, getInitialExtent, getMaximumExtent, getMaxRecordSize, getMetaBitsAddr, getMetaStartAddr, getMinimumExtension, getNextOffset, getResourceMetadata, getUUID, isDirty, isOpen, isReadOnly, overflow, requiresCommit, size, transferFromDiskTo, useChecksums

Methods inherited from class com.bigdata.rawstore.AbstractRawWormStore

getAddressManager, getByteCount, getOffset, getOffsetBits, getPhysicalAddress, toAddr, toString

Methods inherited from class com.bigdata.rawstore.AbstractRawStore

getInputStream, getOutputStream

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

abort, getAddressManager, getBufferMode, getInitialExtent, getMaximumExtent, getMaxRecordSize, getMetaBitsAddr, getMetaStartAddr, getNextOffset, getOffsetBits, isDirty, requiresCommit, useChecksums

Methods inherited from interface com.bigdata.rawstore.IRawStore

destroy, getResourceMetadata, getUUID, isOpen, isReadOnly, size

Methods inherited from interface com.bigdata.rawstore.IAddressManager

getByteCount, getOffset, getPhysicalAddress, toAddr, toString

Methods inherited from interface com.bigdata.rawstore.IStreamStore

getInputStream, getOutputStream

Method Detail

commit

public void commit()

Deprecated.

Need to override commit to ensure the writeCache is flushed prior to writing the root block. For the DiskOnlyStrategy flushing the writeCache also ensures the backing file is created if the file is temporary. Note that the internal call to flush the writeCache must be synchronized or concurrent writers to the cache will cause problems.

Specified by:

commit in interface IBufferStrategy

Overrides:

commit in class AbstractBufferStrategy

getHeaderSize

public final int getHeaderSize()

Deprecated.

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()

Deprecated.

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()

Deprecated.

Note: This MAY be null. If BufferMode.Temporary is used then it WILL be null until the writeCache is flushed to disk for the first time.

Specified by:

getRandomAccessFile in interface IDiskBasedStrategy

getChannel

public final FileChannel getChannel()

Deprecated.

Note: This MAY be null. If BufferMode.Temporary is used then it WILL be null until the writeCache is flushed to disk for the first time.

Specified by:

getChannel in interface IDiskBasedStrategy

getStoreCounters

public WORMStrategy.StoreCounters getStoreCounters()

Deprecated.

Returns the performance counters for the store.

setStoreCounters

public void setStoreCounters(WORMStrategy.StoreCounters storeCounters)

Deprecated.

Replaces the WORMStrategy.StoreCounters object.

Parameters:

storeCounters - The new BTree.Counters.

Throws:

IllegalArgumentException - if the argument is null.

getCounters

public CounterSet getCounters()

Deprecated.

Return interesting information about the write cache and file operations.

Specified by:

getCounters in interface ICounterSetAccess

Specified by:

getCounters in interface IBufferStrategy

isStable

public final boolean isStable()

Deprecated.

Description copied from interface: IRawStore

True iff backed by stable storage.

Specified by:

isStable in interface IRawStore

isFullyBuffered

public boolean isFullyBuffered()

Deprecated.

Description copied from interface: IRawStore

True iff the store is fully buffered (all reads are against memory). Implementations MAY change the value returned by this method over the life cycle of the store, e.g., to conserve memory a store may drop or decrease its buffer if it is backed by disk.

Note: This does not guarantee that the OS will not swap the buffer onto disk.

Specified by:

isFullyBuffered in interface IRawStore

force

public void force(boolean metadata)

Deprecated.

flushes the writeCache before syncing the 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()

Deprecated.

Closes the file immediately (without flushing any pending writes).

Specified by:

close in interface IRawStore

Overrides:

close in class AbstractBufferStrategy

deleteResources

public void deleteResources()

Deprecated.

Description copied from interface: IRawStore

Deletes the backing file(s) (if any).

Specified by:

deleteResources in interface IRawStore

getExtent

public final long getExtent()

Deprecated.

Description copied from interface: IBufferStrategy

The current size of the journal in bytes. When the journal is backed by a disk file this is the actual size on disk of that file. The initial value for this property is set by Options.INITIAL_EXTENT.

Specified by:

getExtent in interface IBufferStrategy

getUserExtent

public final long getUserExtent()

Deprecated.

Description copied from interface: IBufferStrategy

The size of the user data extent in bytes.

Note: The size of the user extent is always generally smaller than the value reported by IBufferStrategy.getExtent() since the latter also reports the space allocated to the journal header and root blocks.

Specified by:

getUserExtent in interface IBufferStrategy

read

public ByteBuffer read(long addr)

Deprecated.

Note: ClosedChannelException and AsynchronousCloseException can get thrown out of this method (wrapped as RuntimeExceptions) if a reader task is interrupted.

Specified by:

read in interface IRawStore

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).

write

public long write(ByteBuffer data)

Deprecated.

Description copied from interface: IRawStore

Write the data (unisolated).

Specified by:

write in interface IRawStore

Parameters:

data - The data. The bytes from the current Buffer.position() to the Buffer.limit() will be written and the Buffer.position() will be advanced to the Buffer.limit() . The caller may subsequently modify the contents of the buffer without changing the state of the store (i.e., the data are copied into the store).

Returns:

A long integer formed that encodes both the offset from which the data may be read and the #of bytes to be read. See IAddressManager.

readRootBlock

public ByteBuffer readRootBlock(boolean rootBlock0)

Deprecated.

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)

Deprecated.

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().

truncate

public void truncate(long newExtent)

Deprecated.

Description copied from interface: IBufferStrategy

Either truncates or extends the journal.

Note: Implementations of this method MUST be synchronized so that the operation is atomic with respect to concurrent writers.

Specified by:

truncate in interface IBufferStrategy

Parameters:

newExtent - The new extent of the journal. This value represent the total extent of the journal, including any root blocks together with the user extent.

transferTo

public long transferTo(RandomAccessFile out)
                throws IOException

Deprecated.

Description copied from interface: IBufferStrategy

A block operation that transfers the serialized records (aka the written on portion of the user extent) en mass from the buffer onto an output file. The buffered records are written "in order" starting at the current position on the output file. The file is grown if necessary. The file position is advanced to the last byte written on the file.

Note: Implementations of this method MUST be synchronized so that the operation is atomic with respect to concurrent writers.

Specified by:

transferTo in interface IBufferStrategy

Parameters:

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

Returns:

The #of bytes written.

Throws:

IOException

closeForWrites

public void closeForWrites()

Deprecated.

Extended to discard the write cache.

Note: The file is NOT closed and re-opened in a read-only mode in order to avoid causing difficulties for concurrent readers.

Specified by:

closeForWrites in interface IBufferStrategy

Overrides:

closeForWrites in class AbstractBufferStrategy

delete

public void delete(long addr)

Deprecated.

Description copied from class: AbstractBufferStrategy

The default is a NOP.

Specified by:

delete in interface IRawStore

Overrides:

delete in class AbstractBufferStrategy

Parameters:

addr - A long integer formed using Addr that encodes both the offset at which the data was written and the #of bytes that were written.

setNextOffset

public void setNextOffset(long lastOffset)

Deprecated.

setCommitRecordIndex

public void setCommitRecordIndex(CommitRecordIndex commitRecordIndex)

Deprecated.