com.bigdata.journal
Class DirectBufferStrategy

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

All Implemented Interfaces:

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

public class DirectBufferStrategy
extends DiskBackedBufferStrategy

Direct buffer strategy uses a direct ByteBuffer as a write through cache and writes through to disk for persistence.

Version:

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

Author:

Bryan Thompson

See Also:

BufferMode.Direct

TODO:

modify to support aio (asynchronous io). aio can be supported with a 2nd thread that writes behind from the cache to the file. force() will need to be modified to wait until the aio thread has caught up to the nextOffset (i.e., has written all data that is dirty on the buffer).

Field Summary

Fields inherited from class com.bigdata.journal.DiskBackedBufferStrategy

opener

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

boolean	isFullyBuffered() True iff the store is fully buffered (all reads are against memory).
void	truncate(long newExtent) Note: This is synchronized since it MAY be invoked directly while concurrent writers are running and not just from AbstractBufferStrategy.overflow(long).
long	write(ByteBuffer data) Extends the basic behavior to write through to the backing file.

Methods inherited from class com.bigdata.journal.DiskBackedBufferStrategy

close, deleteResources, force, getChannel, getFile, getHeaderSize, getRandomAccessFile, isStable, read, readRootBlock, transferTo, writeRootBlock

Methods inherited from class com.bigdata.journal.BasicBufferStrategy

getBufferView, getCounters, getExtent, getUserExtent

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

Methods inherited from interface com.bigdata.rawstore.IRawStore

destroy, getResourceMetadata, getUUID, isOpen, isReadOnly, size

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

Method Detail

isFullyBuffered

public boolean isFullyBuffered()

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.

write

public long write(ByteBuffer data)

Extends the basic behavior to write through to the backing file.

Note: ClosedChannelException can be thrown out of this method. This exception is an indication that the backing channel was closed while a writer was still running.

Note: ClosedByInterruptException can be thrown out of this method (wrapped as a RuntimeException). This exception is an indication that a writer was interrupted. This will occur if you are using ExecutorService.shutdownNow() on a service that is running one or more writers. In such cases this should not be considered an error but the expected result of interrupting the writer.

However, note that ClosedByInterruptException means that the channel was actually closed when the writer was interrupted. This means that you basically can not interrupt running writers without having to re-open the channel.

Specified by:

write in interface IRawStore

Overrides:

write in class BasicBufferStrategy

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.

truncate

public void truncate(long newExtent)

Description copied from class: BasicBufferStrategy

Note: This is synchronized since it MAY be invoked directly while concurrent writers are running and not just from AbstractBufferStrategy.overflow(long).

Specified by:

truncate in interface IBufferStrategy

Overrides:

truncate in class BasicBufferStrategy

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.