IBufferStrategy (bigdata®)

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com.bigdata.journal
Interface IBufferStrategy

All Superinterfaces:: IAddressManager, IMRMW, IMROW, IRawStore, IStoreSerializer

All Known Subinterfaces:: IDiskBasedStrategy

All Known Implementing Classes:: AbstractBufferStrategy, BasicBufferStrategy, BufferedDiskStrategy, DirectBufferStrategy, DiskBackedBufferStrategy, DiskOnlyStrategy, MappedBufferStrategy, TransientBufferStrategy

public interface IBufferStrategy
extends IRawStore, IMRMW
extends IRawStore, IMRMW

Interface for implementations of a buffer strategy as identified by a BufferMode. This interface is designed to encapsulate the specifics of reading and writing slots and performing operations to make an atomic commit.

Version:: $Id: IBufferStrategy.java 2265 2009-10-26 12:51:06Z thompsonbry $
Author:: Bryan Thompson

Field Summary

Fields inherited from interface com.bigdata.rawstore.IAddressManager
`NULL`

Method Summary
`void`	`closeForWrites()` Seals the store against further writes and discards any write caches since they will no longer be used.
`BufferMode`	`getBufferMode()` The buffer mode supported by the implementation
`CounterSet`	`getCounters()` Return the performance counter hierarchy.
`long`	`getExtent()` The current size of the journal in bytes.
`int`	`getHeaderSize()` The size of the journal header, including MAGIC, version, and both root blocks.
`long`	`getInitialExtent()` The initial extent.
`long`	`getMaximumExtent()` The maximum extent allowable before a buffer overflow operation will be rejected.
`long`	`getNextOffset()` The next offset at which a data item would be written on the store as an offset into the user extent.
`long`	`getUserExtent()` The size of the user data extent in bytes.
`ByteBuffer`	`readRootBlock(boolean rootBlock0)` Read the specified root block from the backing file.
`long`	`transferTo(RandomAccessFile out)` 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 extent)` Either truncates or extends the journal.
`void`	`writeRootBlock(IRootBlockView rootBlock, ForceEnum forceOnCommitEnum)` Write the root block onto stable storage (ie, flush it through to disk).

Methods inherited from interface com.bigdata.rawstore.IRawStore
`close, deleteResources, destroy, force, getFile, getResourceMetadata, getUUID, isFullyBuffered, isOpen, isReadOnly, isStable, read, 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`

Method Detail

getNextOffset

long getNextOffset()

The next offset at which a data item would be written on the store as an offset into the user extent.

getBufferMode

BufferMode getBufferMode()

The buffer mode supported by the implementation

Returns:: The implemented buffer mode.

getInitialExtent

long getInitialExtent()

The initial extent.

getMaximumExtent

long getMaximumExtent()

The maximum extent allowable before a buffer overflow operation will be rejected.

Note: The semantics here differ from those defined by Options.MAXIMUM_EXTENT. The latter specifies the threshold at which a journal will overflow (onto another journal) while this specifies the maximum size to which a buffer is allowed to grow.

Note: This is normally zero (0L), which basically means that the maximum extent is ignored by the IBufferStrategy but respected by the AbstractJournal, resulting in a soft limit on journal overflow.

Returns:: The maximum extent permitted for the buffer -or- 0L iff no limit is imposed.

getExtent

long getExtent()

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.

getUserExtent

long getUserExtent()

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 getExtent() since the latter also reports the space allocated to the journal header and root blocks.

getHeaderSize

int getHeaderSize()

The size of the journal header, including MAGIC, version, and both root blocks. This is used as an offset when computing the address of a record in an underlying file and is ignored by buffer modes that are not backed by a file (e.g., transient) or that are memory mapped (since the map is setup to skip over the header)

truncate

void truncate(long extent)

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.

Parameters:: extent - The new extent of the journal. This value represent the total extent of the journal, including any root blocks together with the user extent.
Throws:: IllegalArgumentException - The user extent MAY NOT be increased beyond the maximum offset for which the journal was provisioned by Options.OFFSET_BITS.

writeRootBlock

void writeRootBlock(IRootBlockView rootBlock,
                    ForceEnum forceOnCommitEnum)

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

Parameters:: rootBlock - The root block. Which root block is indicated by IRootBlockView.isRootBlock0().; forceOnCommit - Governs whether or not the journal is forced to stable storage and whether or not the file metadata for the journal is forced to stable storage. See Options.FORCE_ON_COMMIT.

readRootBlock

ByteBuffer readRootBlock(boolean rootBlock0)

Read the specified root block from the backing file.

transferTo

long transferTo(RandomAccessFile out)
                throws IOException

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.