com.bigdata.io.writecache

Class WriteCache.FileChannelWriteCache

java.lang.Object

com.bigdata.io.writecache.WriteCache

com.bigdata.io.writecache.WriteCache.FileChannelWriteCache

All Implemented Interfaces:

IWriteCache

Enclosing class:

WriteCache

public static class WriteCache.FileChannelWriteCache
extends WriteCache

A WriteCache implementation suitable for an append-only file such as the WORMStrategy or the output file of the IndexSegmentBuilder.

Author:

Bryan Thompson

Nested Class Summary

Nested classes/interfaces inherited from class com.bigdata.io.writecache.WriteCache

WriteCache.FileChannelScatteredWriteCache, WriteCache.FileChannelWriteCache, WriteCache.HAPackage, WriteCache.ReadCache, WriteCache.RecordMetadata

Field Summary

Fields

Modifier and Type	Field and Description
protected long	baseOffset An offset which will be applied to each record written onto the backing FileChannel.
IReopenChannel<FileChannel>	opener Used to re-open the FileChannel in this class.

Fields inherited from class com.bigdata.io.writecache.WriteCache

counters, log, recordMap

Constructor Summary

Constructors

Constructor and Description
WriteCache.FileChannelWriteCache(long baseOffset, IBufferAccess buf, boolean useChecksum, boolean isHighlyAvailable, boolean bufferHasData, IReopenChannel<FileChannel> opener, long fileExtent)

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	writeOnChannel(ByteBuffer data, long firstOffset, Map<Long,WriteCache.RecordMetadata> recordMap, long nanos) Write the data from the buffer onto the channel.

Methods inherited from class com.bigdata.io.writecache.WriteCache

allocate, bytesWritten, capacity, close, closeForWrites, contains, decrementReferenceCount, flush, flush, getCompressorKey, getCounters, getFileExtent, getLastOffset, getReferenceCount, incrementReferenceCount, isClosedForWrites, read, registerWriteStatus, reset, resetRecordMapFromBuffer, resetRecordMapFromBuffer, setFileExtent, setFirstOffset, setRecordMap, toString, write

Methods inherited from class java.lang.Object

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

Field Detail

baseOffset

protected final long baseOffset

An offset which will be applied to each record written onto the backing FileChannel. The offset is generally the size of the root blocks for a journal or the checkpoint record for an index segment. It can be zero if you do not have anything at the head of the file.

Note: This implies that writing the root blocks is done separately in the protocol since you can't write below this offset otherwise.

opener

public final IReopenChannel<FileChannel> opener

Used to re-open the FileChannel in this class.

Constructor Detail

WriteCache.FileChannelWriteCache

public WriteCache.FileChannelWriteCache(long baseOffset,
                                IBufferAccess buf,
                                boolean useChecksum,
                                boolean isHighlyAvailable,
                                boolean bufferHasData,
                                IReopenChannel<FileChannel> opener,
                                long fileExtent)
                                 throws InterruptedException

Parameters:

baseOffset - An offset

buf -

opener -

Throws:

InterruptedException

Method Detail

writeOnChannel

protected boolean writeOnChannel(ByteBuffer data,
                     long firstOffset,
                     Map<Long,WriteCache.RecordMetadata> recordMap,
                     long nanos)
                          throws InterruptedException,
                                 IOException

Description copied from class: WriteCache

Write the data from the buffer onto the channel. This method provides a uniform means to request that the buffer write itself onto the backing channel, regardless of whether the channel is backed by a file, a socket, etc.

Implementations of this method MAY support gathered writes, depending on the channel. The necessary information to perform a gathered write is present in the recordMap. On the other hand, the implementation MAY require that the records in the cache are laid out for a WORM, in which case WriteCache.getFirstOffset() provides the starting offset for the data to be written. The application MUST coordinate the requirements for a R/W or WORM store with the use of the WriteCache and the means to write on the backing channel.

Specified by:

writeOnChannel in class WriteCache

Parameters:

data - The data to be written. Only the dirty bytes are visible in this view. The implementation should write all bytes from the current position to the limit.

firstOffset - The offset of the first record in the recordMap into the file (may be relative to a base offset within the file). This is provided as an optimization for the WORM which writes its records contiguously on the backing store.

recordMap - The mapping of record offsets onto metadata about those records.

nanos - The timeout for the operation in nanoseconds.

Returns:

true if the operation was completed successfully within the time alloted.

Throws:

InterruptedException - if the thread was interrupted.

IOException - if there was an IO problem.