org.apache.hadoop.hbase.io.hfile.bucket

Interface IOEngine

All Known Implementing Classes:

ByteBufferIOEngine, ExclusiveMemoryMmapIOEngine, FileIOEngine, FileMmapIOEngine, PersistentIOEngine, SharedMemoryMmapIOEngine

@InterfaceAudience.Private
public interface IOEngine

A class implementing IOEngine interface supports data services for BucketCache.

Method Summary

Modifier and Type	Method and Description
boolean	isPersistent()
Cacheable	read(BucketEntry be) Transfers data from IOEngine to a Cacheable object.
void	shutdown() Shutdown the IOEngine
void	sync() Sync the data to IOEngine after writing
default boolean	usesSharedMemory() IOEngine uses shared memory means, when reading Cacheable from it, those refers to the same memory area as used by the Engine for caching it.
void	write(ByteBuffer srcBuffer, long offset) Transfers data from the given byte buffer to IOEngine
void	write(ByteBuff srcBuffer, long offset) Transfers the data from the given MultiByteBuffer to IOEngine

Method Detail

isPersistent

boolean isPersistent()

Returns:

true if persistent storage is supported for the cache when shutdown

usesSharedMemory

default boolean usesSharedMemory()

IOEngine uses shared memory means, when reading Cacheable from it, those refers to the same memory area as used by the Engine for caching it.

Returns:

true when IOEngine using shared memory.

read

Cacheable read(BucketEntry be)
        throws IOException

Transfers data from IOEngine to a Cacheable object.

Parameters:

be - maintains an (offset,len,refCnt) inside.

Returns:

Cacheable which will wrap the NIO ByteBuffers from IOEngine.

Throws:

IOException - when any IO error happen

IllegalArgumentException - when the length of the ByteBuff read is less than 'len'

write

void write(ByteBuffer srcBuffer,
           long offset)
    throws IOException

Transfers data from the given byte buffer to IOEngine

Parameters:

srcBuffer - the given byte buffer from which bytes are to be read

offset - The offset in the IO engine where the first byte to be written

Throws:

IOException

write

void write(ByteBuff srcBuffer,
           long offset)
    throws IOException

Transfers the data from the given MultiByteBuffer to IOEngine

Parameters:

srcBuffer - the given MultiBytebufffers from which bytes are to be read

offset - the offset in the IO engine where the first byte to be written

Throws:

IOException

sync

void sync()
   throws IOException

Sync the data to IOEngine after writing

Throws:

IOException

shutdown

void shutdown()

Shutdown the IOEngine