org.apache.ignite.internal.processors.cache.persistence.wal

Class SegmentedRingByteBuffer

java.lang.Object

org.apache.ignite.internal.processors.cache.persistence.wal.SegmentedRingByteBuffer

public class SegmentedRingByteBuffer
extends Object

Segmented ring byte buffer that represents multi producer/single consumer queue that can be used by multiple writer threads and one reader thread.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SegmentedRingByteBuffer.BufferMode Buffer mode.
class	SegmentedRingByteBuffer.ReadSegment Segment available for data reading.
class	SegmentedRingByteBuffer.WriteSegment Segment available for data writing.

Field Summary

Fields

Modifier and Type	Field and Description
ByteBuffer	buf Buffer.

Constructor Summary

Constructors

Constructor and Description
SegmentedRingByteBuffer(int cap, long maxSegmentSize, SegmentedRingByteBuffer.BufferMode mode) Creates ring buffer with given capacity.
SegmentedRingByteBuffer(int cap, long maxSegmentSize, SegmentedRingByteBuffer.BufferMode mode, DataStorageMetricsImpl metrics) Creates ring buffer with given capacity.
SegmentedRingByteBuffer(MappedByteBuffer buf, DataStorageMetricsImpl metrics) Creates ring buffer with given capacity which mapped to file.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the buffer.
void	free() Frees allocated memory in case of direct byte buffer.
void	init(long pos) Performs initialization of ring buffer state.
SegmentedRingByteBuffer.BufferMode	mode() Returns buffer mode.
SegmentedRingByteBuffer.WriteSegment	offer(int size) Reserves size bytes in SegmentedRingByteBuffer and returns instance of SegmentedRingByteBuffer.WriteSegment class that points to wrapped ByteBuffer instance with corresponding capacity.
SegmentedRingByteBuffer.WriteSegment	offerSafe(int size) Behaves like offer(int) but in safe manner: there are no any concurrent threads and buffer in closed state.
List<SegmentedRingByteBuffer.ReadSegment>	poll() Retrieves list of SegmentedRingByteBuffer.ReadSegment instances that point to ByteBuffer that contains all data available for reading from SegmentedRingByteBuffer or null if there are no available data for reading.
List<SegmentedRingByteBuffer.ReadSegment>	poll(long pos) Retrieves list of SegmentedRingByteBuffer.ReadSegment instances that point to ByteBuffer that contains data available for reading from SegmentedRingByteBuffer limited by pos parameter or null if there are no available data for reading.
SegmentedRingByteBuffer	reset() Resets the state of the buffer and returns new instance but with the same underlying buffer.
long	tail() Returns actual buffer tail.

Methods inherited from class java.lang.Object

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

Field Detail

buf

public final ByteBuffer buf

Buffer.

Constructor Detail

SegmentedRingByteBuffer

public SegmentedRingByteBuffer(int cap,
                               long maxSegmentSize,
                               SegmentedRingByteBuffer.BufferMode mode)

Creates ring buffer with given capacity.

Parameters:

cap - Buffer's capacity.

maxSegmentSize - Max segment size.

mode - Buffer mode.

SegmentedRingByteBuffer

public SegmentedRingByteBuffer(int cap,
                               long maxSegmentSize,
                               SegmentedRingByteBuffer.BufferMode mode,
                               DataStorageMetricsImpl metrics)

Creates ring buffer with given capacity.

Parameters:

cap - Buffer's capacity.

maxSegmentSize - Max segment size.

mode - Buffer mode.

metrics - Metrics.

SegmentedRingByteBuffer

public SegmentedRingByteBuffer(MappedByteBuffer buf,
                               DataStorageMetricsImpl metrics)

Creates ring buffer with given capacity which mapped to file.

Parameters:

buf - MappedByteBuffer instance.

metrics - Metrics.

Method Detail

init

public void init(long pos)

Performs initialization of ring buffer state.

Parameters:

pos - Position.

mode

public SegmentedRingByteBuffer.BufferMode mode()

Returns buffer mode.

Returns:

Buffer mode.

tail

public long tail()

Returns actual buffer tail.

Returns:

Buffer tail.

offer

public SegmentedRingByteBuffer.WriteSegment offer(int size)

Reserves size bytes in SegmentedRingByteBuffer and returns instance of SegmentedRingByteBuffer.WriteSegment class that points to wrapped ByteBuffer instance with corresponding capacity. This ByteBuffer instance should be used only for data writing to SegmentedRingByteBuffer.

Returned result can be null in case of requested amount of bytes greater then available space in SegmentedRingByteBuffer. Also SegmentedRingByteBuffer.WriteSegment.buffer() can return null in case of maxSegmentSize value is exceeded. In this case buffer will be closed in order to prevent any concurrent threads from trying of reserve new segment.

This method can be invoked by many producer threads and each producer will get own ByteBuffer instance that mapped to own SegmentedRingByteBuffer slice.

Once the data has been written into the ByteBuffer client code must notify SegmentedRingByteBuffer instance using SegmentedRingByteBuffer.WriteSegment.release() method in order to provide possibility to consumer get data for reading.

Parameters:

size - Amount of bytes for reserve.

Returns:

SegmentedRingByteBuffer.WriteSegment instance that point to ByteBuffer instance with given size. null if buffer space is not enough.

offerSafe

public SegmentedRingByteBuffer.WriteSegment offerSafe(int size)

Behaves like offer(int) but in safe manner: there are no any concurrent threads and buffer in closed state.

Parameters:

size - Amount of bytes for reserve.

Returns:

SegmentedRingByteBuffer.WriteSegment instance that point to ByteBuffer instance with given size. null if buffer space is not enough.

close

public void close()

Closes the buffer.

poll

public List<SegmentedRingByteBuffer.ReadSegment> poll()

Retrieves list of SegmentedRingByteBuffer.ReadSegment instances that point to ByteBuffer that contains all data available for reading from SegmentedRingByteBuffer or null if there are no available data for reading.

This method can be invoked only by one consumer thread.

Once the data has been read from the returned SegmentedRingByteBuffer.ReadSegment client code must notify SegmentedRingByteBuffer instance using SegmentedRingByteBuffer.ReadSegment.release() method in order to release occupied space in the SegmentedRingByteBuffer and make it available for writing.

Returns:

List of ReadSegment instances with all available data for reading or null if there are no available data.

poll

public List<SegmentedRingByteBuffer.ReadSegment> poll(long pos)

Retrieves list of SegmentedRingByteBuffer.ReadSegment instances that point to ByteBuffer that contains data available for reading from SegmentedRingByteBuffer limited by pos parameter or null if there are no available data for reading.

This method can be invoked only by one consumer thread.

Once the data has been read from the returned SegmentedRingByteBuffer.ReadSegment client code must notify SegmentedRingByteBuffer instance using SegmentedRingByteBuffer.ReadSegment.release() method in order to release occupied space in the SegmentedRingByteBuffer and make it available for writing.

Parameters:

pos - End position in buffer.

Returns:

List of ReadSegment instances with all available data for reading or null if there are no available data.

free

public void free()

Frees allocated memory in case of direct byte buffer.

reset

public SegmentedRingByteBuffer reset()

Resets the state of the buffer and returns new instance but with the same underlying buffer.