org.agrona.concurrent.ringbuffer

Class OneToOneRingBuffer

java.lang.Object

org.agrona.concurrent.ringbuffer.OneToOneRingBuffer

All Implemented Interfaces:

RingBuffer

public class OneToOneRingBuffer
extends java.lang.Object
implements RingBuffer

A ring-buffer that supports the exchange of messages from a single producer to a single consumer.

This single producer ring-buffer can be used in combination a consumer using the ManyToOneRingBuffer provided no other producers are accessing the same ring-buffer.

Field Summary

Fields

Modifier and Type	Field and Description
static int	PADDING_MSG_TYPE_ID Record type is padding to prevent fragmentation in the buffer.

Constructor Summary

Constructors

Constructor and Description
OneToOneRingBuffer(AtomicBuffer buffer) Construct a new RingBuffer based on an underlying AtomicBuffer.

Method Summary

Modifier and Type	Method and Description
AtomicBuffer	buffer() Get the underlying buffer used by the RingBuffer for storage.
int	capacity() Get the capacity of the ring-buffer in bytes for exchange.
long	consumerHeartbeatTime() The time of the last consumer heartbeat.
void	consumerHeartbeatTime(long time) Set the time of the last consumer heartbeat.
long	consumerPosition() The position in bytes from start up for the consumers.
int	maxMsgLength() The maximum message length in bytes supported by the underlying ring buffer.
long	nextCorrelationId() Get the next value that can be used for a correlation id on an message when a response needs to be correlated.
long	producerPosition() The position in bytes from start up of the producers.
int	read(MessageHandler handler) Read as many messages as are available to the end of the ring buffer.
int	read(MessageHandler handler, int messageCountLimit) Read as many messages as are available to end of the ring buffer to up a supplied maximum.
int	size() Size of the buffer backlog in bytes between producers and consumers.
boolean	unblock() Unblock a multi-producer ring buffer when a producer has died during the act of offering.
boolean	write(int msgTypeId, DirectBuffer srcBuffer, int srcIndex, int length) Non-blocking write of an message to an underlying ring-buffer.

Methods inherited from class java.lang.Object

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

Field Detail

PADDING_MSG_TYPE_ID

public static final int PADDING_MSG_TYPE_ID

Record type is padding to prevent fragmentation in the buffer.

See Also:

Constant Field Values

Constructor Detail

OneToOneRingBuffer

public OneToOneRingBuffer(AtomicBuffer buffer)

Construct a new RingBuffer based on an underlying AtomicBuffer. The underlying buffer must a power of 2 in size plus sufficient space for the RingBufferDescriptor.TRAILER_LENGTH.

Parameters:

buffer - via which events will be exchanged.

Throws:

java.lang.IllegalStateException - if the buffer capacity is not a power of 2 plus RingBufferDescriptor.TRAILER_LENGTH in capacity.

Method Detail

capacity

public int capacity()

Get the capacity of the ring-buffer in bytes for exchange.

Specified by:

capacity in interface RingBuffer

Returns:

the capacity of the ring-buffer in bytes for exchange.

write

public boolean write(int msgTypeId,
                     DirectBuffer srcBuffer,
                     int srcIndex,
                     int length)

Non-blocking write of an message to an underlying ring-buffer.

Specified by:

write in interface RingBuffer

Parameters:

msgTypeId - type of the message encoding.

srcBuffer - containing the encoded binary message.

srcIndex - at which the encoded message begins.

length - of the encoded message in bytes.

Returns:

true if written to the ring-buffer, or false if insufficient space exists.

read

public int read(MessageHandler handler)

Read as many messages as are available to the end of the ring buffer.

If the ring buffer wraps or encounters a type of record, such a a padding record, then an implementation may choose to return and expect the caller to try again. The RingBuffer.size() method may be called to determine of a backlog of message bytes remains in the ring buffer.

Specified by:

read in interface RingBuffer

Parameters:

handler - to be called for processing each message in turn.

Returns:

the number of messages that have been processed.

read

public int read(MessageHandler handler,
                int messageCountLimit)

Read as many messages as are available to end of the ring buffer to up a supplied maximum.

If the ring buffer wraps or encounters a type of record, such a a padding record, then an implementation may choose to return and expect the caller to try again. The RingBuffer.size() method may be called to determine of a backlog of message bytes remains in the ring buffer.

Specified by:

read in interface RingBuffer

Parameters:

handler - to be called for processing each message in turn.

messageCountLimit - the number of messages will be read in a single invocation.

Returns:

the number of messages that have been processed.

maxMsgLength

public int maxMsgLength()

The maximum message length in bytes supported by the underlying ring buffer.

Specified by:

maxMsgLength in interface RingBuffer

Returns:

the maximum message length in bytes supported by the underlying ring buffer.

nextCorrelationId

public long nextCorrelationId()

Get the next value that can be used for a correlation id on an message when a response needs to be correlated.

This method should be thread safe.

Specified by:

nextCorrelationId in interface RingBuffer

Returns:

the next value in the correlation sequence.

buffer

public AtomicBuffer buffer()

Get the underlying buffer used by the RingBuffer for storage.

Specified by:

buffer in interface RingBuffer

Returns:

the underlying buffer used by the RingBuffer for storage.

consumerHeartbeatTime

public void consumerHeartbeatTime(long time)

Set the time of the last consumer heartbeat.

Note: The value for time must be valid across processes which means System.nanoTime() is not a valid option.

Specified by:

consumerHeartbeatTime in interface RingBuffer

Parameters:

time - of the last consumer heartbeat.

consumerHeartbeatTime

public long consumerHeartbeatTime()

The time of the last consumer heartbeat.

Specified by:

consumerHeartbeatTime in interface RingBuffer

Returns:

the time of the last consumer heartbeat.

producerPosition

public long producerPosition()

The position in bytes from start up of the producers. The figure includes the headers. This is the range they are working with but could still be in the act of working with.

Specified by:

producerPosition in interface RingBuffer

Returns:

number of bytes produced by the producers in claimed space.

consumerPosition

public long consumerPosition()

The position in bytes from start up for the consumers. The figure includes the headers.

Specified by:

consumerPosition in interface RingBuffer

Returns:

the count of bytes consumed by the consumers.

size

public int size()

Size of the buffer backlog in bytes between producers and consumers. The value includes the size of headers.

This method gives a concurrent snapshot of the buffer whereby a concurrent read or write may be partially complete and thus the value should be taken as an indication.

Specified by:

size in interface RingBuffer

Returns:

size of the backlog of bytes in the buffer between producers and consumers.

unblock

public boolean unblock()

Unblock a multi-producer ring buffer when a producer has died during the act of offering. The operation will scan from the consumer position up to the producer position.

If no action is required at the position then none will be taken.

Specified by:

unblock in interface RingBuffer

Returns:

true of an unblocking action was taken otherwise false.