com.lmax.disruptor
Class Sequencer

java.lang.Object
  com.lmax.disruptor.Sequencer

Direct Known Subclasses:

RingBuffer

public class Sequencer
extends java.lang.Object

Coordinator for claiming sequences for access to a data structure while tracking dependent Sequences

Field Summary

static long

INITIAL_CURSOR_VALUE Set to -1 as sequence starting point

Constructor Summary

Sequencer(ClaimStrategy claimStrategy, WaitStrategy waitStrategy)
Construct a Sequencer with the selected strategies.

Method Summary

long	claim(long sequence) Claim a specific sequence when only one publisher is involved.
void	forcePublish(long sequence) Force the publication of a cursor sequence.
int	getBufferSize() The capacity of the data structure to hold entries.
long	getCursor() Get the value of the cursor indicating the published sequence.
boolean	hasAvailableCapacity(int availableCapacity) Has the buffer got capacity to allocate another sequence.
SequenceBarrier	newBarrier(Sequence... sequencesToTrack) Create a SequenceBarrier that gates on the the cursor and a list of Sequences
BatchDescriptor	newBatchDescriptor(int size) Create a new BatchDescriptor that is the minimum of the requested size and the buffer size.
long	next() Claim the next event in sequence for publishing.
BatchDescriptor	next(BatchDescriptor batchDescriptor) Claim the next batch of sequence numbers for publishing.
void	publish(BatchDescriptor batchDescriptor) Publish the batch of events in sequence.
void	publish(long sequence) Publish an event and make it visible to EventProcessors
long	remainingCapacity()
void	setGatingSequences(Sequence... sequences) Set the sequences that will gate publishers to prevent the buffer wrapping.
long	tryNext(int requiredCapacity) Attempt to claim the next event in sequence for publishing.

Methods inherited from class java.lang.Object

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

Field Detail

INITIAL_CURSOR_VALUE

public static final long INITIAL_CURSOR_VALUE

Set to -1 as sequence starting point

See Also:

Constant Field Values

Constructor Detail

Sequencer

public Sequencer(ClaimStrategy claimStrategy,
                 WaitStrategy waitStrategy)

Construct a Sequencer with the selected strategies.

Parameters:

claimStrategy - for those claiming sequences.

waitStrategy - for those waiting on sequences.

Method Detail

setGatingSequences

public void setGatingSequences(Sequence... sequences)

Set the sequences that will gate publishers to prevent the buffer wrapping. This method must be called prior to claiming sequences otherwise a NullPointerException will be thrown.

Parameters:

sequences - to be to be gated on.

newBarrier

public SequenceBarrier newBarrier(Sequence... sequencesToTrack)

Create a SequenceBarrier that gates on the the cursor and a list of Sequences

Parameters:

sequencesToTrack - this barrier will track

Returns:

the barrier gated as required

newBatchDescriptor

public BatchDescriptor newBatchDescriptor(int size)

Create a new BatchDescriptor that is the minimum of the requested size and the buffer size.

Parameters:

size - for the batch

Returns:

the new BatchDescriptor

getBufferSize

public int getBufferSize()

The capacity of the data structure to hold entries.

Returns:

the size of the RingBuffer.

getCursor

public long getCursor()

Get the value of the cursor indicating the published sequence.

Returns:

value of the cursor for events that have been published.

hasAvailableCapacity

public boolean hasAvailableCapacity(int availableCapacity)

Has the buffer got capacity to allocate another sequence. This is a concurrent method so the response should only be taken as an indication of available capacity.

Parameters:

availableCapacity - in the buffer

Returns:

true if the buffer has the capacity to allocate the next sequence otherwise false.

next

public long next()

Claim the next event in sequence for publishing.

Returns:

the claimed sequence value

tryNext

public long tryNext(int requiredCapacity)
             throws InsufficientCapacityException

Attempt to claim the next event in sequence for publishing. Will return the number of the slot if there is at least requiredCapacity slots available.

Parameters:

requiredCapacity - as slots in the data structure

Returns:

the claimed sequence value

Throws:

InsufficientCapacityException - when the requiredCapacity is not available

next

public BatchDescriptor next(BatchDescriptor batchDescriptor)

Claim the next batch of sequence numbers for publishing.

Parameters:

batchDescriptor - to be updated for the batch range.

Returns:

the updated batchDescriptor.

claim

public long claim(long sequence)

Claim a specific sequence when only one publisher is involved.

Parameters:

sequence - to be claimed.

Returns:

sequence just claimed.

publish

public void publish(long sequence)

Publish an event and make it visible to EventProcessors

Parameters:

sequence - to be published

publish

public void publish(BatchDescriptor batchDescriptor)

Publish the batch of events in sequence.

Parameters:

batchDescriptor - to be published.

forcePublish

public void forcePublish(long sequence)

Force the publication of a cursor sequence. Only use this method when forcing a sequence and you are sure only one publisher exists. This will cause the cursor to advance to this sequence.

Parameters:

sequence - which is to be forced for publication.

remainingCapacity

public long remainingCapacity()