com.lmax.disruptor

Interface Sequencer

All Superinterfaces:

Cursored

All Known Implementing Classes:

AbstractSequencer, MultiProducerSequencer, SingleProducerSequencer

public interface Sequencer
extends Cursored

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

Field Summary

Fields

Modifier and Type	Field and Description
static long	INITIAL_CURSOR_VALUE Set to -1 as sequence starting point

Method Summary

Methods

Modifier and Type	Method and Description
void	addGatingSequences(Sequence... gatingSequences) Add the specified gating sequences to this instance of the Disruptor.
void	claim(long sequence) Claim a specific sequence.
void	ensureAvailable(long sequence) Ensure a given sequence has been published and the event is now available. Blocks if the sequence is not available yet.
int	getBufferSize() The capacity of the data structure to hold entries.
long	getMinimumSequence() Get the minimum sequence value from all of the gating sequences added to this ringBuffer.
boolean	hasAvailableCapacity(int requiredCapacity) Has the buffer got capacity to allocate another sequence.
boolean	isAvailable(long sequence) Confirms if a sequence is published and the event is available for use; non-blocking.
SequenceBarrier	newBarrier(Sequence... sequencesToTrack) Create a new SequenceBarrier to be used by an EventProcessor to track which messages are available to be read from the ring buffer given a list of sequences to track.
long	next() Claim the next event in sequence for publishing.
long	next(int n) Claim the next n events in sequence for publishing.
void	publish(long sequence) Publishes a sequence.
void	publish(long lo, long hi) Batch publish sequences.
long	remainingCapacity() Get the remaining capacity for this sequencer.
boolean	removeGatingSequence(Sequence sequence) Remove the specified sequence from this sequencer.
long	tryNext() Attempt to claim the next event in sequence for publishing.
long	tryNext(int n) Attempt to claim the next n events in sequence for publishing.

Methods inherited from interface com.lmax.disruptor.Cursored

getCursor

Field Detail

INITIAL_CURSOR_VALUE

static final long INITIAL_CURSOR_VALUE

Set to -1 as sequence starting point

See Also:

Constant Field Values

Method Detail

getBufferSize

int getBufferSize()

The capacity of the data structure to hold entries.

Returns:

the size of the RingBuffer.

hasAvailableCapacity

boolean hasAvailableCapacity(int requiredCapacity)

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:

requiredCapacity - in the buffer

Returns:

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

next

long next()

Claim the next event in sequence for publishing.

Returns:

the claimed sequence value

next

long next(int n)

Claim the next n events in sequence for publishing. This is for batch event producing. Using batch producing requires a little care and some math.

 int n = 10;
 long hi = sequencer.next(n);
 long lo = hi - (n - 1);
 for (long sequence = lo; sequence <= hi; sequence++) {
     // Do work.
 }
 sequencer.publish(lo, hi);
 

Parameters:

n - the number of sequences to claim

Returns:

the highest claimed sequence value

tryNext

long tryNext()
             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.

Returns:

the claimed sequence value

Throws:

InsufficientCapacityException

tryNext

long tryNext(int n)
             throws InsufficientCapacityException

Attempt to claim the next n events in sequence for publishing. Will return the highest numbered slot if there is at least requiredCapacity slots available. Have a look at next() for a description on how to use this method.

Parameters:

n - the number of sequences to claim

Returns:

the claimed sequence value

Throws:

InsufficientCapacityException

remainingCapacity

long remainingCapacity()

Get the remaining capacity for this sequencer.

Returns:

The number of slots remaining.

claim

void claim(long sequence)

Claim a specific sequence. Only used if initialising the ring buffer to a specific value.

Parameters:

sequence - The sequence to initialise too.

publish

void publish(long sequence)

Publishes a sequence. Call when the event has been filled.

Parameters:

sequence -

publish

void publish(long lo,
           long hi)

Batch publish sequences. Called when all of the events have been filled.

Parameters:

lo - first sequence number to publish

hi - last sequence number to publish

isAvailable

boolean isAvailable(long sequence)

Confirms if a sequence is published and the event is available for use; non-blocking.

Parameters:

sequence - of the buffer to check

Returns:

true if the sequence is available for use, false if not

ensureAvailable

void ensureAvailable(long sequence)

Ensure a given sequence has been published and the event is now available.

Blocks if the sequence is not available yet.

Parameters:

sequence - of the event to wait for

addGatingSequences

void addGatingSequences(Sequence... gatingSequences)

Add the specified gating sequences to this instance of the Disruptor. They will safely and atomically added to the list of gating sequences.

Parameters:

gatingSequences - The sequences to add.

removeGatingSequence

boolean removeGatingSequence(Sequence sequence)

Remove the specified sequence from this sequencer.

Parameters:

sequence - to be removed.

Returns:

true if this sequence was found, false otherwise.

newBarrier

SequenceBarrier newBarrier(Sequence... sequencesToTrack)

Create a new SequenceBarrier to be used by an EventProcessor to track which messages are available to be read from the ring buffer given a list of sequences to track.

Parameters:

sequencesToTrack -

Returns:

A sequence barrier that will track the specified sequences.

See Also:

SequenceBarrier

getMinimumSequence

long getMinimumSequence()

Get the minimum sequence value from all of the gating sequences added to this ringBuffer.

Returns:

The minimum gating sequence or the cursor sequence if no sequences have been added.