com.lmax.disruptor

Class SingleProducerSequencer

java.lang.Object

com.lmax.disruptor.AbstractSequencer

com.lmax.disruptor.SingleProducerSequencer

All Implemented Interfaces:

Cursored, Sequenced, Sequencer

public final class SingleProducerSequencer
extends AbstractSequencer

Coordinator for claiming sequences for access to a data structure while tracking dependent Sequences. Not safe for use from multiple threads as it does not implement any barriers.

* Note on Cursored.getCursor(): With this sequencer the cursor value is updated after the call to Sequenced.publish(long) is made.

Field Summary

Fields inherited from interface com.lmax.disruptor.Sequencer

INITIAL_CURSOR_VALUE

Constructor Summary

Constructors

Constructor and Description
SingleProducerSequencer(int bufferSize, WaitStrategy waitStrategy) Construct a Sequencer with the selected wait strategy and buffer size.

Method Summary

Modifier and Type	Method and Description
void	claim(long sequence) Claim a specific sequence.
long	getHighestPublishedSequence(long lowerBound, long availableSequence) Get the highest sequence number that can be safely read from the ring buffer.
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.
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.
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 class com.lmax.disruptor.AbstractSequencer

addGatingSequences, getBufferSize, getCursor, getMinimumSequence, newBarrier, newPoller, removeGatingSequence, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SingleProducerSequencer

public SingleProducerSequencer(int bufferSize,
                               WaitStrategy waitStrategy)

Construct a Sequencer with the selected wait strategy and buffer size.

Parameters:

bufferSize - the size of the buffer that this will sequence over.

waitStrategy - for those waiting on sequences.

Method Detail

hasAvailableCapacity

public boolean hasAvailableCapacity(int requiredCapacity)

Description copied from interface: Sequenced

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.

See Also:

Sequenced.hasAvailableCapacity(int)

next

public long next()

Description copied from interface: Sequenced

Claim the next event in sequence for publishing.

Returns:

the claimed sequence value

See Also:

Sequenced.next()

next

public long next(int n)

Description copied from interface: Sequenced

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

See Also:

Sequenced.next(int)

tryNext

public long tryNext()
             throws InsufficientCapacityException

Description copied from interface: Sequenced

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 - thrown if there is no space available in the ring buffer.

See Also:

Sequenced.tryNext()

tryNext

public long tryNext(int n)
             throws InsufficientCapacityException

Description copied from interface: Sequenced

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 Sequenced.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 - thrown if there is no space available in the ring buffer.

See Also:

Sequenced.tryNext(int)

remainingCapacity

public long remainingCapacity()

Description copied from interface: Sequenced

Get the remaining capacity for this sequencer.

Returns:

The number of slots remaining.

See Also:

Sequenced.remainingCapacity()

claim

public void claim(long sequence)

Description copied from interface: Sequencer

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

Parameters:

sequence - The sequence to initialise too.

See Also:

Sequencer.claim(long)

publish

public void publish(long sequence)

Description copied from interface: Sequenced

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

Parameters:

sequence - the sequence to be published.

See Also:

Sequenced.publish(long)

publish

public void publish(long lo,
                    long hi)

Description copied from interface: Sequenced

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

See Also:

Sequenced.publish(long, long)

isAvailable

public boolean isAvailable(long sequence)

Description copied from interface: Sequencer

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

See Also:

Sequencer.isAvailable(long)

getHighestPublishedSequence

public long getHighestPublishedSequence(long lowerBound,
                                        long availableSequence)

Description copied from interface: Sequencer

Get the highest sequence number that can be safely read from the ring buffer. Depending on the implementation of the Sequencer this call may need to scan a number of values in the Sequencer. The scan will range from nextSequence to availableSequence. If there are no available values >= nextSequence the return value will be nextSequence - 1. To work correctly a consumer should pass a value that is 1 higher than the last sequence that was successfully processed.

Parameters:

lowerBound - The sequence to start scanning from.

availableSequence - The sequence to scan to.

Returns:

The highest value that can be safely read, will be at least nextSequence - 1.