com.hazelcast.client.impl.protocol.template

Interface RingbufferCodecTemplate

public interface RingbufferCodecTemplate

Method Summary

Methods

Modifier and Type	Method and Description
Object	add(String name, int overflowPolicy, Data value) Adds an item to the tail of the Ringbuffer.
Object	addAll(String name, List<Data> valueList, int overflowPolicy) Adds all the items of a collection to the tail of the Ringbuffer.
Object	capacity(String name) Returns the capacity of this Ringbuffer.
Object	headSequence(String name) Returns the sequence of the head.
Object	readMany(String name, long startSequence, int minCount, int maxCount, Data filter) Reads a batch of items from the Ringbuffer.
Object	readOne(String name, long sequence) Reads one item from the Ringbuffer.
Object	remainingCapacity(String name) Returns the remaining capacity of the ringbuffer.
Object	size(String name) Returns number of items in the ringbuffer.
Object	tailSequence(String name) Returns the sequence of the tail.

Method Detail

size

Object size(String name)

Returns number of items in the ringbuffer. If no ttl is set, the size will always be equal to capacity after the head completed the first looparound the ring. This is because no items are getting retired.

Parameters:

name - Name of the Ringbuffer

Returns:

the size

tailSequence

Object tailSequence(String name)

Returns the sequence of the tail. The tail is the side of the ringbuffer where the items are added to. The initial value of the tail is -1.

Parameters:

name - Name of the Ringbuffer

Returns:

the sequence of the tail

headSequence

Object headSequence(String name)

Returns the sequence of the head. The head is the side of the ringbuffer where the oldest items in the ringbuffer are found. If the RingBuffer is empty, the head will be one more than the tail. The initial value of the head is 0 (1 more than tail).

Parameters:

name - Name of the Ringbuffer

Returns:

the sequence of the head

capacity

Object capacity(String name)

Returns the capacity of this Ringbuffer.

Parameters:

name - Name of the Ringbuffer

Returns:

the capacity

remainingCapacity

Object remainingCapacity(String name)

Returns the remaining capacity of the ringbuffer. The returned value could be stale as soon as it is returned. If ttl is not set, the remaining capacity will always be the capacity.

Parameters:

name - Name of the Ringbuffer

Returns:

the remaining capacity

add

Object add(String name,
         int overflowPolicy,
         Data value)

Adds an item to the tail of the Ringbuffer. If there is space in the ringbuffer, the call will return the sequence of the written item. If there is no space, it depends on the overflow policy what happens: OverflowPolicy OVERWRITE we just overwrite the oldest item in the ringbuffer and we violate the ttl OverflowPolicy FAIL we return -1. The reason that FAIL exist is to give the opportunity to obey the ttl.

This sequence will always be unique for this Ringbuffer instance so it can be used as a unique id generator if you are publishing items on this Ringbuffer. However you need to take care of correctly determining an initial id when any node uses the ringbuffer for the first time. The most reliable way to do that is to write a dummy item into the ringbuffer and use the returned sequence as initial id. On the reading side, this dummy item should be discard. Please keep in mind that this id is not the sequence of the item you are about to publish but from a previously published item. So it can't be used to find that item.

Parameters:

name - Name of the Ringbuffer

overflowPolicy - the OverflowPolicy to use.

value - to item to add

Returns:

the sequence of the added item, or -1 if the add failed.

readOne

Object readOne(String name,
             long sequence)

Reads one item from the Ringbuffer. If the sequence is one beyond the current tail, this call blocks until an item is added. This method is not destructive unlike e.g. a queue.take. So the same item can be read by multiple readers or it can be read multiple times by the same reader. Currently it isn't possible to control how long this call is going to block. In the future we could add e.g. tryReadOne(long sequence, long timeout, TimeUnit unit).

Parameters:

name - Name of the Ringbuffer

sequence - the sequence of the item to read.

Returns:

the read item

addAll

Object addAll(String name,
            List<Data> valueList,
            int overflowPolicy)

Adds all the items of a collection to the tail of the Ringbuffer. A addAll is likely to outperform multiple calls to add(Object) due to better io utilization and a reduced number of executed operations. If the batch is empty, the call is ignored. When the collection is not empty, the content is copied into a different data-structure. This means that: after this call completes, the collection can be re-used. the collection doesn't need to be serializable. If the collection is larger than the capacity of the ringbuffer, then the items that were written first will be overwritten. Therefor this call will not block. The items are inserted in the order of the Iterator of the collection. If an addAll is executed concurrently with an add or addAll, no guarantee is given that items are contiguous. The result of the future contains the sequenceId of the last written item

Parameters:

name - Name of the Ringbuffer

valueList - the batch of items to add

overflowPolicy - the overflowPolicy to use

Returns:

the ICompletableFuture to synchronize on completion.

readMany

Object readMany(String name,
              long startSequence,
              int minCount,
              int maxCount,
              @Nullable
              Data filter)

Reads a batch of items from the Ringbuffer. If the number of available items after the first read item is smaller than the maxCount, these items are returned. So it could be the number of items read is smaller than the maxCount. If there are less items available than minCount, then this call blacks. Reading a batch of items is likely to perform better because less overhead is involved. A filter can be provided to only select items that need to be read. If the filter is null, all items are read. If the filter is not null, only items where the filter function returns true are returned. Using filters is a good way to prevent getting items that are of no value to the receiver. This reduces the amount of IO and the number of operations being executed, and can result in a significant performance improvement.

Parameters:

name - Name of the Ringbuffer

startSequence - the startSequence of the first item to read

minCount - the minimum number of items to read.

maxCount - the maximum number of items to read.

filter - Filter is allowed to be null, indicating there is no filter.

Returns:

a future containing the items read.