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Interface Ringbuffer<E>

A Ringbuffer is a data structure where the content is stored in a ring-like structure. A ringbuffer has a fixed capacity, so it won't grow beyond that capacity and endanger the stability of the system. If that capacity is exceeded, the oldest item in the ringbuffer is overwritten.

Methods that require serialization/deserialization may throw RangeError, e.g when there is no suitable serializer for a certain type.

Type parameters

  • E

Hierarchy

Index

Methods

Methods

add

  • Adds an item to the tail of this Ringbuffer. Overflow policy determines what will happen if there is no space left in this ringbuffer. If OVERWRITE was passed, the new item will overwrite the oldest one regardless of the configured time-to-live.

    In the case when FAIL was specified the add operation will keep failing until the oldest item in this Ringbuffer will reach its time-to-live.

    The returned value is the sequence number of the added item. You can read the added item using this number.

    Parameters

    • item: E

      the item to add

    • Optional overflowPolicy: OverflowPolicy

      overflow policy to be used

    Returns Promise<Long>

    the sequence of the added item or -1 if the insert did not succeed

addAll

  • Adds all items in the specified array to the tail of this Ringbuffer. The behavior of this method is essentially the same as the one of the add method.

    The method does not guarantee that the inserted items will have contiguous sequence numbers.

    Parameters

    • items: E[]

      items to be added

    • Optional overflowPolicy: OverflowPolicy

      overflow policy to be used

    Returns Promise<Long>

    the sequence number of the last written item from the specified array

capacity

  • capacity(): Promise<Long>

  • Returns Promise<Long>

    capacity of this Ringbuffer

destroy

  • destroy(): Promise<void>

  • Destroys this object cluster-wide. Clears all resources taken for this object.

    Returns Promise<void>

getName

  • getName(): string

  • Returns the unique name of this object.

    Returns string

getPartitionKey

  • getPartitionKey(): string

  • Returns the key of the partition that this DistributedObject is assigned to. For a partitioned data structure, the returned value will not be null, but otherwise undefined.

    Returns string

getServiceName

  • getServiceName(): string

headSequence

  • headSequence(): Promise<Long>

  • Returns the head sequence. The head is the side of the ringbuffer where the oldest items are found.

    If the ringbuffer is empty, the head will be one more than the tail.

    The initial value of the head is 0.

    Returns Promise<Long>

    head sequence of this Ringbuffer

readMany

  • readMany(startSequence: number | Long, minCount: number, maxCount: number): Promise<ReadResultSet<E>>

  • Reads a batch of items from the Ringbuffer. If the number of available items starting at sequence is smaller than maxCount, then this method will not wait for more items to arrive. Instead, available items will be returned.

    If there are fewer items available than minCount, then this call will not return a response until a necessary number of items becomes available.

    If startSequence is smaller than the smallest sequence still available in the Ringbuffer headSequence, then the smallest available sequence will be used as the start sequence, and the minimum/maximum number of items will be attempted to be read from there on.

    If startSequence is bigger than the last available sequence in the Ringbuffer tailSequence, then the last available sequence plus one will be used as the start sequence, and the call will block until further items become available, and it can read at least the minimum number of items.

    throws

    RangeError if startSequence is smaller than 0, or if minCount smaller than 0, or if minCount larger than maxCount, or if maxCount larger than 1000 (to prevent overloading)

    Parameters

    • startSequence: number | Long

      sequence number of the first item to be read.

    • minCount: number

      minimum number of items to be read.

    • maxCount: number

      maximum number of items to be read.

    Returns Promise<ReadResultSet<E>>

readOne

  • readOne(sequence: number | Long): Promise<E>

  • Reads a single item from this Ringbuffer.

    If the sequence is equal to the current tail sequence plus one, this call will not return a response until an item is added. If it is more than that, an error will be thrown.

    Unlike queue's take, this method does not remove an item from the Ringbuffer. This means that the same item can be read by multiple processes.

    throws

    RangeError if sequence is: smaller than 0, or smaller than headSequence, or greater than tailSequence + 1

    Parameters

    • sequence: number | Long

      the sequence number of the item to read

    Returns Promise<E>

    the item that was read

remainingCapacity

  • remainingCapacity(): Promise<Long>

  • Returns the remaining capacity of this ringbuffer.

    The returned value could be stale as soon as it is returned.

    If the time-to-live was NOT set in the configuration, the remaining capacity will always be equal to the capacity.

    Returns Promise<Long>

    remaining capacity of this Ringbuffer

size

  • size(): Promise<Long>

  • Returns the number of the items in this Ringbuffer.

    If time-to-live was not configured for this ringbuffer, the size will always be equal to the capacity after the first loop is completed around the ring. This is because no items are getting removed and are overwritten instead.

    Returns Promise<Long>

    size of this Ringbuffer

tailSequence

  • tailSequence(): Promise<Long>

  • Returns the tail sequence. The tail is the side of the Ringbuffer at which the items are added.

    The initial value of the tail sequence is -1.

    Returns Promise<Long>

    tail sequence of this Ringbuffer

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