Package com.rabbitmq.client.impl

Class WorkPool<K,​W>

  • Type Parameters:
    K - Key -- type of client
    W - Work -- type of work item
    public class WorkPool<K,​W>
extends Object

    This is a generic implementation of the channels specification in Channeling Work, Nov 2010 (channels.pdf). Objects of type K must be registered, with registerKey(K), and then they become clients and a queue of items (type W) is stored for each client.

    Each client has a state which is exactly one of dormant, in progress or ready. Immediately after registration a client is dormant. Items may be (singly) added to (the end of) a client's queue with addWorkItem(Object, Object). If the client is dormant it becomes ready thereby. All other states remain unchanged. The next ready client, together with a collection of its items, may be retrieved with nextWorkBlock(collection,max) (making that client in progress). An in progress client can finish (processing a batch of items) with finishWorkBlock(K). It then becomes either dormant or ready, depending if its queue of work items is empty or no. If a client has items queued, it is either in progress or ready but cannot be both. When work is finished it may be marked ready if there is further work, or dormant if there is not. There is never any work for a dormant client. A client may be unregistered, with unregisterKey(K), which removes the client from all parts of the state, and any queue of items stored with it. All clients may be unregistered with unregisterAllKeys().

    Concurrent Semantics

    This implementation is thread-safe.

    • Constructor Detail

      • WorkPool

        public WorkPool​(int queueingTimeout)

    • Method Detail

      • registerKey

        public void registerKey​(K key)
        Add client key to pool of item queues, with an empty queue. A client is initially dormant. No-op if key already present.
        Parameters:
        key - client to add to pool

      • limit

        public void limit​(K key)

      • unlimit

        public void unlimit​(K key)

      • unregisterKey

        public void unregisterKey​(K key)
        Remove client from pool and from any other state. Has no effect if client already absent.
        Parameters:
        key - of client to unregister

      • unregisterAllKeys

        public void unregisterAllKeys()
        Remove all clients from pool and from any other state.

      • nextWorkBlock

        public K nextWorkBlock​(Collection<W> to,
                       int size)
        Return the next ready client, and transfer a collection of that client's items to process. Mark client in progress. If there is no ready client, return null.
        Parameters:
        to - collection object in which to transfer items
        size - max number of items to transfer
        Returns:
        key of client to whom items belong, or null if there is none.

      • addWorkItem

        public boolean addWorkItem​(K key,
                           W item)
        Add (enqueue) an item for a specific client. No change and returns false if client not registered. If dormant, the client will be marked ready.
        Parameters:
        key - the client to add to the work item to
        item - the work item to add to the client queue
        Returns:
        true if and only if the client is marked ready — as a result of this work item

      • finishWorkBlock

        public boolean finishWorkBlock​(K key)
        Set client no longer in progress. Ignore unknown clients (and return false).
        Parameters:
        key - client that has finished work
        Returns:
        true if and only if client becomes ready
        Throws:
        IllegalStateException - if registered client not in progress