Package org.onosproject.store.service

Interface WorkQueue<E>

  • Type Parameters:
    E - task payload type.
    All Superinterfaces:
    DistributedPrimitive
    public interface WorkQueue<E>
extends DistributedPrimitive
    Distributed Work Queue primitive.

    Work queue serves as a buffer allowing producers to add tasks and consumers to take tasks to process.

    In the system each task is tracked via its unique task identifier which is returned when a task is taken. Work queue guarantees that a task can be taken by only one consumer at a time. Once it finishes processing a consumer must invoke the complete method to mark the task(s) as completed. Tasks thus completed are removed from the queue. If a consumer unexpectedly terminates before it can complete all its tasks are returned back to the queue so that other consumers can pick them up. Since there is a distinct possibility that tasks could be processed more than once (under failure conditions), care should be taken to ensure task processing logic is idempotent.

    • Method Detail

      • addMultiple

        CompletableFuture<Void> addMultiple​(Collection<E> items)
        Adds a collection of tasks to the work queue.
        Parameters:
        items - collection of task items
        Returns:
        future that is completed when the operation completes

      • take

        CompletableFuture<Collection<Task<E>>> take​(int maxItems)
        Picks up multiple tasks from the work queue to work on.

        Tasks that are taken remain invisible to other consumers as long as the consumer stays alive. If a consumer unexpectedly terminates before completing the task, the task becomes visible again to other consumers to process.

        Parameters:
        maxItems - maximum number of items to take from the queue. The actual number of tasks returned can be at the max this number
        Returns:
        future for the tasks. The future can be completed with an empty collection if there are no unassigned tasks in the work queue

      • complete

        CompletableFuture<Void> complete​(Collection<String> taskIds)
        Completes a collection of tasks.
        Parameters:
        taskIds - ids of tasks to complete
        Returns:
        future that is completed when the operation completes

      • registerTaskProcessor

        CompletableFuture<Void> registerTaskProcessor​(Consumer<E> taskProcessor,
                                              int parallelism,
                                              Executor executor)
        Registers a task processing callback to be automatically invoked when new tasks are added to the work queue.
        Parameters:
        taskProcessor - task processing callback
        parallelism - max tasks that can be processed in parallel
        executor - executor to use for processing the tasks
        Returns:
        future that is completed when the operation completes

      • stopProcessing

        CompletableFuture<Void> stopProcessing()
        Stops automatically processing tasks from work queue. This call nullifies the effect of a previous registerTaskProcessor call.
        Returns:
        future that is completed when the operation completes

      • stats

        CompletableFuture<WorkQueueStats> stats()
        Returns work queue statistics.
        Returns:
        future that is completed with work queue stats when the operation completes

      • complete

        default CompletableFuture<Void> complete​(String... taskIds)
        Completes a collection of tasks.
        Parameters:
        taskIds - var arg list of task ids
        Returns:
        future that is completed when the operation completes

      • addOne

        default CompletableFuture<Void> addOne​(E item)
        Adds a single task to the work queue.
        Parameters:
        item - task item
        Returns:
        future that is completed when the operation completes

      • take

        default CompletableFuture<Task<E>> take()
        Picks up a single task from the work queue to work on.

        Tasks that are taken remain invisible to other consumers as long as the consumer stays alive. If a consumer unexpectedly terminates before completing the task, the task becomes visible again to other consumers to process.

        Returns:
        future for the task. The future can be completed with null, if there are no unassigned tasks in the work queue