| /* |
| * Copyright 2016-present Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.onosproject.store.service; |
| |
| import java.util.Arrays; |
| import java.util.Collection; |
| import java.util.concurrent.CompletableFuture; |
| import java.util.concurrent.Executor; |
| import java.util.function.Consumer; |
| |
| import com.google.common.collect.ImmutableList; |
| |
| /** |
| * Distributed Work Queue primitive. |
| * <p> |
| * Work queue serves as a buffer allowing producers to {@link #addMultiple(Collection) add} tasks and consumers |
| * to {@link #take() take} tasks to process. |
| * <p> |
| * 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 {@link #complete(Collection) 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. |
| * |
| * @param <E> task payload type. |
| */ |
| public interface WorkQueue<E> extends DistributedPrimitive { |
| |
| @Override |
| default DistributedPrimitive.Type primitiveType() { |
| return DistributedPrimitive.Type.WORK_QUEUE; |
| } |
| |
| /** |
| * Adds a collection of tasks to the work queue. |
| * @param items collection of task items |
| * @return future that is completed when the operation completes |
| */ |
| CompletableFuture<Void> addMultiple(Collection<E> items); |
| |
| /** |
| * Picks up multiple tasks from the work queue to work on. |
| * <p> |
| * Tasks that are taken remain invisible to other consumers as long as the consumer stays alive. |
| * If a consumer unexpectedly terminates before {@link #complete(String...) completing} the task, |
| * the task becomes visible again to other consumers to process. |
| * @param maxItems maximum number of items to take from the queue. The actual number of tasks returned |
| * can be at the max this number |
| * @return future for the tasks. The future can be completed with an empty collection if there are no |
| * unassigned tasks in the work queue |
| */ |
| CompletableFuture<Collection<Task<E>>> take(int maxItems); |
| |
| /** |
| * Completes a collection of tasks. |
| * @param taskIds ids of tasks to complete |
| * @return future that is completed when the operation completes |
| */ |
| CompletableFuture<Void> complete(Collection<String> taskIds); |
| |
| /** |
| * Registers a task processing callback to be automatically invoked when new tasks are |
| * added to the work queue. |
| * @param taskProcessor task processing callback |
| * @param parallelism max tasks that can be processed in parallel |
| * @param executor executor to use for processing the tasks |
| * @return future that is completed when the operation completes |
| */ |
| CompletableFuture<Void> registerTaskProcessor(Consumer<E> taskProcessor, |
| int parallelism, |
| Executor executor); |
| |
| /** |
| * Stops automatically processing tasks from work queue. This call nullifies the effect of a |
| * previous {@link #registerTaskProcessor registerTaskProcessor} call. |
| * @return future that is completed when the operation completes |
| */ |
| CompletableFuture<Void> stopProcessing(); |
| |
| /** |
| * Returns work queue statistics. |
| * @return future that is completed with work queue stats when the operation completes |
| */ |
| CompletableFuture<WorkQueueStats> stats(); |
| |
| /** |
| * Completes a collection of tasks. |
| * @param taskIds var arg list of task ids |
| * @return future that is completed when the operation completes |
| */ |
| default CompletableFuture<Void> complete(String... taskIds) { |
| return complete(Arrays.asList(taskIds)); |
| } |
| |
| /** |
| * Adds a single task to the work queue. |
| * @param item task item |
| * @return future that is completed when the operation completes |
| */ |
| default CompletableFuture<Void> addOne(E item) { |
| return addMultiple(ImmutableList.of(item)); |
| } |
| |
| /** |
| * Picks up a single task from the work queue to work on. |
| * <p> |
| * Tasks that are taken remain invisible to other consumers as long as the consumer stays alive. |
| * If a consumer unexpectedly terminates before {@link #complete(String...) completing} the task, |
| * the task becomes visible again to other consumers to process. |
| * @return future for the task. The future can be completed with null, if there are no |
| * unassigned tasks in the work queue |
| */ |
| default CompletableFuture<Task<E>> take() { |
| return this.take(1).thenApply(tasks -> tasks.isEmpty() ? null : tasks.iterator().next()); |
| } |
| } |