org.onosproject.store.service.WorkQueue Maven / Gradle / Ivy
/*
* Copyright 2016-present Open Networking Foundation
*
* 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.
*
* Work queue serves as a buffer allowing producers to {@link #addMultiple(Collection) add} tasks and consumers
* to {@link #take() 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 {@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 task payload type.
*/
public interface WorkQueue 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 addMultiple(Collection items);
/**
* 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 {@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>> 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 complete(Collection 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 registerTaskProcessor(Consumer 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 stopProcessing();
/**
* Returns work queue statistics.
* @return future that is completed with work queue stats when the operation completes
*/
CompletableFuture 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 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 addOne(E item) {
return addMultiple(ImmutableList.of(item));
}
/**
* 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 {@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> take() {
return this.take(1).thenApply(tasks -> tasks.isEmpty() ? null : tasks.iterator().next());
}
}