com.hazelcast.spi.impl.operationexecutor.classic.ScheduleQueue Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2015, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.spi.impl.operationexecutor.classic;
/**
* The ScheduleQueue is a kind of priority queue where 'tasks' are queued for scheduling.
*
* Implementations must support Multiple-Producer Multiple-Consumers scenario as multiple
* {@link GenericOperationThread} share a single queue.
*
* The ScheduledQueue also support priority tasks; so if a task with a priority comes in, than
* that one is taken before any other normal operation is taken.
*
* The ordering between normal tasks will always be FIFO. And the same goes for the ordering between
* priority tasks, but there is no ordering guarantee between priority and normal tasks.
*/
public interface ScheduleQueue {
/**
* Adds an task with normal priority to this queue.
*
* This method is thread safe.
*
* @param task the item to add
* @throws java.lang.NullPointerException if task is null
*/
void add(Object task);
/**
* Adds an task with normal priority to this queue.
*
* This method is thread safe.
*
* @param task the item to add
* @throws java.lang.NullPointerException if task is null
*/
void addUrgent(Object task);
/**
* Takes an item from this queue. If no item is available, the call blocks.
*
* This method should always be called by the same thread.
*
* @return the taken item.
* @throws InterruptedException if the thread is interrupted while waiting.
*/
Object take() throws InterruptedException;
/**
* returns the number of normal operations pending.
*
* This method is thread safe.
*
* This method returns a best effort value and should only be used for monitoring purposes.
*
* @return the number of normal pending operations.
*/
int normalSize();
/**
* returns the number of priority operations pending.
*
* This method is thread safe.
*
* This method returns a best effort value and should only be used for monitoring purposes.
*
* @return the number of priority pending operations.
*/
int prioritySize();
/**
* Returns the total number of pending operations.
*
* This method is thread safe.
*
* This method returns a best effort value and should only be used for monitoring purposes.
*
* @return the total number of pending operations.
*/
int size();
}