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Scheduler of java processes that seeks to optimize the execution of processing tasks by the JVM with minimal threads in order to reduce the overhead of context switching, optimize the utilization of CPU cores, and provide controls to the application over the scheduling of processing tasks.

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/*
 *   Copyright 2015 AML Innovation & Consulting LLC
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements.  See the NOTICE file distributed with
 *   this work for additional information regarding copyright ownership.
 *   The ASF licenses this file to You 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.amlinv.javasched;

import java.util.List;

/**
 * Scheduler - the top-level object for running processes.  Processes are submitted to the scheduler
 * which then starts each process by asking for the first step.  Non-blocking steps are immediately
 * queued for execution on a non- blocking thread executor which runs a small number of threads that
 * are intended to be running non-stop except when there are no non-blocking steps ready for
 * execution.
 *
 * Blocking steps, on the other hand, are queued for execution on the blocking-thread executor which
 * will allocate large numbers of threads, as-needed, to sit and wait for blocking operations to
 * process.  Obviously, it's best to use IOC and asynchronous methods to avoid blocking, but that is
 * beyond the scope of the scheduler itself.
 *
 * Created by art on 12/8/14.
 */
public interface Scheduler {

  /**
   * Start execution of the given process.
   *
   * @param newProcess process to execute.
   * @return execution slip that can be used to watch the progress and status of the process.
   */
  SchedulerProcessExecutionSlip startProcess(SchedulerProcess newProcess);

  /**
   * Retrieve the list of processes currently being scheduled.
   *
   * @return list of the scheduled processes.
   */
  List getProcessList();

  /**
   * Start the scheduler main loop.
   */
  void start();
}