001// Copyright 2011 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.ioc.services.cron;
016
017/**
018 * Used with {@link PeriodicExecutor} to control the schedule for when jobs execute.
019 */
020public interface Schedule
021{
022    /**
023     * For a newly created job, what is the start time for the job.  Often, the current clock time is returned, to start
024     * a job as soon as possible.
025     *
026     * @return start time for new job, in system clock millis
027     */
028    long firstExecution();
029
030    /**
031     * Computes the next execution time for a job.
032     *
033     * @param previousExecution time of previous execution (in system clock millis)
034     * @return time of next execution (in system clock millis)
035     */
036    long nextExecution(long previousExecution);
037}