J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.jvmstat.perfdata.monitor; |
| 27 | |
| 28 | import java.util.*; |
| 29 | |
| 30 | /** |
| 31 | * Utility methods for use with {@link CountedTimerTask} instances. |
| 32 | * |
| 33 | * @author Brian Doherty |
| 34 | * @since 1.5 |
| 35 | */ |
| 36 | public class CountedTimerTaskUtils { |
| 37 | |
| 38 | private static final boolean DEBUG = false; |
| 39 | |
| 40 | /** |
| 41 | * Reschedule a CountedTimeTask at a different interval. Probably not |
| 42 | * named correctly. This method cancels the old task and computes the |
| 43 | * delay for starting the new task based on the new interval and the |
| 44 | * time at which the old task was last executed. |
| 45 | * |
| 46 | * @param timer the Timer for the task |
| 47 | * @param oldTask the old Task |
| 48 | * @param newTask the new Task |
| 49 | * @param oldInterval the old interval; use for debugging output |
| 50 | * purposes only. |
| 51 | * @param newInterval scheduling interval in milliseconds |
| 52 | */ |
| 53 | public static void reschedule(Timer timer, CountedTimerTask oldTask, |
| 54 | CountedTimerTask newTask, int oldInterval, |
| 55 | int newInterval) { |
| 56 | |
| 57 | long now = System.currentTimeMillis(); |
| 58 | long lastRun = oldTask.scheduledExecutionTime(); |
| 59 | long expired = now - lastRun; |
| 60 | |
| 61 | if (DEBUG) { |
| 62 | System.err.println("computing timer delay: " |
| 63 | + " oldInterval = " + oldInterval |
| 64 | + " newInterval = " + newInterval |
| 65 | + " samples = " + oldTask.executionCount() |
| 66 | + " expired = " + expired); |
| 67 | } |
| 68 | |
| 69 | /* |
| 70 | * check if original task ever ran - if not, then lastRun is |
| 71 | * undefined and we simply set the delay to 0. |
| 72 | */ |
| 73 | long delay = 0; |
| 74 | if (oldTask.executionCount() > 0) { |
| 75 | long remainder = newInterval - expired; |
| 76 | delay = remainder >= 0 ? remainder : 0; |
| 77 | } |
| 78 | |
| 79 | if (DEBUG) { |
| 80 | System.err.println("rescheduling sampler task: interval = " |
| 81 | + newInterval |
| 82 | + " delay = " + delay); |
| 83 | } |
| 84 | |
| 85 | timer.schedule(newTask, delay, newInterval); |
| 86 | } |
| 87 | } |