1/*
2 * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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7 * published by the Free Software Foundation.
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11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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22 */
23
24/*
25 * @test
26 * @bug     4530538
27 * @summary Basic unit test of RuntimeMXBean.getUptime()
28 * @author  Alexei Guibadoulline
29 */
30
31import java.lang.management.*;
32
33public class UpTime {
34    static final long DELAY = 5; // Seconds
35    static final long TIMEOUT = 30; // Minutes
36    static final long MULTIPLIER = 1000; // millisecond ticks
37
38    private static final RuntimeMXBean metrics
39        = ManagementFactory.getRuntimeMXBean();
40
41    public static void main(String argv[]) throws Exception {
42        long jvmStartTime = metrics.getStartTime();
43        // this will get an aproximate JVM uptime before starting this test
44        long jvmUptime = System.currentTimeMillis() - jvmStartTime;
45        long systemStartOuter = System_milliTime();
46        long metricsStart = metrics.getUptime();
47        long systemStartInner = System_milliTime();
48
49        // This JVM might have been running for some time if this test runs
50        // in samevm mode.  The sanity check should apply to the test uptime.
51        long testUptime = metricsStart - jvmUptime;
52
53        // If uptime is more than 30 minutes then it looks like a bug in
54        // the method
55        if (testUptime > TIMEOUT * 60 * MULTIPLIER)
56            throw new RuntimeException("Uptime of the JVM is more than 30 "
57                                     + "minutes ("
58                                     + (metricsStart / 60 / MULTIPLIER)
59                                     + " minutes).");
60
61        // Wait for DELAY seconds
62        Object o = new Object();
63        while (System_milliTime() < systemStartInner + DELAY * MULTIPLIER) {
64            synchronized (o) {
65                try {
66                    o.wait(DELAY * 1000);
67                } catch (Exception e) {
68                    e.printStackTrace();
69                    throw e;
70                }
71            }
72        }
73
74        long systemEndInner = System_milliTime();
75        long metricsEnd = metrics.getUptime();
76        long systemEndOuter = System_milliTime();
77
78        long systemDifferenceInner = systemEndInner - systemStartInner;
79        long systemDifferenceOuter = systemEndOuter - systemStartOuter;
80        long metricsDifference = metricsEnd - metricsStart;
81
82        // Check the flow of time in RuntimeMXBean.getUptime(). See the
83        // picture below.
84        // The measured times can be off by 1 due to conversions from
85        // nanoseconds to milliseconds, using different channels to read the
86        // HR timer and rounding error. Bigger difference will make the test
87        // fail.
88        if (metricsDifference - systemDifferenceInner < -1)
89            throw new RuntimeException("Flow of the time in "
90                                     + "RuntimeMXBean.getUptime() ("
91                                     + metricsDifference + ") is slower than "
92                                     + " in system (" + systemDifferenceInner
93                                     + ")");
94        if (metricsDifference - systemDifferenceOuter > 1)
95            throw new RuntimeException("Flow of the time in "
96                                     + "RuntimeMXBean.getUptime() ("
97                                     + metricsDifference + ") is faster than "
98                                     + "in system (" + systemDifferenceOuter
99                                     + ")");
100
101        System.out.println("Test passed.");
102    }
103
104    private static long System_milliTime() {
105        return System.nanoTime() / 1000000; // nanoseconds / milliseconds;
106    }
107}
108
109/*
110
111   A picture to describe the second testcase that checks the flow of time in
112   RuntimeMXBean.getUptime()
113
114
115   start
116             o1  u1  i1    Sleep for DELAY minutes    i2  u2  o2
117     |-------|---|---|--------------------------------|---|---|---------------> time
118
119
120   The following inequality (checked by the test) must always be true:
121
122       o2-o1 >= u2-u1 >= i2-i1
123
124   In the test:
125
126   i1 - systemStartInner
127   i2 - systemEndInner
128   o1 - systemStartOuter
129   o2 - systemEndOuter
130   u1 - metricsStart
131   u2 - metricsEnd
132
133*/
134