Author: reschke
Date: Sat Mar 22 09:01:44 2014
New Revision: 1580185
URL: http://svn.apache.org/r1580185
Log:
OAK-1564 - ClockTest on Windows fails: try to determine that actual (and
current) granularity of System.currentTimeMillis() in order to have the correct
test expectations
Modified:
jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java
Modified:
jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java
URL:
http://svn.apache.org/viewvc/jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java?rev=1580185&r1=1580184&r2=1580185&view=diff
==============================================================================
---
jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java
(original)
+++
jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java
Sat Mar 22 09:01:44 2014
@@ -18,12 +18,9 @@ package org.apache.jackrabbit.oak.stats;
import static junit.framework.Assert.assertTrue;
-import java.util.ArrayList;
-import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
-import org.junit.Ignore;
import org.junit.Test;
public class ClockTest {
@@ -32,29 +29,17 @@ public class ClockTest {
* Helper for checking how accurate the system clock is.
*/
public static void main(String[] args) {
- List<Long> values = new ArrayList<Long>();
- long end = System.currentTimeMillis() + 10000; // 10 seconds
- long last = System.currentTimeMillis();
- long current = last;
-
- do {
- current = System.currentTimeMillis();
- if (current != last && current != last + 1) {
- values.add(current);
- }
- last = current;
- } while (current < end);
- for (int i = 1; i < values.size(); i++) {
- System.out.println(values.get(i) + " " + (values.get(i) -
values.get(i - 1)));
- }
+ System.out.println("average clock granularity: " +
getAverageClockGranularity());
}
@Test
- @Ignore("OAK-1564") // FIXME OAK-1564 ClockTest on Windows fails
public void testClockDrift() throws InterruptedException {
ScheduledExecutorService executor =
Executors.newSingleThreadScheduledExecutor();
- final long limit = 20;
+ final long granularity = getAverageClockGranularity();
+ final long limit = (2 * granularity) / 1000; // allow a drift twice as
high
+ final String diag = "(estimated limit was " + limit + "ms, measured
granularity was " + ( granularity / 1000f) + "ms)";
+
try {
Clock[] clocks = new Clock[] {
Clock.SIMPLE,
@@ -64,14 +49,14 @@ public class ClockTest {
for (Clock clock : clocks) {
long drift = clock.getTime() - System.currentTimeMillis();
- assertTrue("unexpected drift: " + Math.abs(drift) + " (limit "
+ limit +")", Math.abs(drift) < limit); // Windows can have 15ms gaps
+ assertTrue("unexpected drift: " + Math.abs(drift) + "ms " +
diag, Math.abs(drift) <= limit);
}
Thread.sleep(100);
for (Clock clock : clocks) {
long drift = clock.getTime() - System.currentTimeMillis();
- assertTrue("unexpected drift: " + Math.abs(drift) + " (limit "
+ limit +")", Math.abs(drift) < limit);
+ assertTrue("unexpected drift: " + Math.abs(drift) + "ms " +
diag, Math.abs(drift) <= limit);
}
} finally {
executor.shutdown();
@@ -102,4 +87,29 @@ public class ClockTest {
}
}
+ /**
+ * On some systems (for instance Windows), the granularity of {@link
System.currentTimeMillis} depends
+ * on system-wide settings that can change depending on what applications
are running
+ * (see, for instance <a
href="http://www.lifehacker.com.au/2009/05/hidden-windows-7-tool-troubleshoots-sleep-mode-problems/";>http://www.lifehacker.com.au/2009/05/hidden-windows-7-tool-troubleshoots-sleep-mode-problems/</a>).
+ * This method tries to measure the granularity.
+ * @return average granularity of {@link System.currentTimeMillis} in
1/1000 of milliseconds
+ */
+ private static long getAverageClockGranularity() {
+ long sum = 0;
+ int samples = 20; // number of samples to take
+ long last = System.currentTimeMillis();
+
+ for (int i = 0; i < samples; i++) {
+ long now = System.currentTimeMillis();
+ while (now == last) {
+ // busy-wait until return value changes
+ now = System.currentTimeMillis();
+ }
+ sum += (now - last); // add the actual difference
+ last = now;
+ }
+
+ // return average in 1/1000ms
+ return (sum * 1000) / samples;
+ }
}
\ No newline at end of file
