Author: jukka
Date: Thu Mar 13 14:32:48 2014
New Revision: 1577177
URL: http://svn.apache.org/r1577177
Log:
OAK-1535: ClockTest.testClockDrift failures
Increase accuracy of the accurate clock.
Introduce a configurable random noise element to the simple clock.
Remove the accidentally committed &~0xfL test modifier from
System.currentTimeMillis()
Modified:
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/stats/Clock.java
jackrabbit/oak/trunk/oak-core/src/test/java/org/apache/jackrabbit/oak/stats/ClockTest.java
Modified:
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/stats/Clock.java
URL:
http://svn.apache.org/viewvc/jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/stats/Clock.java?rev=1577177&r1=1577176&r2=1577177&view=diff
==============================================================================
---
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/stats/Clock.java
(original)
+++
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/stats/Clock.java
Thu Mar 13 14:32:48 2014
@@ -17,6 +17,7 @@
package org.apache.jackrabbit.oak.stats;
import java.util.Date;
+import java.util.Random;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
@@ -26,6 +27,15 @@ import java.util.concurrent.TimeUnit;
public abstract class Clock {
/**
+ * Maximum amount (in ms) of random noise to include in the time
+ * signal reported by the {@link #SIMPLE} clock. Configurable by the
+ * "simple.clock.noise" system property to make it easier to test
+ * the effect of an inaccurate system clock.
+ */
+ private static final int SIMPLE_CLOCK_NOISE =
+ Integer.getInteger("simple.clock.noise", 0);
+
+ /**
* Millisecond granularity of the {@link #ACCURATE} clock.
* Configurable by the "accurate.clock.granularity" system property
* to make it easier to test the effect of a slow-moving clock on
@@ -123,12 +133,27 @@ public abstract class Clock {
* Simple clock implementation based on {@link System#currentTimeMillis()},
* which is known to be rather slow on some platforms.
*/
- public static Clock SIMPLE = new Clock() {
- @Override
- public long getTime() {
- return System.currentTimeMillis() & ~0xfL;
+ public static Clock SIMPLE = createSimpleClock();
+
+ private static Clock createSimpleClock() {
+ final int noise = SIMPLE_CLOCK_NOISE;
+ if (noise > 0) {
+ return new Clock() {
+ private final Random random = new Random();
+ @Override
+ public synchronized long getTime() {
+ return System.currentTimeMillis() + random.nextInt(noise);
+ }
+ };
+ } else {
+ return new Clock() {
+ @Override
+ public long getTime() {
+ return System.currentTimeMillis();
+ }
+ };
}
- };
+ }
/**
* Accurate clock implementation that uses interval timings from the
@@ -153,16 +178,24 @@ public abstract class Clock {
if (now > ms + SYNC_INTERVAL) {
ms = SIMPLE.getTime();
ns = System.nanoTime();
+ // Check whether the system time jumped ahead or back
+ // from what we'd expect based on the nanosecond interval.
+ // If the jump was small, it was probably caused by low
+ // granularity of the system time. In that case we reduce
+ // the jump to just 0.5ms to smoothen the reported time.
+ // This should still keep clock drift in check as long as
+ // the nanosecond timings drift on average less than 0.5ms
+ // per second.
long jump = ms - now;
- if (jump != 0 && Math.abs(jump) < SYNC_INTERVAL) {
- // currentTimeMillis() jumped a little bit, which was
- // probably caused by its lower granularity instead of
- // an adjustment to system time, so we reduce the jump
- // to just 0.5ms to make the reported time smoother
+ if (0 < jump && jump < 1000) {
+ ms = now;
+ ns -= NS_IN_MS / 2;
+ } else if (0 > jump && jump > -1000) {
+ // Note that the Math.max(..., 0) above will cause the
+ // reported time to stay constant for a while instead
+ // of going backwards because of this.
ms = now;
- ns += Long.signum(jump) * NS_IN_MS / 2;
- } else {
- now = ms;
+ ns += NS_IN_MS / 2;
}
}
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=1577177&r1=1577176&r2=1577177&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
Thu Mar 13 14:32:48 2014
@@ -18,6 +18,8 @@ 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;
@@ -25,6 +27,27 @@ import org.junit.Test;
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)));
+ }
+ }
+
@Test
public void testClockDrift() throws InterruptedException {
ScheduledExecutorService executor =
