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fix backoff calucuration #245

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This commit is contained in:
nkzawa
2015-12-14 11:43:44 +09:00
parent fc3002237b
commit 8c29b2ef9c
2 changed files with 29 additions and 15 deletions
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18
src/main/java/io/socket/backo/Backoff.java
View File

@@ -1,5 +1,8 @@
package io.socket.backo;
import java.math.BigDecimal;
import java.math.BigInteger;
public class Backoff {
private long ms = 100;
@@ -11,17 +14,16 @@ public class Backoff {
public Backoff() {}
public long duration() {
long ms = this.ms * (long) Math.pow(this.factor, this.attempts++);
BigInteger ms = BigInteger.valueOf(this.ms)
.multiply(BigInteger.valueOf(this.factor).pow(this.attempts++));
if (jitter != 0.0) {
double rand = Math.random();
int deviation = (int) Math.floor(rand * this.jitter * ms);
ms = (((int) Math.floor(rand * 10)) & 1) == 0 ? ms - deviation : ms + deviation;
BigInteger deviation = BigDecimal.valueOf(rand)
.multiply(BigDecimal.valueOf(jitter))
.multiply(new BigDecimal(ms)).toBigInteger();
ms = (((int) Math.floor(rand * 10)) & 1) == 0 ? ms.subtract(deviation) : ms.add(deviation);
}
if (ms < this.ms) {
// overflow happened
ms = Long.MAX_VALUE;
}
return Math.min(ms, this.max);
return ms.min(BigInteger.valueOf(this.max)).longValue();
}
public void reset() {

26
src/test/java/io/socket/backo/BackoffTest.java
View File

@@ -2,6 +2,9 @@ package io.socket.backo;
import org.junit.Test;
import java.math.BigDecimal;
import java.math.BigInteger;
import static org.junit.Assert.assertTrue;
public class BackoffTest {
@@ -22,14 +25,23 @@ public class BackoffTest {
@Test
public void durationOverflow() {
Backoff b = new Backoff();
b.setMin(100);
b.setMax(10000);
b.setJitter(1.0);
for (int i = 0; i < 10; i++) {
Backoff b = new Backoff();
b.setMin(100);
b.setMax(10000);
b.setJitter(0.5);
for (int i = 0; i < 100; i++) {
long duration = b.duration();
assertTrue(100 <= duration && duration <= 10000);
// repeats to make it overflow (a long can have 2 ** 63 - 1)
for (int j = 0; j < 100; j++) {
BigInteger ms = BigInteger.valueOf(100).multiply(BigInteger.valueOf(2).pow(j));
BigInteger deviation = new BigDecimal(ms).multiply(BigDecimal.valueOf(0.5)).toBigInteger();
BigInteger duration = BigInteger.valueOf(b.duration());
BigInteger min = ms.subtract(deviation).min(BigInteger.valueOf(10000));
BigInteger max = ms.add(deviation).min(BigInteger.valueOf(10001));
assertTrue(min + " <= " + duration + " < " + max,
min.compareTo(duration) <= 0 && max.compareTo(duration) == 1);
}
}
}
}