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fixed StaticStrideScheduler looping too many times (#10370)

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Tony An 2023-07-13 10:24:07 -07:00 committed by GitHub
parent 78cf1c39cf
commit 37351c690c
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2 changed files with 17 additions and 16 deletions
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13
xds/src/main/java/io/grpc/xds/WeightedRoundRobinLoadBalancer.java
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@ -350,7 +350,6 @@ final class WeightedRoundRobinLoadBalancer extends RoundRobinLoadBalancer {
@VisibleForTesting @VisibleForTesting
static final class StaticStrideScheduler { static final class StaticStrideScheduler {
private final short[] scaledWeights; private final short[] scaledWeights;
private final int sizeDivisor;
private final AtomicInteger sequence; private final AtomicInteger sequence;
private static final int K_MAX_WEIGHT = 0xFFFF; private static final int K_MAX_WEIGHT = 0xFFFF;
@ -373,7 +372,7 @@ final class WeightedRoundRobinLoadBalancer extends RoundRobinLoadBalancer {
if (numWeightedChannels > 0) { if (numWeightedChannels > 0) {
meanWeight = (short) Math.round(scalingFactor * sumWeight / numWeightedChannels); meanWeight = (short) Math.round(scalingFactor * sumWeight / numWeightedChannels);
} else { } else {
meanWeight = 1; meanWeight = (short) Math.round(scalingFactor);
} }
// scales weights s.t. max(weights) == K_MAX_WEIGHT, meanWeight is scaled accordingly // scales weights s.t. max(weights) == K_MAX_WEIGHT, meanWeight is scaled accordingly
@ -387,7 +386,6 @@ final class WeightedRoundRobinLoadBalancer extends RoundRobinLoadBalancer {
} }
this.scaledWeights = scaledWeights; this.scaledWeights = scaledWeights;
this.sizeDivisor = numChannels;
this.sequence = new AtomicInteger(random.nextInt()); this.sequence = new AtomicInteger(random.nextInt());
} }
@ -433,15 +431,18 @@ final class WeightedRoundRobinLoadBalancer extends RoundRobinLoadBalancer {
* an offset that varies per backend index is also included to the calculation. * an offset that varies per backend index is also included to the calculation.
*/ */
int pick() { int pick() {
int i = 0;
while (true) { while (true) {
i++;
long sequence = this.nextSequence(); long sequence = this.nextSequence();
int backendIndex = (int) (sequence % this.sizeDivisor); int backendIndex = (int) (sequence % scaledWeights.length);
long generation = sequence / this.sizeDivisor; long generation = sequence / scaledWeights.length;
int weight = Short.toUnsignedInt(this.scaledWeights[backendIndex]); int weight = Short.toUnsignedInt(scaledWeights[backendIndex]);
long offset = (long) K_MAX_WEIGHT / 2 * backendIndex; long offset = (long) K_MAX_WEIGHT / 2 * backendIndex;
if ((weight * generation + offset) % K_MAX_WEIGHT < K_MAX_WEIGHT - weight) { if ((weight * generation + offset) % K_MAX_WEIGHT < K_MAX_WEIGHT - weight) {
continue; continue;
} }
assert i <= scaledWeights.length : "scheduler has more than one pass through";
return backendIndex; return backendIndex;
} }
} }

20
xds/src/test/java/io/grpc/xds/WeightedRoundRobinLoadBalancerTest.java
View File

@ -330,11 +330,11 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
assertThat(pickCount.size()).isEqualTo(3); assertThat(pickCount.size()).isEqualTo(3);
assertThat(Math.abs(pickCount.get(weightedSubchannel1) / 10000.0 - subchannel1PickRatio)) assertThat(Math.abs(pickCount.get(weightedSubchannel1) / 10000.0 - subchannel1PickRatio))
.isAtMost(0.001); .isAtMost(0.0001);
assertThat(Math.abs(pickCount.get(weightedSubchannel2) / 10000.0 - subchannel2PickRatio )) assertThat(Math.abs(pickCount.get(weightedSubchannel2) / 10000.0 - subchannel2PickRatio ))
.isAtMost(0.001); .isAtMost(0.0001);
assertThat(Math.abs(pickCount.get(weightedSubchannel3) / 10000.0 - subchannel3PickRatio )) assertThat(Math.abs(pickCount.get(weightedSubchannel3) / 10000.0 - subchannel3PickRatio ))
.isAtMost(0.001); .isAtMost(0.0001);
} }
@Test @Test
@ -751,12 +751,12 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
assertThat(pickCount.size()).isEqualTo(3); assertThat(pickCount.size()).isEqualTo(3);
assertThat(Math.abs(pickCount.get(weightedSubchannel1) / 1000.0 - 4.0 / 9)) assertThat(Math.abs(pickCount.get(weightedSubchannel1) / 1000.0 - 4.0 / 9))
.isAtMost(0.002); .isAtMost(0.001);
assertThat(Math.abs(pickCount.get(weightedSubchannel2) / 1000.0 - 2.0 / 9)) assertThat(Math.abs(pickCount.get(weightedSubchannel2) / 1000.0 - 2.0 / 9))
.isAtMost(0.002); .isAtMost(0.001);
// subchannel3's weight is average of subchannel1 and subchannel2 // subchannel3's weight is average of subchannel1 and subchannel2
assertThat(Math.abs(pickCount.get(weightedSubchannel3) / 1000.0 - 3.0 / 9)) assertThat(Math.abs(pickCount.get(weightedSubchannel3) / 1000.0 - 3.0 / 9))
.isAtMost(0.002); .isAtMost(0.001);
} }
@Test @Test
@ -947,7 +947,7 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
for (int i = 0; i < 3; i++) { for (int i = 0; i < 3; i++) {
assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight)) assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight))
.isAtMost(0.01); .isAtMost(0.001);
} }
} }
@ -964,7 +964,7 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
for (int i = 0; i < 3; i++) { for (int i = 0; i < 3; i++) {
assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight)) assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight))
.isAtMost(0.01); .isAtMost(0.001);
} }
} }
@ -981,7 +981,7 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
for (int i = 0; i < 2; i++) { for (int i = 0; i < 2; i++) {
assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight)) assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight))
.isAtMost(0.01); .isAtMost(0.001);
} }
} }
@ -1015,7 +1015,7 @@ public class WeightedRoundRobinLoadBalancerTest {
} }
for (int i = 0; i < 8; i++) { for (int i = 0; i < 8; i++) {
assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight)) assertThat(Math.abs(pickCount.getOrDefault(i, 0) / 1000.0 - weights[i] / totalWeight))
.isAtMost(0.01); .isAtMost(0.004);
} }
} }