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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.search.dispatch;
import com.yahoo.search.dispatch.LoadBalancer.AdaptiveScheduler;
import com.yahoo.search.dispatch.LoadBalancer.BestOfRandom2;
import com.yahoo.search.dispatch.LoadBalancer.GroupStatus;
import com.yahoo.search.dispatch.searchcluster.Group;
import com.yahoo.search.dispatch.searchcluster.Node;
import org.junit.jupiter.api.Test;
import java.time.Duration;
import java.time.Instant;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Random;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
/**
* @author ollivir
*/
public class LoadBalancerTest {
private static final double delta = 0.0000001;
@Test
void requireThatLoadBalancerServesSingleNodeSetups() {
Node n1 = new Node("test", 0, "test-node1", 0);
LoadBalancer lb = new LoadBalancer(List.of(new Group(0, List.of(n1))), LoadBalancer.Policy.ROUNDROBIN);
Optional<Group> grp = lb.takeGroup(null);
Group group = grp.orElseThrow(() -> {
throw new IllegalStateException("Expected a SearchCluster.Group");
});
assertEquals(1, group.nodes().size());
}
@Test
void requireThatLoadBalancerServesMultiGroupSetups() {
Node n1 = new Node("test", 0, "test-node1", 0);
Node n2 = new Node("test", 1, "test-node2", 1);
LoadBalancer lb = new LoadBalancer(List.of(new Group(0, List.of(n1)), new Group(1,List.of(n2))), LoadBalancer.Policy.ROUNDROBIN);
Optional<Group> grp = lb.takeGroup(null);
Group group = grp.orElseThrow(() -> {
throw new IllegalStateException("Expected a SearchCluster.Group");
});
assertEquals(1, group.nodes().size());
}
@Test
void requireThatLoadBalancerServesClusteredGroups() {
Node n1 = new Node("test", 0, "test-node1", 0);
Node n2 = new Node("test", 1, "test-node2", 0);
Node n3 = new Node("test", 0, "test-node3", 1);
Node n4 = new Node("test", 1, "test-node4", 1);
LoadBalancer lb = new LoadBalancer(List.of(new Group(0, List.of(n1,n2)), new Group(1,List.of(n3,n4))), LoadBalancer.Policy.ROUNDROBIN);
Optional<Group> grp = lb.takeGroup(null);
assertTrue(grp.isPresent());
}
@Test
void requireThatLoadBalancerReturnsDifferentGroups() {
Node n1 = new Node("test", 0, "test-node1", 0);
Node n2 = new Node("test", 1, "test-node2", 1);
LoadBalancer lb = new LoadBalancer(List.of(new Group(0, List.of(n1)), new Group(1,List.of(n2))), LoadBalancer.Policy.ROUNDROBIN);
// get first group
Optional<Group> grp = lb.takeGroup(null);
Group group = grp.get();
int id1 = group.id();
// release allocation
lb.releaseGroup(group, true, RequestDuration.of(Duration.ofMillis(1)));
// get second group
grp = lb.takeGroup(null);
group = grp.get();
assertNotEquals(id1, group.id());
}
@Test
void requireCorrectAverageSearchTimeDecay() {
AdaptiveScheduler.DecayByRequests decayer = new AdaptiveScheduler.DecayByRequests(0, Duration.ofSeconds(1));
GroupStatus gs = newGroupStatus(1);
gs.setDecayer(decayer);
updateSearchTime(gs, RequestDuration.of(Duration.ofSeconds(1)));
assertEquals(Duration.ofSeconds(1), decayer.averageSearchTime());
updateSearchTime(gs, RequestDuration.of(Duration.ofSeconds(2)));
assertEquals(Duration.ofNanos(1023255813), decayer.averageSearchTime());
updateSearchTime(gs, RequestDuration.of(Duration.ofSeconds(2)));
assertEquals(Duration.ofNanos(1045454545), decayer.averageSearchTime());
updateSearchTime(gs, RequestDuration.of(Duration.ofMillis(100)));
updateSearchTime(gs, RequestDuration.of(Duration.ofMillis(100)));
updateSearchTime(gs, RequestDuration.of(Duration.ofMillis(100)));
updateSearchTime(gs, RequestDuration.of(Duration.ofMillis(100)));
assertEquals(Duration.ofNanos(966666666), decayer.averageSearchTime());
for (int i = 0; i < 10000; i++) {
updateSearchTime(gs, RequestDuration.of(Duration.ofSeconds(1)));
}
assertEquals(Duration.ofNanos(999999812), decayer.averageSearchTime());
updateSearchTime(gs, RequestDuration.of(Duration.ofMillis(100)));
assertEquals(Duration.ofNanos(999099812), decayer.averageSearchTime());
for (int i = 0; i < 10000; i++) {
updateSearchTime(gs, RequestDuration.of(Duration.ZERO));
}
assertEquals(Duration.ofNanos(1045087), decayer.averageSearchTime());
}
private Map<Integer, GroupStatus> createScoreBoard(int count) {
Map<Integer, GroupStatus> scoreboard = new HashMap<>();
for (int i = 0; i < count; i++) {
GroupStatus gs = newGroupStatus(i);
scoreboard.put(gs.groupId(), gs);
}
return scoreboard;
}
@Test
void requireEqualDistributionInFlatWeightListWithAdaptiveScheduler() {
Random seq = sequence(0.0, 0.1, 0.2, 0.39, 0.4, 0.6, 0.8, 0.99999);
AdaptiveScheduler sched = new AdaptiveScheduler(AdaptiveScheduler.Type.REQUESTS, seq, createScoreBoard(5));
assertEquals(0, sched.takeNextGroup(null).get().groupId());
assertEquals(0, sched.takeNextGroup(null).get().groupId());
assertEquals(1, sched.takeNextGroup(null).get().groupId());
assertEquals(1, sched.takeNextGroup(null).get().groupId());
assertEquals(2, sched.takeNextGroup(null).get().groupId());
assertEquals(3, sched.takeNextGroup(null).get().groupId());
assertEquals(4, sched.takeNextGroup(null).get().groupId());
assertEquals(4, sched.takeNextGroup(null).get().groupId());
}
@Test
void requireThatAdaptiveSchedulerObeysWeights() {
var scoreboard = createScoreBoard(5);
Random seq = sequence(0.0, 0.4379, 0.4380, 0.6569, 0.6570, 0.8029, 0.8030, 0.9124, 0.9125);
AdaptiveScheduler sched = new AdaptiveScheduler(AdaptiveScheduler.Type.REQUESTS, seq, scoreboard);
int i = 0;
for (GroupStatus gs : scoreboard.values()) {
gs.setDecayer(new AdaptiveScheduler.DecayByRequests(1, Duration.ofMillis((long)(0.1 * (i + 1)*1000.0))));
i++;
}
assertEquals(0, sched.takeNextGroup(null).get().groupId());
assertEquals(0, sched.takeNextGroup(null).get().groupId());
assertEquals(1, sched.takeNextGroup(null).get().groupId());
assertEquals(1, sched.takeNextGroup(null).get().groupId());
assertEquals(2, sched.takeNextGroup(null).get().groupId());
assertEquals(2, sched.takeNextGroup(null).get().groupId());
assertEquals(3, sched.takeNextGroup(null).get().groupId());
assertEquals(3, sched.takeNextGroup(null).get().groupId());
assertEquals(4, sched.takeNextGroup(null).get().groupId());
}
private static GroupStatus allocate(GroupStatus gs) {
gs.allocate();
return gs;
}
@Test
void requireBestOfRandom2Scheduler() {
Random seq = sequence(
0.1, 0.125,
0.1, 0.125,
0.1, 0.125,
0.1, 0.125,
0.1, 0.375,
0.9, 0.125,
0.9, 0.125,
0.9, 0.125
);
BestOfRandom2 sched = new BestOfRandom2(seq, createScoreBoard(5));
assertEquals(0, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(1, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(0, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(1, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(2, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(4, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(4, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(4, allocate(sched.takeNextGroup(null).get()).groupId());
assertEquals(0, allocate(sched.takeNextGroup(null).get()).groupId());
}
private static int countRequestsToReach90p(Duration timeBetweenSample, Duration searchTime) {
double p90 = 0.9*searchTime.toMillis()/1000.0;
GroupStatus.Decayer decayer = new AdaptiveScheduler.DecayByTime(Duration.ofMillis(1), RequestDuration.of(Instant.EPOCH, Duration.ZERO));
int requests = 0;
Instant start = Instant.EPOCH;
while (decayer.averageCost() < p90) {
decayer.decay(RequestDuration.of(start, searchTime));
start = start.plus(timeBetweenSample);
requests++;
}
return requests;
}
@Test
public void requireDecayByTimeToDependOnlyOnTime() {
GroupStatus.Decayer decayer = new AdaptiveScheduler.DecayByTime(Duration.ofMillis(2), RequestDuration.of(Instant.EPOCH, Duration.ZERO));
assertEquals(0.002, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(1000), Duration.ofMillis(10)));
assertEquals(0.003344426, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(2000), Duration.ofMillis(10)));
assertEquals(0.004453688, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(3000), Duration.ofMillis(10)));
assertEquals(0.005378073, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(3100), Duration.ofMillis(10)));
assertEquals(0.005468700, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(3100), Duration.ofMillis(10)));
assertEquals(0.005468700, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(3000), Duration.ofMillis(10)));
assertEquals(0.005557549, decayer.averageCost(), delta);
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(5000), Duration.ofMillis(10)));
assertEquals(0.006826820, decayer.averageCost(), delta);
assertEquals(112, countRequestsToReach90p(Duration.ofMillis(100), Duration.ofMillis(10)));
assertEquals(57, countRequestsToReach90p(Duration.ofMillis(200), Duration.ofMillis(10)));
assertEquals(14, countRequestsToReach90p(Duration.ofMillis(1000), Duration.ofMillis(10)));
}
@Test
public void requireDecayByTimeToNotJumpTooFar() {
AdaptiveScheduler.DecayByTime decayer = new AdaptiveScheduler.DecayByTime(Duration.ofMillis(2), RequestDuration.of(Instant.EPOCH, Duration.ZERO));
assertEquals(0.002, decayer.averageCost(), delta);
assertEquals(Duration.ofMillis(2), decayer.averageSearchTime());
decayer.decay(RequestDuration.of(Instant.ofEpochMilli(10000), Duration.ofMillis(10)));
assertEquals(0.007335110, decayer.averageCost(), delta);
assertEquals(Duration.ofNanos(7335109), decayer.averageSearchTime());
}
private static void updateSearchTime(GroupStatus gs, RequestDuration time) {
gs.allocate();
gs.release(true, time);
}
private GroupStatus newGroupStatus(int id) {
Group dummyGroup = new Group(id, Collections.emptyList()) {
@Override
public boolean hasSufficientCoverage() {
return true;
}
};
return new GroupStatus(dummyGroup);
}
private Random sequence(double... values) {
return new Random() {
private int index = 0;
@Override
public double nextDouble() {
double retv = values[index];
index++;
if (index >= values.length) {
index = 0;
}
return retv;
}
@Override
public int nextInt(int bound) {
return (int)(nextDouble() * bound);
}
};
}
}
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