CB-518: weighted placement policy for worker spawns
This commit is contained in:
Dai Ha
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package dev.ltms.bridged.placement;
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import org.junit.jupiter.api.Test;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.function.Function;
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import static org.junit.jupiter.api.Assertions.*;
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/**
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* Unit tests for the placement policies. They run with no herdr and no launcher — pure selection
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* logic exercised through the descriptor type so CB-308 host expansion will not need to rewrite
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* these assertions.
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*/
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class PlacementPolicyTest {
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private static Function<String, Integer> noSessions() {
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return name -> 0;
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}
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private static PlacementContext ctx(List<PlacementCandidate> candidates,
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Function<String, Integer> liveCount,
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Set<String> unreachable) {
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return new PlacementContext("b", candidates, liveCount, unreachable);
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}
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private static PlacementContext ctx(List<PlacementCandidate> candidates,
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Function<String, Integer> liveCount) {
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return ctx(candidates, liveCount, Set.of());
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}
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@Test
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void fixedReturnsDefaultEvenIfOtherProfilesExist() {
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PlacementPolicy policy = PlacementPolicies.fixed();
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PlacementContext ctx = ctx(List.of(
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PlacementCandidate.profile("a"),
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PlacementCandidate.profile("b")), noSessions());
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assertEquals("b", policy.select(ctx).profile());
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}
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@Test
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void fixedFallsBackToFirstCandidateWhenNoDefault() {
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PlacementPolicy policy = PlacementPolicies.fixed();
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PlacementContext ctx = new PlacementContext(null,
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List.of(PlacementCandidate.profile("a"), PlacementCandidate.profile("b")),
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noSessions(), Set.of());
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assertEquals("a", policy.select(ctx).profile());
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}
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@Test
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void fixedThrowsWhenNoProfilesAndNoDefault() {
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PlacementPolicy policy = PlacementPolicies.fixed();
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PlacementContext ctx = new PlacementContext(null, List.of(), noSessions(), Set.of());
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assertThrows(PlacementException.class, () -> policy.select(ctx));
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}
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@Test
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void roundRobinCyclesThroughAvailableProfiles() {
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PlacementPolicy policy = PlacementPolicies.roundRobin();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a"),
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PlacementCandidate.profile("b"),
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PlacementCandidate.profile("c"));
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assertEquals("a", policy.select(ctx(candidates, noSessions())).profile());
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assertEquals("b", policy.select(ctx(candidates, noSessions())).profile());
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assertEquals("c", policy.select(ctx(candidates, noSessions())).profile());
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assertEquals("a", policy.select(ctx(candidates, noSessions())).profile());
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}
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@Test
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void roundRobinSkipsProfilesAtMaxLoad() {
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PlacementPolicy policy = PlacementPolicies.roundRobin();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 1.0f, 2),
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PlacementCandidate.profile("b", 1.0f, null));
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Function<String, Integer> liveCount = Map.of("a", 2)::get;
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for (int i = 0; i < 5; i++) {
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assertEquals("b", policy.select(ctx(candidates, liveCount)).profile());
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}
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}
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@Test
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void roundRobinThrowsWhenAllAtMaxLoad() {
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PlacementPolicy policy = PlacementPolicies.roundRobin();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 1.0f, 1),
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PlacementCandidate.profile("b", 1.0f, 1));
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Function<String, Integer> liveCount = Map.of("a", 1, "b", 1)::get;
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PlacementException e = assertThrows(PlacementException.class,
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() -> policy.select(ctx(candidates, liveCount)));
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assertTrue(e.getMessage().contains("maxLoad"), e.getMessage());
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}
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@Test
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void weightedAlternatesEvenlyWithEqualWeights() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 0.5f, null),
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PlacementCandidate.profile("b", 0.5f, null));
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int a = 0, b = 0;
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for (int i = 0; i < 100; i++) {
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String p = policy.select(ctx(candidates, noSessions())).profile();
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if ("a".equals(p)) a++;
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else if ("b".equals(p)) b++;
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}
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assertEquals(50, a, "equal weights should split 50/50");
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assertEquals(50, b);
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}
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@Test
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void weightedHoldsThreeToOneRatio() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 0.75f, null),
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PlacementCandidate.profile("b", 0.25f, null));
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int a = 0, b = 0;
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for (int i = 0; i < 40; i++) {
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String p = policy.select(ctx(candidates, noSessions())).profile();
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if ("a".equals(p)) a++;
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else if ("b".equals(p)) b++;
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}
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assertEquals(30, a, "0.75/0.25 should yield a 3:1 ratio over a multiple of 4");
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assertEquals(10, b);
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}
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@Test
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void weightedSkipsProfileAtMaxLoad() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 1.0f, 1),
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PlacementCandidate.profile("b", 1.0f, null));
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Function<String, Integer> liveCount = name -> "a".equals(name) ? 1 : 0;
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for (int i = 0; i < 5; i++) {
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assertEquals("b", policy.select(ctx(candidates, liveCount)).profile());
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}
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}
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@Test
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void weightedThrowsWhenAllAtMaxLoad() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 1.0f, 1),
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PlacementCandidate.profile("b", 1.0f, 1));
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Function<String, Integer> liveCount = name -> 1;
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PlacementException e = assertThrows(PlacementException.class,
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() -> policy.select(ctx(candidates, liveCount)));
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assertTrue(e.getMessage().contains("maxLoad"), e.getMessage());
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}
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@Test
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void weightedThrowsWhenAllUnreachable() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a"),
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PlacementCandidate.profile("b"));
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PlacementException e = assertThrows(PlacementException.class,
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() -> policy.select(ctx(candidates, noSessions(), Set.of("a", "b"))));
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assertTrue(e.getMessage().contains("unreachable"), e.getMessage());
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}
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@Test
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void mixedExclusionMessageNamesBothReasons() {
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PlacementPolicy policy = PlacementPolicies.weighted();
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List<PlacementCandidate> candidates = List.of(
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PlacementCandidate.profile("a", 1.0f, 1),
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PlacementCandidate.profile("b", 1.0f, null));
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Function<String, Integer> liveCount = name -> "a".equals(name) ? 1 : 0;
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Set<String> unreachable = new HashSet<>();
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unreachable.add("b");
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PlacementException e = assertThrows(PlacementException.class,
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() -> policy.select(ctx(candidates, liveCount, unreachable)));
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assertTrue(e.getMessage().contains("1 at maxLoad"), e.getMessage());
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assertTrue(e.getMessage().contains("1 unreachable"), e.getMessage());
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}
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@Test
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void unknownPolicyNameThrows() {
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assertThrows(IllegalArgumentException.class, () -> PlacementPolicies.fromName("random"));
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}
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}
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