feat(lb): deterministic subsetting algorithm to limit the number of i…

…nstances
spring-cloud · Oct 28, 2023 · 48bbf98 · 48bbf98
1 parent 22e212a
commit 48bbf98
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Showing 2 changed files with 14 additions and 1 deletion.
diff --git a/...n/java/org/springframework/cloud/loadbalancer/core/SubsetServiceInstanceListSupplier.java b/...n/java/org/springframework/cloud/loadbalancer/core/SubsetServiceInstanceListSupplier.java
@@ -58,7 +58,7 @@ public SubsetServiceInstanceListSupplier(ServiceInstanceListSupplier delegate, S
 	@Override
 	public Flux<List<ServiceInstance>> get() {
 		return delegate.get().map(instances -> {
-			if (instances.isEmpty()) {
+			if (instances.size() <= subsetSize) {
 				return instances;
 			}
 

diff --git a/...va/org/springframework/cloud/loadbalancer/core/SubsetServiceInstanceListSupplierTest.java b/...va/org/springframework/cloud/loadbalancer/core/SubsetServiceInstanceListSupplierTest.java
@@ -74,6 +74,19 @@ void shouldReturnSublistWithGivenSubsetSize() {
 		assertThat(serviceInstances).hasSize(5);
 	}
 
+	@Test
+	void shouldReturnRawWhenLessThanSubsetSize() {
+		List<ServiceInstance> instances = IntStream.range(0, 101)
+				.mapToObj(i -> new DefaultServiceInstance(Integer.toString(i), "test", "host" + i, 8080, false, null))
+				.collect(Collectors.toList());
+
+		when(delegate.get()).thenReturn(Flux.just(instances));
+		SubsetServiceInstanceListSupplier supplier = new SubsetServiceInstanceListSupplier(delegate, 1000);
+
+		List<ServiceInstance> serviceInstances = Objects.requireNonNull(supplier.get().blockFirst());
+		assertThat(serviceInstances).hasSize(101);
+	}
+
 	@Test
 	void shouldReturnSameSublistForSameInstanceId() {
 		List<ServiceInstance> instances = IntStream.range(0, 101)