Fix bug of service instance refetching when repeating health check is activated

Fixes gh-899

Author: rchigvintsev

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/HealthCheckServiceInstanceListSupplier.java

@@ -68,9 +68,9 @@ public HealthCheckServiceInstanceListSupplier(ServiceInstanceListSupplier delega
 				.onlyIf(repeatContext -> this.healthCheck.getRefetchInstances())
 				.fixedBackoff(healthCheck.getRefetchInstancesInterval());
 		Flux<List<ServiceInstance>> aliveInstancesFlux = Flux.defer(delegate)
+				.repeatWhen(aliveInstancesReplayRepeat)
 				.switchMap(serviceInstances -> healthCheckFlux(serviceInstances)
-						.map(alive -> Collections.unmodifiableList(new ArrayList<>(alive))))
-				.repeatWhen(aliveInstancesReplayRepeat);
+						.map(alive -> Collections.unmodifiableList(new ArrayList<>(alive))));
 		aliveInstancesReplay = aliveInstancesFlux.delaySubscription(healthCheck.getInitialDelay()).replay(1)
 				.refCount(1);
 	}

spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/core/HealthCheckServiceInstanceListSupplierTests.java

@@ -21,6 +21,7 @@
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BiFunction;
 
 import org.assertj.core.api.Assertions;
 import org.assertj.core.util.Lists;
@@ -440,6 +441,34 @@ protected Mono<Boolean> isAlive(ServiceInstance serviceInstance) {
 				.thenCancel().verify(VERIFY_TIMEOUT);
 	}
 
+	@Test
+	void shouldRefetchInstancesWithRepeatingHealthCheck() {
+		healthCheck.setInitialDelay(Duration.ofSeconds(1));
+		healthCheck.setRepeatHealthCheck(true);
+		healthCheck.setRefetchInstancesInterval(Duration.ofSeconds(1));
+		healthCheck.setRefetchInstances(true);
+		ServiceInstance serviceInstance1 = new DefaultServiceInstance("ignored-service-1", SERVICE_ID, "127.0.0.1",
+				port, false);
+		ServiceInstance serviceInstance2 = new DefaultServiceInstance("ignored-service-2", SERVICE_ID, "127.0.0.2",
+				port, false);
+
+		StepVerifier.withVirtualTime(() -> {
+			ServiceInstanceListSupplier delegate = mock(ServiceInstanceListSupplier.class);
+			when(delegate.get()).thenReturn(Flux.just(Collections.singletonList(serviceInstance1)))
+					.thenReturn(Flux.just(Collections.singletonList(serviceInstance2)));
+			BiFunction<ServiceInstance, String, Mono<Boolean>> healthCheckFunc = healthCheckFunction(webClient);
+			listSupplier = new HealthCheckServiceInstanceListSupplier(delegate, healthCheck, healthCheckFunc) {
+				@Override
+				protected Mono<Boolean> isAlive(ServiceInstance serviceInstance) {
+					return Mono.just(true);
+				}
+			};
+			return listSupplier.get();
+		}).expectSubscription().expectNoEvent(healthCheck.getInitialDelay()).expectNext(Lists.list(serviceInstance1))
+				.thenAwait(healthCheck.getRefetchInstancesInterval()).expectNext(Lists.list(serviceInstance2))
+				.thenCancel().verify(VERIFY_TIMEOUT);
+	}
+
 	@Test
 	void shouldCacheResultIfAfterPropertiesSetInvoked() {
 		healthCheck.setInitialDelay(Duration.ofSeconds(1));