Add predefined ServiceInstanceListSupplier configurations.

docs/src/main/asciidoc/spring-cloud-commons.adoc

@@ -970,6 +970,8 @@ public class CustomLoadBalancerConfiguration {
 
 TIP:: In order to make working on your own LoadBalancer configuration easier, we have added some utility methods in `ServiceInstanceListSuppliers` class.
 
+TIP:: You can also use our alternative predefined configurations in place of the default ones by setting the value of `spring.cloud.loadbalancer.configurations` property to `zone-preference` to use `ZonePreferenceServiceInstanceListSupplier` with caching or to `health-check` to use `HealthCheckServiceInstanceListSupplier` with caching.
+
 [[spring-cloud-loadbalancer-starter]]
 === Spring Cloud LoadBalancer Starter
 

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfiguration.java

@@ -19,6 +19,7 @@
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.cloud.client.ConditionalOnBlockingDiscoveryEnabled;
 import org.springframework.cloud.client.ConditionalOnDiscoveryEnabled;
 import org.springframework.cloud.client.ConditionalOnReactiveDiscoveryEnabled;
@@ -70,12 +71,36 @@ public static class ReactiveSupportConfiguration {
 		@Bean
 		@ConditionalOnBean(ReactiveDiscoveryClient.class)
 		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "default", matchIfMissing = true)
 		public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
 				ConfigurableApplicationContext context) {
 			return ServiceInstanceListSuppliers.builder().withDiscoveryClient()
 					.withCaching().build(context);
 		}
 
+		@Bean
+		@ConditionalOnBean(ReactiveDiscoveryClient.class)
+		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "zone-preference")
+		public ServiceInstanceListSupplier zonePreferenceDiscoveryClientServiceInstanceListSupplier(
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withDiscoveryClient()
+					.withZonePreference().withCaching().build(context);
+		}
+
+		@Bean
+		@ConditionalOnBean(ReactiveDiscoveryClient.class)
+		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "health-check")
+		public ServiceInstanceListSupplier healthCheckDiscoveryClientServiceInstanceListSupplier(
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withDiscoveryClient()
+					.withHealthChecks().withCaching().build(context);
+		}
+
 		@Bean
 		@ConditionalOnBean(ReactiveDiscoveryClient.class)
 		@ConditionalOnMissingBean
@@ -103,12 +128,36 @@ public static class BlockingSupportConfiguration {
 		@Bean
 		@ConditionalOnBean(DiscoveryClient.class)
 		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "default", matchIfMissing = true)
 		public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
 				ConfigurableApplicationContext context) {
 			return ServiceInstanceListSuppliers.builder().withBlockingDiscoveryClient()
 					.withCaching().build(context);
 		}
 
+		@Bean
+		@ConditionalOnBean(DiscoveryClient.class)
+		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "zone-preference")
+		public ServiceInstanceListSupplier zonePreferenceDiscoveryClientServiceInstanceListSupplier(
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withBlockingDiscoveryClient()
+					.withZonePreference().withCaching().build(context);
+		}
+
+		@Bean
+		@ConditionalOnBean(DiscoveryClient.class)
+		@ConditionalOnMissingBean
+		@ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations",
+				havingValue = "health-check")
+		public ServiceInstanceListSupplier healthCheckDiscoveryClientServiceInstanceListSupplier(
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withBlockingDiscoveryClient()
+					.withHealthChecks().withCaching().build(context);
+		}
+
 		@Bean
 		@ConditionalOnBean(DiscoveryClient.class)
 		@ConditionalOnMissingBean

spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfigurationTests.java

@@ -0,0 +1,176 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.loadbalancer.annotation;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.cloud.client.discovery.composite.CompositeDiscoveryClientAutoConfiguration;
+import org.springframework.cloud.client.discovery.composite.reactive.ReactiveCompositeDiscoveryClientAutoConfiguration;
+import org.springframework.cloud.client.loadbalancer.LoadBalanced;
+import org.springframework.cloud.loadbalancer.config.LoadBalancerAutoConfiguration;
+import org.springframework.cloud.loadbalancer.config.LoadBalancerCacheAutoConfiguration;
+import org.springframework.cloud.loadbalancer.core.CachingServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.CachingServiceInstanceSupplier;
+import org.springframework.cloud.loadbalancer.core.DelegatingServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.DiscoveryClientServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.HealthCheckServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.ServiceInstanceSupplier;
+import org.springframework.cloud.loadbalancer.core.ZonePreferenceServiceInstanceListSupplier;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+/**
+ * Tests for {@link LoadBalancerClientConfiguration}.
+ *
+ * @author Olga Maciaszek-Sharma
+ */
+class LoadBalancerClientConfigurationTests {
+
+	ApplicationContextRunner reactiveDiscoveryClientRunner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(
+					ReactiveCompositeDiscoveryClientAutoConfiguration.class,
+					LoadBalancerCacheAutoConfiguration.class,
+					LoadBalancerAutoConfiguration.class,
+					LoadBalancerClientConfiguration.class));
+
+	ApplicationContextRunner blockingDiscoveryClientRunner = new ApplicationContextRunner()
+			.withConfiguration(
+					AutoConfigurations.of(CompositeDiscoveryClientAutoConfiguration.class,
+							LoadBalancerCacheAutoConfiguration.class,
+							LoadBalancerAutoConfiguration.class,
+							LoadBalancerClientConfiguration.class));
+
+	@Test
+	void shouldInstantiateDefaultServiceInstanceListSupplierWhenConfigurationsPropertyNotSet() {
+		reactiveDiscoveryClientRunner.run(context -> {
+			ServiceInstanceListSupplier supplier = context
+					.getBean(ServiceInstanceListSupplier.class);
+			then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+			then(((DelegatingServiceInstanceListSupplier) supplier).getDelegate())
+					.isInstanceOf(DiscoveryClientServiceInstanceListSupplier.class);
+		});
+	}
+
+	@Test
+	void shouldInstantiateDefaultServiceInstanceListSupplier() {
+		reactiveDiscoveryClientRunner
+				.withPropertyValues("spring.cloud.loadbalancer.configurations=default")
+				.run(context -> {
+					ServiceInstanceListSupplier supplier = context
+							.getBean(ServiceInstanceListSupplier.class);
+					then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+					then(((DelegatingServiceInstanceListSupplier) supplier).getDelegate())
+							.isInstanceOf(
+									DiscoveryClientServiceInstanceListSupplier.class);
+				});
+	}
+
+	@Test
+	void shouldInstantiateZonePreferenceServiceInstanceListSupplier() {
+		reactiveDiscoveryClientRunner
+				.withPropertyValues(
+						"spring.cloud.loadbalancer.configurations=zone-preference")
+				.run(context -> {
+					ServiceInstanceListSupplier supplier = context
+							.getBean(ServiceInstanceListSupplier.class);
+					then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+					ServiceInstanceListSupplier delegate = ((DelegatingServiceInstanceListSupplier) supplier)
+							.getDelegate();
+					then(delegate).isInstanceOf(
+							ZonePreferenceServiceInstanceListSupplier.class);
+					ServiceInstanceListSupplier secondDelegate = ((DelegatingServiceInstanceListSupplier) delegate)
+							.getDelegate();
+					then(secondDelegate).isInstanceOf(
+							DiscoveryClientServiceInstanceListSupplier.class);
+				});
+	}
+
+	@Test
+	void shouldInstantiateHealthCheckServiceInstanceListSupplier() {
+		reactiveDiscoveryClientRunner.withUserConfiguration(TestConfig.class)
+				.withPropertyValues(
+						"spring.cloud.loadbalancer.configurations=health-check")
+				.run(context -> {
+					ServiceInstanceListSupplier supplier = context
+							.getBean(ServiceInstanceListSupplier.class);
+					then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+					ServiceInstanceListSupplier delegate = ((DelegatingServiceInstanceListSupplier) supplier)
+							.getDelegate();
+					then(delegate)
+							.isInstanceOf(HealthCheckServiceInstanceListSupplier.class);
+					ServiceInstanceListSupplier secondDelegate = ((DelegatingServiceInstanceListSupplier) delegate)
+							.getDelegate();
+					then(secondDelegate).isInstanceOf(
+							DiscoveryClientServiceInstanceListSupplier.class);
+				});
+	}
+
+	@Test
+	void shouldInstantiateDefaultBlockingServiceInstanceListSupplierWhenConfigurationsPropertyNotSet() {
+		blockingDiscoveryClientRunner.run(context -> {
+			ServiceInstanceListSupplier supplier = context
+					.getBean(ServiceInstanceListSupplier.class);
+			then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+			then(((DelegatingServiceInstanceListSupplier) supplier).getDelegate())
+					.isInstanceOf(DiscoveryClientServiceInstanceListSupplier.class);
+		});
+	}
+
+	@Test
+	void shouldInstantiateDefaultBlockingServiceInstanceListSupplier() {
+		blockingDiscoveryClientRunner
+				.withPropertyValues("spring.cloud.loadbalancer.configurations=default")
+				.run(context -> {
+					ServiceInstanceListSupplier supplier = context
+							.getBean(ServiceInstanceListSupplier.class);
+					then(supplier).isInstanceOf(CachingServiceInstanceListSupplier.class);
+					then(((DelegatingServiceInstanceListSupplier) supplier).getDelegate())
+							.isInstanceOf(
+									DiscoveryClientServiceInstanceListSupplier.class);
+				});
+	}
+
+	@Test
+	void shouldInstantiateServiceInstanceSupplierRegardlessOfConfigurationProperty() {
+		reactiveDiscoveryClientRunner
+				.withPropertyValues(
+						"spring.cloud.loadbalancer.configurations=zone-preference")
+				.run(context -> {
+					ServiceInstanceSupplier supplier = context
+							.getBean(ServiceInstanceSupplier.class);
+					then(supplier).isInstanceOf(CachingServiceInstanceSupplier.class);
+				});
+	}
+
+	@Configuration
+	protected static class TestConfig {
+
+		@Bean
+		@LoadBalanced
+		WebClient.Builder webClientBuilder() {
+			return WebClient.builder();
+		}
+
+	}
+
+}