Lb configuration builders

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

@@ -917,22 +917,14 @@ public class CustomLoadBalancerConfiguration {
 
 	@Bean
 	public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
-			ReactiveDiscoveryClient discoveryClient, Environment environment,
-			LoadBalancerZoneConfig zoneConfig,
-			ApplicationContext context) {
-		DiscoveryClientServiceInstanceListSupplier firstDelegate = new DiscoveryClientServiceInstanceListSupplier(
-				discoveryClient, environment);
-		ZonePreferenceServiceInstanceListSupplier delegate = new ZonePreferenceServiceInstanceListSupplier(firstDelegate,
-				zoneConfig);
-		ObjectProvider<LoadBalancerCacheManager> cacheManagerProvider = context
-				.getBeanProvider(LoadBalancerCacheManager.class);
-		if (cacheManagerProvider.getIfAvailable() != null) {
-			return new CachingServiceInstanceListSupplier(delegate,
-					cacheManagerProvider.getIfAvailable());
-		}
-		return delegate;
-	}
+			ConfigurableApplicationContext context) {
+		return ServiceInstanceListSuppliers.builder()
+					.withDiscoveryClient()
+					.withZonePreference()
+					.withCaching()
+					.build(context);
 	}
+}
 ----
 
 === Instance Health-Check for LoadBalancer
@@ -966,25 +958,18 @@ public class CustomLoadBalancerConfiguration {
 
 	@Bean
 	public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
-			ReactiveDiscoveryClient discoveryClient, Environment environment,
-			LoadBalancerProperties loadBalancerProperties,
-			ApplicationContext context,
-			InstanceHealthChecker healthChecker) {
-		DiscoveryClientServiceInstanceListSupplier firstDelegate = new DiscoveryClientServiceInstanceListSupplier(
-				discoveryClient, environment);
-		HealthCheckServiceInstanceListSupplier delegate = new HealthCheckServiceInstanceListSupplier(firstDelegate,
-				loadBalancerProperties, healthChecker);
-		ObjectProvider<LoadBalancerCacheManager> cacheManagerProvider = context
-				.getBeanProvider(LoadBalancerCacheManager.class);
-		if (cacheManagerProvider.getIfAvailable() != null) {
-			return new CachingServiceInstanceListSupplier(delegate,
-					cacheManagerProvider.getIfAvailable());
-		}
-		return delegate;
-	}
+			ConfigurableApplicationContext context) {
+		return ServiceInstanceListSuppliers.builder()
+					.withDiscoveryClient()
+					.withHealthChecks()
+					.withCaching()
+					.build(context);
+	    }
 	}
 ----
 
+TIP:: In order to make working on your own LoadBalancer configuration easier, we have added some utility methods in `ServiceInstanceListSuppliers` class.
+
 [[spring-cloud-loadbalancer-starter]]
 === Spring Cloud LoadBalancer Starter
 

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

@@ -26,16 +26,16 @@
 import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.cloud.client.discovery.ReactiveDiscoveryClient;
 import org.springframework.cloud.loadbalancer.cache.LoadBalancerCacheManager;
-import org.springframework.cloud.loadbalancer.core.CachingServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.CachingServiceInstanceSupplier;
-import org.springframework.cloud.loadbalancer.core.DiscoveryClientServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.DiscoveryClientServiceInstanceSupplier;
 import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSuppliers;
 import org.springframework.cloud.loadbalancer.core.ServiceInstanceSupplier;
 import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.Order;
@@ -71,17 +71,9 @@ public static class ReactiveSupportConfiguration {
 		@ConditionalOnBean(ReactiveDiscoveryClient.class)
 		@ConditionalOnMissingBean
 		public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
-				ReactiveDiscoveryClient discoveryClient, Environment env,
-				ApplicationContext context) {
-			DiscoveryClientServiceInstanceListSupplier delegate = new DiscoveryClientServiceInstanceListSupplier(
-					discoveryClient, env);
-			ObjectProvider<LoadBalancerCacheManager> cacheManagerProvider = context
-					.getBeanProvider(LoadBalancerCacheManager.class);
-			if (cacheManagerProvider.getIfAvailable() != null) {
-				return new CachingServiceInstanceListSupplier(delegate,
-						cacheManagerProvider.getIfAvailable());
-			}
-			return delegate;
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withDiscoveryClient()
+					.withCaching().build(context);
 		}
 
 		@Bean
@@ -112,17 +104,9 @@ public static class BlockingSupportConfiguration {
 		@ConditionalOnBean(DiscoveryClient.class)
 		@ConditionalOnMissingBean
 		public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
-				DiscoveryClient discoveryClient, Environment env,
-				ApplicationContext context) {
-			DiscoveryClientServiceInstanceListSupplier delegate = new DiscoveryClientServiceInstanceListSupplier(
-					discoveryClient, env);
-			ObjectProvider<LoadBalancerCacheManager> cacheManagerProvider = context
-					.getBeanProvider(LoadBalancerCacheManager.class);
-			if (cacheManagerProvider.getIfAvailable() != null) {
-				return new CachingServiceInstanceListSupplier(delegate,
-						cacheManagerProvider.getIfAvailable());
-			}
-			return delegate;
+				ConfigurableApplicationContext context) {
+			return ServiceInstanceListSuppliers.builder().withBlockingDiscoveryClient()
+					.withCaching().build(context);
 		}
 
 		@Bean

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

@@ -37,7 +37,8 @@
  * @author Olga Maciaszek-Sharma
  * @since 2.2.0
  */
-public class CachingServiceInstanceListSupplier implements ServiceInstanceListSupplier {
+public class CachingServiceInstanceListSupplier
+		extends DelegatingServiceInstanceListSupplier {
 
 	private static final Log log = LogFactory
 			.getLog(CachingServiceInstanceListSupplier.class);
@@ -48,14 +49,12 @@ public class CachingServiceInstanceListSupplier implements ServiceInstanceListSu
 	public static final String SERVICE_INSTANCE_CACHE_NAME = CachingServiceInstanceListSupplier.class
 			.getSimpleName() + "Cache";
 
-	private final ServiceInstanceListSupplier delegate;
-
 	private final Flux<List<ServiceInstance>> serviceInstances;
 
 	@SuppressWarnings("unchecked")
 	public CachingServiceInstanceListSupplier(ServiceInstanceListSupplier delegate,
 			CacheManager cacheManager) {
-		this.delegate = delegate;
+		super(delegate);
 		this.serviceInstances = CacheFlux.lookup(key -> {
 			// TODO: configurable cache name
 			Cache cache = cacheManager.getCache(SERVICE_INSTANCE_CACHE_NAME);
@@ -70,7 +69,7 @@ public CachingServiceInstanceListSupplier(ServiceInstanceListSupplier delegate,
 				return Mono.empty();
 			}
 			return Flux.just(list).materialize().collectList();
-		}, delegate.getServiceId()).onCacheMissResume(this.delegate)
+		}, delegate.getServiceId()).onCacheMissResume(delegate)
 				.andWriteWith((key, signals) -> Flux.fromIterable(signals).dematerialize()
 						.doOnNext(instances -> {
 							Cache cache = cacheManager
@@ -87,11 +86,6 @@ public CachingServiceInstanceListSupplier(ServiceInstanceListSupplier delegate,
 						}).then());
 	}
 
-	@Override
-	public String getServiceId() {
-		return delegate.getServiceId();
-	}
-
 	@Override
 	public Flux<List<ServiceInstance>> get() {
 		return serviceInstances;

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

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012-2019 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.core;
+
+import org.springframework.util.Assert;
+
+/**
+ * Represents a {@link ServiceInstanceListSupplier} that uses a delegate
+ * {@link ServiceInstanceListSupplier} instance underneath.
+ *
+ * @author Spencer Gibb
+ */
+public abstract class DelegatingServiceInstanceListSupplier
+		implements ServiceInstanceListSupplier {
+
+	private final ServiceInstanceListSupplier delegate;
+
+	public DelegatingServiceInstanceListSupplier(ServiceInstanceListSupplier delegate) {
+		Assert.notNull(delegate, "delegate may not be null");
+		this.delegate = delegate;
+	}
+
+	public ServiceInstanceListSupplier getDelegate() {
+		return this.delegate;
+	}
+
+	@Override
+	public String getServiceId() {
+		return this.delegate.getServiceId();
+	}
+
+}

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

@@ -45,13 +45,12 @@
  * @since 2.2.0
  */
 public class HealthCheckServiceInstanceListSupplier
-		implements ServiceInstanceListSupplier, InitializingBean, DisposableBean {
+		extends DelegatingServiceInstanceListSupplier
+		implements InitializingBean, DisposableBean {
 
 	private static final Log LOG = LogFactory
 			.getLog(HealthCheckServiceInstanceListSupplier.class);
 
-	private final ServiceInstanceListSupplier delegate;
-
 	private final LoadBalancerProperties.HealthCheck healthCheck;
 
 	private final WebClient webClient;
@@ -64,7 +63,7 @@ public class HealthCheckServiceInstanceListSupplier
 
 	public HealthCheckServiceInstanceListSupplier(ServiceInstanceListSupplier delegate,
 			LoadBalancerProperties.HealthCheck healthCheck, WebClient webClient) {
-		this.delegate = delegate;
+		super(delegate);
 		this.healthCheck = healthCheck;
 		defaultHealthCheckPath = healthCheck.getPath().getOrDefault("default",
 				"/actuator/health");
@@ -121,11 +120,6 @@ protected Flux<List<ServiceInstance>> healthCheckFlux(
 		}).repeatWhen(restart -> restart.delayElements(healthCheck.getInterval()));
 	}
 
-	@Override
-	public String getServiceId() {
-		return delegate.getServiceId();
-	}
-
 	@Override
 	public Flux<List<ServiceInstance>> get() {
 		return aliveInstancesReplay;