Refactor eager-load PR. Add docs.

docs/src/main/asciidoc/_configprops.adoc

@@ -31,6 +31,7 @@
 |spring.cloud.loadbalancer.cache.ttl | `+++35s+++` | Time To Live - time counted from writing of the record, after which cache entries are expired, expressed as a {@link Duration}. The property {@link String} has to be in keeping with the appropriate syntax as specified in Spring Boot <code>StringToDurationConverter</code>. @see <a href= "https://github.com/spring-projects/spring-boot/blob/master/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/convert/StringToDurationConverter.java">StringToDurationConverter.java</a>
 |spring.cloud.loadbalancer.clients |  | 
 |spring.cloud.loadbalancer.configurations | `+++default+++` | Enables a predefined LoadBalancer configuration.
+|spring.cloud.loadbalancer.eager-load.clients |  | Names of the clients.
 |spring.cloud.loadbalancer.enabled | `+++true+++` | Enables Spring Cloud LoadBalancer.
 |spring.cloud.loadbalancer.health-check.initial-delay | `+++0+++` | Initial delay value for the HealthCheck scheduler.
 |spring.cloud.loadbalancer.health-check.interval | `+++25s+++` | Interval for rerunning the HealthCheck scheduler.
@@ -59,8 +60,6 @@
 |spring.cloud.loadbalancer.sticky-session.instance-id-cookie-name | `+++sc-lb-instance-id+++` | The name of the cookie holding the preferred instance id.
 |spring.cloud.loadbalancer.x-forwarded.enabled | `+++false+++` | To Enable X-Forwarded Headers.
 |spring.cloud.loadbalancer.zone |  | Spring Cloud LoadBalancer zone.
-|spring.cloud.loadbalancer.eager-load.enabled|  | Enables eager load of client context.
-|spring.cloud.loadbalancer.eager-load.clients | |
 |spring.cloud.refresh.additional-property-sources-to-retain |  | Additional property sources to retain during a refresh. Typically only system property sources are retained. This property allows property sources, such as property sources created by EnvironmentPostProcessors to be retained as well.
 |spring.cloud.refresh.enabled | `+++true+++` | Enables autoconfiguration for the refresh scope and associated features.
 |spring.cloud.refresh.extra-refreshable | `+++true+++` | Additional class names for beans to post process into refresh scope.

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

@@ -853,6 +853,12 @@ that retrieves available instances from Service Discovery using a <<discovery-cl
 
 TIP: It is possible to disable Spring Cloud LoadBalancer by setting the value of `spring.cloud.loadbalancer.enabled` to `false`.
 
+=== Eager loading of LoadBalancer contexts
+
+Spring Cloud LoadBalancer creates a separate Spring child context for each service id. By default, these contexts are initialised lazily, whenever the first request for a service id is being load-balanced.
+
+You can choose to load those contexts eagerly. In order to do that, specify the service ids for which you want to do eager load using the `spring.cloud-loadbalancer.eager-load.clients` property.
+
 === Switching between the load-balancing algorithms
 
 The `ReactiveLoadBalancer` implementation that is used by default is `RoundRobinLoadBalancer`. To switch to a different implementation, either for selected services or all of them, you can use the <<custom-loadbalancer-configuration, custom LoadBalancer configurations mechanism>>.

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/LoadBalancerEagerLoadProperties.java

@@ -25,7 +25,7 @@ import org.springframework.boot.context.properties.ConfigurationProperties;
  * @author Andrii Bohutskyi
  */
 @ConfigurationProperties("spring.cloud.loadbalancer.eager-load")
-public class LoadbalancerEagerLoadProperties {
+public class LoadBalancerEagerLoadProperties {
 
 	private List<String> clients = new ArrayList<>();
 
@@ -36,4 +36,5 @@ public class LoadbalancerEagerLoadProperties {
 	public void setClients(List<String> clients) {
 		this.clients = clients;
 	}
+
 }

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/config/LoadBalancerAutoConfiguration.java

@@ -25,7 +25,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerClientsProperties;
-import org.springframework.cloud.client.loadbalancer.LoadbalancerEagerLoadProperties;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerEagerLoadProperties;
 import org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerBeanPostProcessorAutoConfiguration;
 import org.springframework.cloud.client.loadbalancer.reactive.ReactorLoadBalancerClientAutoConfiguration;
 import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClientSpecification;
@@ -42,7 +42,7 @@ import org.springframework.core.env.Environment;
  */
 @Configuration(proxyBeanMethods = false)
 @LoadBalancerClients
-@EnableConfigurationProperties(LoadBalancerClientsProperties.class)
+@EnableConfigurationProperties({ LoadBalancerClientsProperties.class, LoadBalancerEagerLoadProperties.class })
 @AutoConfigureBefore({ ReactorLoadBalancerClientAutoConfiguration.class,
 		LoadBalancerBeanPostProcessorAutoConfiguration.class })
 @ConditionalOnProperty(value = "spring.cloud.loadbalancer.enabled", havingValue = "true", matchIfMissing = true)
@@ -69,9 +69,9 @@ public class LoadBalancerAutoConfiguration {
 	}
 
 	@Bean
-	@ConditionalOnProperty(value = "spring.cloud.loadbalancer.eager-load.enabled", havingValue = "true")
 	public LoadBalancerEagerContextInitializer loadBalancerEagerContextInitializer(
-			LoadBalancerClientFactory clientFactory, LoadbalancerEagerLoadProperties properties) {
+			LoadBalancerClientFactory clientFactory, LoadBalancerEagerLoadProperties properties) {
 		return new LoadBalancerEagerContextInitializer(clientFactory, properties.getClients());
 	}
+
 }

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/support/LoadBalancerEagerContextInitializer.java

@@ -16,11 +16,11 @@
 
 package org.springframework.cloud.loadbalancer.support;
 
+import java.util.List;
+
 import org.springframework.boot.context.event.ApplicationReadyEvent;
 import org.springframework.context.ApplicationListener;
 
-import java.util.List;
-
 /**
  * @author Andrii Bohutskyi
  */
@@ -37,11 +37,7 @@ public class LoadBalancerEagerContextInitializer implements ApplicationListener<
 
 	@Override
 	public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) {
-		warnUpFunction();
-	}
-
-	private void warnUpFunction() {
-		this.serviceNames.forEach(factory::getInstance);
+		serviceNames.forEach(factory::getInstance);
 	}
 
 }

spring-cloud-loadbalancer/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -34,11 +34,6 @@
 			"description": "Enables Spring Cloud LoadBalancer.",
 			"type": "java.lang.Boolean"
 		},
-		{
-			"name": "spring.cloud.loadbalancer.eager-load.enabled",
-			"description": "Enables eager load of clients context.",
-			"type": "java.lang.Boolean"
-		},
 		{
 			"name": "spring.cloud.loadbalancer.eager-load.clients",
 			"description": "Names of the clients.",

spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/support/LoadBalancerEagerContextInitializerTest.java

@@ -16,29 +16,25 @@
 
 package org.springframework.cloud.loadbalancer.support;
 
+import java.util.Collections;
+import java.util.concurrent.atomic.AtomicInteger;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;
 import org.springframework.cloud.loadbalancer.config.LoadBalancerAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.test.context.junit.jupiter.SpringExtension;
-
-import java.util.Collections;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * @author Andrii Bohutskyi
  */
-@ExtendWith(SpringExtension.class)
-@SpringBootTest(classes = {
-		LoadBalancerAutoConfiguration.class,
-		LoadBalancerEagerContextInitializerTest.SomeTestConfig.class
-})
+@SpringBootTest(
+		classes = { LoadBalancerAutoConfiguration.class, LoadBalancerEagerContextInitializerTest.SomeTestConfig.class })
 class LoadBalancerEagerContextInitializerTest {
 
 	private static final String LOAD_BALANCER = "testLoadBalancer";
@@ -58,7 +54,7 @@ class LoadBalancerEagerContextInitializerTest {
 	static class SomeTestConfig {
 
 		@Bean
-		public LoadBalancerEagerContextInitializer loadBalancerEagerContextInitializer(
+		public LoadBalancerEagerContextInitializer testLoadBalancerEagerContextInitializer(
 				LoadBalancerClientFactory factory) {
 			return new LoadBalancerEagerContextInitializer(factory, Collections.singletonList(LOAD_BALANCER));
 		}
@@ -78,12 +74,14 @@ class LoadBalancerEagerContextInitializerTest {
 
 		private static final AtomicInteger COUNT = new AtomicInteger();
 
-		public LoadBalancerCounter() {
+		LoadBalancerCounter() {
 			COUNT.incrementAndGet();
 		}
 
 		public static int getCount() {
 			return COUNT.get();
 		}
+
 	}
+
 }