From dca203ce653c3366b9073ad009b7c56fdd50395f Mon Sep 17 00:00:00 2001
From: Haotian Zhang <928016560@qq.com>
Date: Wed, 25 Jun 2025 16:40:20 +0800
Subject: [PATCH] feat:support setting load balancing strategy per service.

---
 .../LoadBalancerClientConfiguration.java      | 33 +++++++++++++++++++
 .../LoadBalancerClientConfigurationTests.java | 22 +++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfiguration.java b/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfiguration.java
index dd8a4fce7..8b2d50bcf 100644
--- a/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfiguration.java
+++ b/spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfiguration.java
@@ -30,6 +30,7 @@
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.cloud.client.discovery.ReactiveDiscoveryClient;
+import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.RetryAwareServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer;
@@ -59,6 +60,7 @@
  * @author BaoLin Zhu
  * @author changjin wei(魏昌进)
  * @author Zhuozhi Ji
+ * @author Haotian Zhang
  */
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnDiscoveryEnabled
@@ -68,6 +70,7 @@ public class LoadBalancerClientConfiguration {
 
 	@Bean
 	@ConditionalOnMissingBean
+	@Conditional(DefaultStrategyCondition.class)
 	public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
 			LoadBalancerClientFactory loadBalancerClientFactory) {
 		String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
@@ -75,6 +78,16 @@ public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(E
 				loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
 	}
 
+	@Bean
+	@ConditionalOnMissingBean
+	@Conditional(RandomStrategyCondition.class)
+	public ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
+			LoadBalancerClientFactory loadBalancerClientFactory) {
+		String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
+		return new RandomLoadBalancer(
+				loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@ConditionalOnReactiveDiscoveryEnabled
 	@Order(REACTIVE_SERVICE_INSTANCE_SUPPLIER_ORDER)
@@ -309,6 +322,26 @@ public ServiceInstanceListSupplier retryAwareDiscoveryClientServiceInstanceListS
 
 	}
 
+	static class DefaultStrategyCondition implements Condition {
+
+		@Override
+		public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+			return LoadBalancerEnvironmentPropertyUtils.equalToForClientOrDefault(context.getEnvironment(),
+					"strategies", "default");
+		}
+
+	}
+
+	static class RandomStrategyCondition implements Condition {
+
+		@Override
+		public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+			return LoadBalancerEnvironmentPropertyUtils.equalToForClientOrDefault(context.getEnvironment(),
+					"strategies", "random");
+		}
+
+	}
+
 	static final class BlockingOnAvoidPreviousInstanceAndRetryEnabledCondition extends AllNestedConditions {
 
 		private BlockingOnAvoidPreviousInstanceAndRetryEnabledCondition() {
diff --git a/spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfigurationTests.java b/spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfigurationTests.java
index f9e4826c3..8aac0bf19 100644
--- a/spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfigurationTests.java
+++ b/spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/annotation/LoadBalancerClientConfigurationTests.java
@@ -35,8 +35,11 @@
 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.RandomLoadBalancer;
+import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.RequestBasedStickySessionServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.RetryAwareServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer;
 import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.WeightedServiceInstanceListSupplier;
 import org.springframework.cloud.loadbalancer.core.ZonePreferenceServiceInstanceListSupplier;
@@ -54,6 +57,7 @@
  *
  * @author Olga Maciaszek-Sharma
  * @author Zhuozhi Ji
+ * @author Haotian Zhang
  */
 class LoadBalancerClientConfigurationTests {
 
@@ -221,6 +225,24 @@ void shouldInstantiateBlockingWeightedServiceInstanceListSupplier() {
 			});
 	}
 
+	@Test
+	void shouldInstantiateRoundRobinLoadBalancer() {
+		blockingDiscoveryClientRunner.withPropertyValues("spring.cloud.loadbalancer.strategies=default")
+				.run(context -> {
+					ReactorLoadBalancer<?> reactorLoadBalancer = context.getBean(ReactorLoadBalancer.class);
+					then(reactorLoadBalancer).isInstanceOf(RoundRobinLoadBalancer.class);
+				});
+	}
+
+	@Test
+	void shouldInstantiateRandomLoadBalancer() {
+		blockingDiscoveryClientRunner.withPropertyValues("spring.cloud.loadbalancer.strategies=random")
+				.run(context -> {
+					ReactorLoadBalancer<?> reactorLoadBalancer = context.getBean(ReactorLoadBalancer.class);
+					then(reactorLoadBalancer).isInstanceOf(RandomLoadBalancer.class);
+				});
+	}
+
 	private static Stream<Arguments> blockingConfigurations() {
 		return Stream.of(Arguments.of(RestTemplateTestConfig.class), Arguments.of(RestClientTestConfig.class),
 				Arguments.of(RestTemplateAndRestClientConfig.class));