Optimize instance selection performance (#1363)

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -29,11 +29,13 @@
 import org.springframework.cloud.client.loadbalancer.EmptyResponse;
 import org.springframework.cloud.client.loadbalancer.Request;
 import org.springframework.cloud.client.loadbalancer.Response;
+import org.springframework.util.function.SingletonSupplier;
 
 /**
  * A random-based implementation of {@link ReactorServiceInstanceLoadBalancer}.
  *
  * @author Olga Maciaszek-Sharma
+ * @author Nan Chiu
  * @since 2.2.7
  */
 public class RandomLoadBalancer implements ReactorServiceInstanceLoadBalancer {
@@ -42,7 +44,7 @@ public class RandomLoadBalancer implements ReactorServiceInstanceLoadBalancer {
 
 	private final String serviceId;
 
-	private ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
+	private final SingletonSupplier<ServiceInstanceListSupplier> serviceInstanceListSingletonSupplier;
 
 	/**
 	 * @param serviceInstanceListSupplierProvider a provider of
@@ -52,14 +54,15 @@ public class RandomLoadBalancer implements ReactorServiceInstanceLoadBalancer {
 	public RandomLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
 			String serviceId) {
 		this.serviceId = serviceId;
-		this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
+		this.serviceInstanceListSingletonSupplier = SingletonSupplier.of(
+				() -> serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new)
+		);
 	}
 
 	@SuppressWarnings("rawtypes")
 	@Override
 	public Mono<Response<ServiceInstance>> choose(Request request) {
-		ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
-			.getIfAvailable(NoopServiceInstanceListSupplier::new);
+		ServiceInstanceListSupplier supplier = serviceInstanceListSingletonSupplier.obtain();
 		return supplier.get(request)
 			.next()
 			.map(serviceInstances -> processInstanceResponse(supplier, serviceInstances));

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -30,13 +30,15 @@
 import org.springframework.cloud.client.loadbalancer.EmptyResponse;
 import org.springframework.cloud.client.loadbalancer.Request;
 import org.springframework.cloud.client.loadbalancer.Response;
+import org.springframework.util.function.SingletonSupplier;
 
 /**
  * A Round-Robin-based implementation of {@link ReactorServiceInstanceLoadBalancer}.
  *
  * @author Spencer Gibb
  * @author Olga Maciaszek-Sharma
  * @author Zhuozhi JI
+ * @author Nan Chiu
  */
 public class RoundRobinLoadBalancer implements ReactorServiceInstanceLoadBalancer {
 
@@ -46,7 +48,7 @@ public class RoundRobinLoadBalancer implements ReactorServiceInstanceLoadBalance
 
 	final String serviceId;
 
-	ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
+	private final SingletonSupplier<ServiceInstanceListSupplier> serviceInstanceListSingletonSupplier;
 
 	/**
 	 * @param serviceInstanceListSupplierProvider a provider of
@@ -67,7 +69,9 @@ public RoundRobinLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> servic
 	public RoundRobinLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
 			String serviceId, int seedPosition) {
 		this.serviceId = serviceId;
-		this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
+		this.serviceInstanceListSingletonSupplier = SingletonSupplier.of(
+				() -> serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new)
+		);
 		this.position = new AtomicInteger(seedPosition);
 	}
 
@@ -77,8 +81,7 @@ public RoundRobinLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> servic
 	// https://github.com/Netflix/ocelli/blob/master/ocelli-core/
 	// src/main/java/netflix/ocelli/loadbalancer/RoundRobinLoadBalancer.java
 	public Mono<Response<ServiceInstance>> choose(Request request) {
-		ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
-			.getIfAvailable(NoopServiceInstanceListSupplier::new);
+		ServiceInstanceListSupplier supplier = serviceInstanceListSingletonSupplier.obtain();
 		return supplier.get(request)
 			.next()
 			.map(serviceInstances -> processInstanceResponse(supplier, serviceInstances));