Spring Cloud LoadBalancer--指定负载均衡策略--方法/实例

简介

        本文介绍Spring Cloud LoadBalancer如何使用某个指定的负载均衡策略。

        目标：使用Spring Cloud LoadBalance提供的RandomLoadBalancer作为负载均衡策略。其对应的类为：org.springframework.cloud.loadbalancer.core.RandomLoadBalancer。

法1：启动类加@LoadBalancerClients（全局）

第1步：添加配置类（不要加@Configuration）

package com.knife.router4j.example.order.config;
 
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;
 
public class MyLoadBalancerClientConfiguration {
 
  @Bean
  public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
                                           LoadBalancerClientFactory loadBalancerClientFactory) {
    String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    return new RandomLoadBalancer(
        loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
  }
}

第2步：@LoadBalancerClients导入配置

法1：放到启动类上

package com.knife.router4j.example.order;

import com.knife.common.annotation.CommonApplication;
import com.knife.router4j.example.order.config.MyLoadBalancerClientConfiguration;
import org.springframework.boot.SpringApplication;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients("com.knife.**.api")
@LoadBalancerClients(defaultConfiguration = {MyLoadBalancerClientConfiguration.class})
public class OrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }

}

法2：放到@Configuration类上 

package com.knife.router4j.example.order.config;

import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClients;
import org.springframework.context.annotation.Configuration;

@Configuration(proxyBeanMethods = false)
@LoadBalancerClients(defaultConfiguration = MyLoadBalancerConfiguration.class)
public class DefaultLoadBalancerConfiguration {
}

法2：@LoadBalancerClient（局部）

第1步：添加配置类（不要加@Configuration）

package com.knife.router4j.example.order.config;
 
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;
 
public class MyLoadBalancerClientConfiguration {
 
  @Bean
  public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
                                           LoadBalancerClientFactory loadBalancerClientFactory) {
    String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    return new RandomLoadBalancer(
        loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
  }
}

第2步：在启动类上添加@LoadBalancerClient

指定哪个服务（本示例为“storage”）使用新的负载均衡策略：

package com.knife.router4j.example.order;

import com.knife.common.annotation.CommonApplication;
import com.knife.router4j.example.order.config.MyLoadBalancerClientConfiguration;
import org.springframework.boot.SpringApplication;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients("com.knife.**.api")
@LoadBalancerClient(name = "storage", configuration = MyLoadBalancerClientConfiguration.class)
public class OrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }

}

错误的方法

将负载均衡策略注册为bean

        这样是不行的。因为这样会导致environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);返回为null，后边调用feign时会失败。

        官网也说不能直接用@Configuration注册。见：​​这里​​

package com.knife.router4j.example.order.config;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;

@Configuration
public class LoadBalancerClientConfiguration {

  @Bean
  public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
                                           LoadBalancerClientFactory loadBalancerClientFactory) {
    String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    return new RandomLoadBalancer(
        loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
  }
}