springcloud 的loadbalancer 轮询算法切换方法 2021.4.3

loadbalancer修改轮询方法

在做练习，整合springboot springcloud springcloud alibab中发现，最新的eureka client集成的负载均衡已经替换为spring 的loadbalancer
在此整理下基本的替换轮询算法的方法
整合的框架版本如下

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-dependencies</artifactId>
  <version>2.4.2</version>
  <type>pom</type>
  <scope>import</scope>
</dependency>
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-dependencies</artifactId>
  <version>2020.0.0</version>
  <type>pom</type>
  <scope>import</scope>
</dependency>
<dependency>
  <groupId>com.alibaba.cloud</groupId>
  <artifactId>spring-cloud-alibaba-dependencies</artifactId>
  <version>2020.0.RC1</version>
  <type>pom</type>
  <scope>import</scope>
</dependency>

看了下代码，目前好像只有两种轮询算法
RandomLoadBalancer 随机
RoundRobinLoadBalancer 轮询

• 参考 https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/#spring-cloud-loadbalancer

  • 在@SpringBootApplication 能扫描的外边设置配置类

    参考

    The classes you pass as @LoadBalancerClient or @LoadBalancerClients configuration arguments should either not be annotated with @Configuration or be outside component scan scope.
    

  • 配置类为

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

  • 可以自己定制化自己的轮询算法

    import java.util.List;
    import java.util.concurrent.ThreadLocalRandom;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.beans.factory.ObjectProvider;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.loadbalancer.DefaultResponse;
    import org.springframework.cloud.client.loadbalancer.EmptyResponse;
    import org.springframework.cloud.client.loadbalancer.Request;
    import org.springframework.cloud.client.loadbalancer.Response;
    import org.springframework.cloud.loadbalancer.core.NoopServiceInstanceListSupplier;
    import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
    import org.springframework.cloud.loadbalancer.core.SelectedInstanceCallback;
    import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
    import reactor.core.publisher.Mono;
    
    public class MyRandomLoadBalancer implements ReactorServiceInstanceLoadBalancer {
        private static final Log log = LogFactory.getLog(org.springframework.cloud.loadbalancer.core.RandomLoadBalancer.class);
        private final String serviceId;
        private ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
    
        public MyRandomLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider, String serviceId) {
            this.serviceId = serviceId;
            this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
        }
    
        public MyRandomLoadBalancer(String serviceId) {
            this.serviceId = serviceId;
        }
    
        @Override
        public Mono<Response<ServiceInstance>> choose(Request request) {
            ServiceInstanceListSupplier supplier = (ServiceInstanceListSupplier)this.serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
            return supplier.get(request).next().map((serviceInstances) -> {
                return this.processInstanceResponse(supplier, serviceInstances);
            });
        }
    
        private Response<ServiceInstance> processInstanceResponse(ServiceInstanceListSupplier supplier, List<ServiceInstance> serviceInstances) {
            Response<ServiceInstance> serviceInstanceResponse = this.getInstanceResponse(serviceInstances);
            if (supplier instanceof SelectedInstanceCallback && serviceInstanceResponse.hasServer()) {
                ((SelectedInstanceCallback)supplier).selectedServiceInstance((ServiceInstance)serviceInstanceResponse.getServer());
            }
    
            return serviceInstanceResponse;
        }
    
        private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances) {
            if (instances.isEmpty()) {
                if (log.isWarnEnabled()) {
                    log.warn("No servers available for service: " + this.serviceId);
                }
    
                return new EmptyResponse();
            } else {
                /*int index = ThreadLocalRandom.current().nextInt(instances.size());
                ServiceInstance instance = (ServiceInstance)instances.get(index);
                return new DefaultResponse(instance);*/
                return new DefaultResponse(instances.get(0));
            }
        }
    }
    这个方法中本人没做什么修改，只是把instance实例返回锁定为第一个，用于验证切换轮询策略是否成功
    

  • 在@SpringBootApplication 能扫描的范围内设置配置resttemplate的配置类

    @Configuration
    @LoadBalancerClient(name = "CLOUD-PAYMENT-SERVICE", configuration = CustomLoadBalancerConfiguration.class)
    public class RestTEmplateConfig {
    
        @Bean
        // 开启负载均衡 配合 eureka 通过服务名称调用服务
        // 使用LoadBalanced注解赋予resttemplate负载均衡的能力
        @LoadBalanced
        public RestTemplate getTestTemplate(){
            return new RestTemplate();
        }
    }
    

    注意项：

    • LoadBalancerClient(name = "CLOUD-PAYMENT-SERVICE" 名称为eureka注册的服务的名称
    • @LoadBalancerClient中的configuration = CustomLoadBalancerConfiguration.class)为扫描范围外的配置类

  • controller配置

    @RestController
    @RequestMapping("/loadbalancer")
    public class TestLoadBalancerController {
        /*集群版本，从eureka中查询指定服务*/
        public static final String paymentUrl = "http://CLOUD-PAYMENT-SERVICE";
    
        @Resource
        private RestTemplate restTemplate;
    
        @GetMapping("/payment/get/{id}")
        public CommonResult<Payment> getPaymentbyId(@PathVariable("id") String id){
            return restTemplate.getForObject(paymentUrl + "/payment/get/" + id, CommonResult.class);
        }
    }
    

    注意项：

    • "http://CLOUD-PAYMENT-SERVICE"; 这个服务名称和@LoadBalancerClient(name 配置的名称一致，为eureka注册的服务的名称