如何使用 Spring Cloud 2020 中重磅推荐的负载均衡器 Spring Cloud LoadBalancer （下文简称 SCL），如何扩展负载均衡策略？ 你将从本文中获取到答案
快速上手 SCL
- 如果项目中想使用 SCL，则仅需要添加如下 maven 依赖即可
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
个性化负载均衡策略
![SCL 内置的负载均衡策略]()
@LoadBalancerClient(value = "demo-provider", configuration = RandomLoadbalancerConfig.class)
public class RandomLoadbalancerConfig {
@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);
}
}
自定义负载均衡策略
@Slf4j
public class GrayRoundRobinLoadBalancer extends RoundRobinLoadBalancer {
private ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
private String serviceId;
@Override
public Mono<Response<ServiceInstance>> choose(Request request) {
ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
.getIfAvailable(NoopServiceInstanceListSupplier::new);
return supplier.get(request).next().map(serviceInstances -> getInstanceResponse(serviceInstances, request));
}
Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances, Request request) {
// 注册中心无可用实例 抛出异常
if (CollUtil.isEmpty(instances)) {
log.warn("No instance available {}", serviceId);
return new EmptyResponse();
}
DefaultRequestContext requestContext = (DefaultRequestContext) request.getContext();
RequestData clientRequest = (RequestData) requestContext.getClientRequest();
HttpHeaders headers = clientRequest.getHeaders();
String reqVersion = headers.getFirst(CommonConstants.VERSION);
if (StrUtil.isBlank(reqVersion)) {
return super.choose(request).block();
}
// 遍历可以实例元数据，若匹配则返回此实例
for (ServiceInstance instance : instances) {
NacosServiceInstance nacosInstance = (NacosServiceInstance) instance;
Map<String, String> metadata = nacosInstance.getMetadata();
String targetVersion = MapUtil.getStr(metadata, CommonConstants.VERSION);
if (reqVersion.equalsIgnoreCase(targetVersion)) {
log.debug("gray requst match success :{} {}", reqVersion, nacosInstance);
return new DefaultResponse(nacosInstance);
}
}
// 降级策略，使用轮询策略
return super.choose(request).block();
}
}
@LoadBalancerClient(value = "demo-provider", configuration = GrayRoundLoadbalancerConfig.class)
![]()
curl --location --request GET 'http://localhost:6060/req?key=b' \
--header 'VERSION: b'
优化负载均衡策略注入
- 如上文所述，所有的个性化负载策略都需要手动通过
LoadBalancerClient 注入非常的不方便。 我们可以参考 LoadBalancerClients 的批量注入逻辑构造自己的 BeanRegistrar
![]()
public class GrayLoadBalancerClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
Field[] fields = ReflectUtil.getFields(ServiceNameConstants.class);
// 遍历服务名称，注入支持灰度策略的负载均衡器
for (Field field : fields) {
Object fieldValue = ReflectUtil.getFieldValue(ServiceNameConstants.class, field);
registerClientConfiguration(registry, fieldValue, GrayLoadBalancerClientConfiguration.class);
}
}
}
>>> 源码 https://gitee.com/log4j/pig，欢迎署名转载 <<<
