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从SpringCloud 2020 版本之后#xff0c;组件移除了除 Eureka 以外#xff0c;所有 Netflix 的相关#xff0c;包括最常用的 Ribbon Hystrix 等#xff0c;所以 SpringCloud 在 spring-cloud-commons 提供了Loadbalancer 用来替代 Ribbon。本系列就来介绍Loadbalance…背景
从SpringCloud 2020 版本之后组件移除了除 Eureka 以外所有 Netflix 的相关包括最常用的 Ribbon Hystrix 等所以 SpringCloud 在 spring-cloud-commons 提供了Loadbalancer 用来替代 Ribbon。本系列就来介绍Loadbalancer 的执行流程
项目版本:
Spring-Boot2.6.13Spring-Cloud 2021.0.5spring-cloud-alibaba 2021.0.5.0Loadbalancer 3.1.5
从项目中最常用的Feign来当做入口不了解Feign的原理也没有关系直接从Feign和Loadbalancer 的集成部分分析即可
分析
入口处
FeignBlockingLoadBalancerClient
public class FeignBlockingLoadBalancerClient implements Client {private static final Log LOG LogFactory.getLog(FeignBlockingLoadBalancerClient.class);private final Client delegate;private final LoadBalancerClient loadBalancerClient;private final LoadBalancerClientFactory loadBalancerClientFactory;Overridepublic Response execute(Request request, Request.Options options) throws IOException {//请求路径final URI originalUri URI.create(request.url());//获取到要调用的服务idString serviceId originalUri.getHost();DefaultRequestRequestDataContext lbRequest new DefaultRequest(new RequestDataContext(buildRequestData(request), hint)); SetLoadBalancerLifecycle supportedLifecycleProcessors LoadBalancerLifecycleValidator.getSupportedLifecycleProcessors(//在这步创建了每个服务的子容器 loadBalancerClientFactory.getInstances(serviceId, LoadBalancerLifecycle.class),RequestDataContext.class, ResponseData.class, ServiceInstance.class);supportedLifecycleProcessors.forEach(lifecycle - lifecycle.onStart(lbRequest)); //执行loadBalancer的负载均衡策略返回将过滤后的服务非常重要ServiceInstance instance loadBalancerClient.choose(serviceId, lbRequest);org.springframework.cloud.client.loadbalancer.ResponseServiceInstance lbResponse new DefaultResponse(instance);//省略...//将ServiceInstance进行解析后转换为真正的http方式进行远程调用服务String reconstructedUrl loadBalancerClient.reconstructURI(instance, originalUri).toString();Request newRequest buildRequest(request, reconstructedUrl);LoadBalancerProperties loadBalancerProperties loadBalancerClientFactory.getProperties(serviceId);return executeWithLoadBalancerLifecycleProcessing(delegate, options, newRequest, lbRequest, lbResponse,supportedLifecycleProcessors, loadBalancerProperties.isUseRawStatusCodeInResponseData());}protected Request buildRequest(Request request, String reconstructedUrl) {return Request.create(request.httpMethod(), reconstructedUrl, request.headers(), request.body(),request.charset(), request.requestTemplate());}private String getHint(String serviceId) {LoadBalancerProperties properties loadBalancerClientFactory.getProperties(serviceId);String defaultHint properties.getHint().getOrDefault(default, default);String hintPropertyValue properties.getHint().get(serviceId);return hintPropertyValue ! null ? hintPropertyValue : defaultHint;}}可以看到在OpenFeign中调用了loadBalancerClient.choose(serviceId, lbRequest)来实现负载均衡策略然后返回过滤后的服务ServiceInstance也就是服务的对象。我们要重点分析此过程
首先分析loadBalancerClient是怎么注入进来的呢我们先看下其结构
ServiceInstanceChooser
public interface ServiceInstanceChooser {ServiceInstance choose(String serviceId);T ServiceInstance choose(String serviceId, RequestT request);}LoadBalancerClient
public interface LoadBalancerClient extends ServiceInstanceChooser {T T execute(String serviceId, LoadBalancerRequestT request) throws IOException;T T execute(String serviceId, ServiceInstance serviceInstance, LoadBalancerRequestT request) throws IOException;URI reconstructURI(ServiceInstance instance, URI original);}可以看到ServiceInstanceChooser定义了负载均衡的方法 LoadBalancerClient则继承了ServiceInstanceChooser额外定义了execute执行和reconstructURI构建真正http请求的方法
那么LoadBalancerClient的实现是谁呢刚才的疑问中又是怎么被注入的呢其实LoadBalancerClient的实现是BlockingLoadBalancerClient在配置类BlockingLoadBalancerClientAutoConfiguration中被注入
这里既然提到了自动装配配置类那么我们就需要看下其结构来了解各个作用
# AutoConfiguration
org.springframework.boot.autoconfigure.EnableAutoConfiguration\
org.springframework.cloud.loadbalancer.config.LoadBalancerAutoConfiguration,\
org.springframework.cloud.loadbalancer.config.BlockingLoadBalancerClientAutoConfiguration,\
org.springframework.cloud.loadbalancer.config.LoadBalancerCacheAutoConfiguration,\
org.springframework.cloud.loadbalancer.security.OAuth2LoadBalancerClientAutoConfiguration,\
org.springframework.cloud.loadbalancer.config.LoadBalancerStatsAutoConfigurationLoadBalancerAutoConfiguration 是最核心最重要的配置随后会详细的分析BlockingLoadBalancerClientAutoConfiguration 上文中提高的LoadBalancerClient的实现类BlockingLoadBalancerClient就是在此装配的
BlockingLoadBalancerClientAutoConfiguration
Configuration(proxyBeanMethods false)
LoadBalancerClients
AutoConfigureAfter(LoadBalancerAutoConfiguration.class)
AutoConfigureBefore({ org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration.class,AsyncLoadBalancerAutoConfiguration.class })
ConditionalOnClass(RestTemplate.class)
public class BlockingLoadBalancerClientAutoConfiguration {BeanConditionalOnBean(LoadBalancerClientFactory.class)ConditionalOnMissingBeanpublic LoadBalancerClient blockingLoadBalancerClient(LoadBalancerClientFactory loadBalancerClientFactory) {return new BlockingLoadBalancerClient(loadBalancerClientFactory);}//省略}可以看到注入了LoadBalancerClient的实现类BlockingLoadBalancerClient。但此自动配置类的装配有很多的规则
LoadBalancerClients 此注解非常重要实现每个服务间的负载均衡配置隔离就是通过此注解后面会详细的分析AutoConfigureAfter(LoadBalancerAutoConfiguration.class)在LoadBalancerAutoConfiguration之后进行装配LoadBalancerAutoConfiguration也很重要后面也会详细的分析AutoConfigureBefore({ org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class }) 在org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration和AsyncLoadBalancerAutoConfiguration之前进行装配。注意2和3中的LoadBalancerAutoConfiguration不是一个对象2中的是在spring-cloud-loadbalancer模块中3中的是在spring-cloud-commons模块中这也是有步骤2的原因毕竟肯定是要先装配本模块下的ConditionalOnClass(RestTemplate.class)这个不是重点可以略过ConditionalOnBean(LoadBalancerClientFactory.class) 在注入时依赖了LoadBalancerClientFactoryLoadBalancerClientFactory也非常的重要后面也会进行详细的分析
上面多次提到了LoadBalancerAutoConfiguration自动装配中也有它那么现在就来分析下其流程
LoadBalancerAutoConfiguration
Configuration(proxyBeanMethods false)
LoadBalancerClients
EnableConfigurationProperties(LoadBalancerClientsProperties.class)
AutoConfigureBefore({ ReactorLoadBalancerClientAutoConfiguration.class,LoadBalancerBeanPostProcessorAutoConfiguration.class })
ConditionalOnProperty(value spring.cloud.loadbalancer.enabled, havingValue true, matchIfMissing true)
public class LoadBalancerAutoConfiguration {//依赖了LoadBalancerClientSpecification类型的对象集合private final ObjectProviderListLoadBalancerClientSpecification configurations;public LoadBalancerAutoConfiguration(ObjectProviderListLoadBalancerClientSpecification configurations) {this.configurations configurations;}BeanConditionalOnMissingBeanpublic LoadBalancerZoneConfig zoneConfig(Environment environment) {return new LoadBalancerZoneConfig(environment.getProperty(spring.cloud.loadbalancer.zone));}ConditionalOnMissingBeanBeanpublic LoadBalancerClientFactory loadBalancerClientFactory(LoadBalancerClientsProperties properties) {LoadBalancerClientFactory clientFactory new LoadBalancerClientFactory(properties);//LoadBalancerClientSpecification类型的配置类集合对象注入到NamedContextFactory实现个性化配置clientFactory.setConfigurations(this.configurations.getIfAvailable(Collections::emptyList));return clientFactory;}}可以看到此配置类的装配规则也比较复杂但大部分都和本系列要分析的内容关联性不大直接略过即可我们只关心两个地方
LoadBalancerClients 这个注解出现多次我们会做详细的分析注入了loadBalancerClientFactory这个也非常的重要随后会做详细的分析
到这里我们要解决的三个重点
LoadBalancerClients的作用ObjectProviderListLoadBalancerClientSpecification configurations的作用LoadBalancerClientFactory的作用别忘了负载均衡的执行对象BlockingLoadBalancerClient在生成时将此对象注入了进去
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