SpringCloud-Gateway-Canary: A Java repository from Xlinlin

1.SpringCloud Gateway 源码导读整理

META-INF/spring.factories
GatewayClassPathWarningAutoConfiguration
- DispatcherServlet webmvc检测存在警告，DispatcherHandler webflux不存在检测警告
GatewayAutoConfiguration
- 必须是在webflux环境下DispatcherHandler
- 初始化Route相关：RouteLocatorBuilder、PropertiesRouteDefinitionLocator、InMemoryRouteDefinitionRepository、RouteLocator
- FilteringWebHandler、RouteRefreshListener、ConfigurationService、RoutePredicateHandlerMapping、WebSocketService
- 配置：GlobalCorsProperties、GatewayProperties、SecureHeadersProperties
- Filter：ForwardedHeadersFilter、RemoveHopByHopHeadersFilter、XForwardedHeadersFilter、AdaptCachedBodyGlobalFilter、RemoveCachedBodyFilter、 RouteToRequestUrlFilter、ForwardRoutingFilter、ForwardPathFilter、WebsocketRoutingFilter、WeightCalculatorWebFilter
- Predicate BeanFactory：AfterRoutePredicateFactory、BeforeRoutePredicateFactory、BetweenRoutePredicateFactory、CookieRoutePredicateFactory、 HeaderRoutePredicateFactory、HostRoutePredicateFactory、MethodRoutePredicateFactory、PathRoutePredicateFactory、QueryRoutePredicateFactory、 ReadBodyPredicateFactory、RemoteAddrRoutePredicateFactory、WeightRoutePredicateFactory、CloudFoundryRouteServiceRoutePredicateFactory
- Filter BeanFactory：AddRequestHeaderGatewayFilterFactory、MapRequestHeaderGatewayFilterFactory、AddRequestParameterGatewayFilterFactory、 AddResponseHeaderGatewayFilterFactory、ModifyRequestBodyGatewayFilterFactory、DedupeResponseHeaderGatewayFilterFactory、ModifyResponseBodyGatewayFilterFactory、 PrefixPathGatewayFilterFactory、PreserveHostHeaderGatewayFilterFactory、RedirectToGatewayFilterFactory、RemoveRequestHeaderGatewayFilterFactory、 RemoveRequestParameterGatewayFilterFactory、RemoveResponseHeaderGatewayFilterFactory、RequestRateLimiterGatewayFilterFactory、RewritePathGatewayFilterFactory、 RetryGatewayFilterFactory、SetPathGatewayFilterFactory、SecureHeadersGatewayFilterFactory、SetRequestHeaderGatewayFilterFactory、SetResponseHeaderGatewayFilterFactory、 RewriteResponseHeaderGatewayFilterFactory、RewriteLocationResponseHeaderGatewayFilterFactory、SetStatusGatewayFilterFactory、SaveSessionGatewayFilterFactory StripPrefixGatewayFilterFactory、RequestHeaderToRequestUriGatewayFilterFactory、RequestSizeGatewayFilterFactory、RequestHeaderSizeGatewayFilterFactory
- Resolver：PrincipalNameKeyResolver、GzipMessageBodyResolver
- NettyConfiguration：HttpClient、HttpClientProperties、NettyRoutingFilter、NettyWriteResponseFilter、ReactorNettyWebSocketClient、NettyWebServerFactoryCustomizer
GatewayHystrixCircuitBreakerAutoConfiguration
- Hystrix熔断：SpringCloudCircuitBreakerHystrixFilterFactory、FallbackHeadersGatewayFilterFactory
GatewayResilience4JCircuitBreakerAutoConfiguration
- Resilience4J熔断，Java8和函数式编程设计的轻量级容错框架：SpringCloudCircuitBreakerResilience4JFilterFactory、FallbackHeadersGatewayFilterFactory
GatewayLoadBalancerClientAutoConfiguration
- 负载均衡：LoadBalancerClientFilter
GatewayNoLoadBalancerClientAutoConfiguration
- 不需要负载均衡 404？
GatewayMetricsAutoConfiguration
- 监控数据：GatewayHttpTagsProvider、GatewayRouteTagsProvider、PropertiesTagsProvider、GatewayMetricsFilter
GatewayRedisAutoConfiguration
- Redis支持,redis实现限流：RedisScript、RedisRateLimiter

GatewayDiscoveryClientAutoConfiguration

注册中心做服务发现，默认

Predicat：pattern='/'+serviceId+'/**'形式
Filter：regexp='/' + serviceId + '/(?<remaining>.*)'、replacement='/${remaining}'

DiscoveryClientRouteDefinitionLocator
SimpleUrlHandlerMappingGlobalCorsAutoConfiguration
GatewayReactiveLoadBalancerClientAutoConfiguration
- 替代GatewayLoadBalancerClientAutoConfiguration？ ReactiveLoadBalancerClientFilter
请求流程
- client-> DispatcherHandler(请求调度) --> RoutePredicateHandlerMapping(lookupRoute)(路由匹配) --> SimpleHandlerAdapter --> FilteringWebHandler(filters) --> NettyRoutingFilter(proxy filter) --> services
- DispatcherHandler.initStrategies 到Contenxt上下文查找所有的HandlerMapping，走到对应的RoutePredicateHandlerMapping
- RoutePredicateHandlerMapping.lookupRoute查找路由并过滤不符合Predicate定义的路由，将路由信息设置当上下文环境中，返回gatway自定的webhandler（FilteringWebHandler） exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, getClass().getSimpleName());
  exchange.getAttributes().put(GATEWAY_ROUTE_ATTR, r);
  exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, route.getId());
- FilteringWebHandler.handle
  对所有全局GlobalFilter包装成GatewayFilter
  获取上下文中路由信息exchange.getRequiredAttribute(GATEWAY_ROUTE_ATTR)
  进行路由排序，然后执行filter调用链DefaultGatewayFilterChain(GatewayFilterChain).filter
- RouteLocator: 获取路由类型，
  - Route组成三部分：Proxy(代理信息，service)、Predicate(谓语，请求方法、path等)、Filter(自定义过滤)
  - Route的三种来源：
    - 1.RouteLocatorBuilder方式，代码中通过RouteLocatorBuilder方式构建的路由
    - 2.Properties配置方式，通过本地配置PropertiesRouteDefinitionLocator和服务发现DiscoveryClientRouteDefinitionLocator
    - 3.RouteDefinitionRepository持久存储，内置InMemoryRouteDefinitionRepository,可扩展mysql&Redis等

2.SpringCloud API Gateway+Nacos实现多版本访问：

先实现一个全局的拦截filter GrayReactiveLoadBalancerFilter，其加载的顺序Order必须与ReactiveLoadBalancerClientFilter保持一直或提前
实现一个自定义的LoadBalancer GrayLoadBalancer实现接口: ReactorServiceInstanceLoadBalancer

3.全链路多版本路由请求

webmvc+nacos+feign+ribbon版本实现
- 主要实现思路： client(header: version=v1)->webmvc->feign->ribbon->service
  - 服务注册到nacos时添加版本号元数据
```
   spring:
     application:
       name: hello-provider
     cloud:
       nacos:
         discovery:
           server-addr: localhost:8848
           metadata:
             version: v1
```
  - 通过拦截 webmvc的HandlerInterceptor将request的header保存到ThreadLocal中，以及在RequestInterceptor(Feign)做header传递
  - 在ribbon层实现自己的路由算法com.xiao.springcloud.loadbalancer.ribbon.NacosWeightedRule，通过ThreadLocal获取header进行路由
  - 客户端针对路由指定负载均衡算法：
```
service_id:
  ribbon:
    NFLoadBalancerRuleClassName: com.xiao.springcloud.loadbalancer.ribbon.NacosWeightedRule
```
  - 思考如何将com.xiao.springcloud.webmvc.consumer.loadbalancer做成通用的组件starter，供客户端直接引用
webflux 待定
- 如何做好header的在上下文传递以及在做负载均衡的时候如何做版本负载

4.参考资料
Spring Cloud Alibaba之负载均衡组件 - Ribbon

基于springcloud gateway + nacos实现灰度发布（reactive版）

Xlinlin/SpringCloud-Gateway-Canary