01 Detailed explanation of the functions, implementation, classification and workflow of Gateway service gateway

Gateway Service Gateway

`网关功能`

Gateway is the unified entrance for all microservices. The core functional characteristics of the gateway are mainly reflected in请求路由,权限控制,限流three parts

Routing: Since the gateway cannot process the business, the gateway needs to forward the request to the matching host or interface according to a certain method规则(断言). This forwarding The process is called routing
负载均衡: When the routing target microservice has multiple instances, you also need to select one from the multiple service instances through load balancing rules.
身份认证(鉴权): As the entrance to microservices, the gateway needs to verify whether the user is qualified to request or has the permission to perform the operation. If not, it will be intercepted.
访问控制: Set up black and white lists, such as restricting IP addresses for DDOS attacks
请求限流: When the request volume is too high, the gateway will release the request at the speed that the microservice can accept to avoid excessive service pressure.
Release control: For example, when a new interface is launched, 20% of the traffic will be allocated to the new interface first, and 80% will be allocated to the old interface, and the proportion will be adjusted slowly later
[Traffic coloring](https://docs.spring.io/spring-cloud-gateway/docs/current/refer
ence/html/#the-addrequestheader-gatewayfilter -factory): Distinguish user sources and add some identifiers to requests, usually by adding new request headers,global dyeing
Unified handling of cross-domain: The gateway handles cross-domain in a unified manner, without having to handle each project separately
Unified business processing: Put the common logic required in each project into the upper gateway for unified processing
Unified document knife4j: It is recommended to aggregate the documents of downstream projects on one page for unified viewing
统一日志: Unified request and response information records
接口保护: Restriction request,Information desensitization,< /span>Set the timeout and interrupt when it times out,Request current limit (token bucket algorithm, leaky bucket algorithm, RedisLimitHandler),Downgrade circuit breaker for cover-up

`网关的分类`

Classification of gateways and their technology selection

全局网关(接入层网关): Mainly implements load balancing, request logs, etc., and is not bound to business logic code
业务网关(微服务网关): Forward requests to different businesses/projects/interfaces/services, including some business logic code

There are mainly four types of gateway implementations in Spring Cloud, which are designed to provide a simple and effective unified API routing management method for the microservice framework.

Spring Cloud Gateway: A brand new project of SpringCloud, a gateway developed based on reactive programming and event streaming technologies such as Spring 5.0, SpringBoot2.0 and ProjectReactor.
Zuul: It is a blocking programming implementation based on Servlet, and SpringCloudGateway is a responsive programming implementation based on WebFlux provided in Spring 5, so it has better performance.
其他实现: Nginx (global gateway),Kong (API gateway, programming cost is relatively high)

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`网关的实现`

Step 1: Create a new SpringBoot project such as gateway module, introduce gateway dependency and nacos service discovery dependency

<!--网关依赖-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
<!--nacos服务发现依赖-->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

Step 2: Write the startup class ingateway模块

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

编程式(更灵活): Add the corresponding gateway code to the project startup class to implement https://yupi.icu/yupi to http://yupi.icu/

@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
    
    
    return builder.routes()
        .route("toyupi", r -> r.path("/yupi")
               .uri("http://yupi.icu/"))
         .route("路由Id", r -> r.path("路由规则")
               .uri("路由的目标地址"))
         .route.......
        .build();
}

配置式(更直观):Write basic configuration and routing rules

路由名称(id): The unique representation of the route, user-defined only needs to be unique
路由目标地址(uri): You can route to a fixed address, or you can route to a service and then select a service instance according to the load balancing rules.
路由断言(predicates): Determine whether the request meets the conditions of the routing rules, and forward it to the routing destination if it does.
路由过滤器(filters): Perform some processing operations on the request or response

# 快捷配置方式
spring:
  cloud:
    gateway:
      routes:
      - id: after_route
        uri: https://example.org # 路由到固定地址
        uri: lb://Nacos中注册的服务名称 # 路由到某个服务
        predicates: 
        - Cookie=mycookie,mycookievalue  # cookie里必须有mycookie且值是mycookievalue
# 完全展开配置方式        
spring:
  cloud:
    gateway:
      routes:
      - id: after_route
        uri: https://example.org
        predicates:
        - name: Cookie
          args:
            name: mycookie
            regexp: mycookievalue

`网关的工作流程`

Step 1: The client initiates a request to the gateway. If the request matches the route defined by Handler Mapping, the request will be forwarded to Web Handler

Step 2: Filter user requests through the defined filter chain. The filter can be executed before or after the proxy request.

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