网关Spring Cloud Gateway

2021-08-17 本文已影响0人勤_

概述

spring cloud gateway提供了一个构建在 Spring 生态系统之上的 API 网关，包括：Spring 5、Spring Boot 2 和 Project Reactor。 Spring Cloud Gateway 旨在提供一种简单而有效的方式来路由到 API 并为它们提供交叉关注点，例如：安全性、监控/指标和弹性。

Route: The basic building block of the gateway. It is defined by an ID, a destination URI, a collection of predicates, and a collection of filters. A route is matched if the aggregate predicate is true.
Predicate: This is a Java 8 Function Predicate. The input type is a Spring Framework ServerWebExchange. This lets you match on anything from the HTTP request, such as headers or parameters.
Filter: These are instances of GatewayFilter that have been constructed with a specific factory. Here, you can modify requests and responses before or after sending the downstream request.

spring_cloud_gateway_diagram.png

依赖的框架以及版本

工具	版本
spring-boot	2.5.0
spring-cloud	2020.0.1
Spring Cloud Alibaba	2021.1
nacos	2.0.3

实现步骤

1，spring cloud gateway与nacos集成两步~

添加依赖

<properties>
   <java.version>1.8</java.version>
   <spring-cloud.version>2020.0.1</spring-cloud.version>
   <spring-cloud-alibaba.version>2021.1</spring-cloud-alibaba.version>
</properties>
<dependencies>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-gateway</artifactId>
   </dependency>
   <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
   </dependency>
   <dependency>
      <groupId>com.alibaba.cloud</groupId>
      <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-loadbalancer</artifactId>
   </dependency>
</dependencies>
<dependencyManagement>
   <dependencies>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-dependencies</artifactId>
         <version>${spring-cloud.version}</version>
         <type>pom</type>
         <scope>import</scope>
      </dependency>
      <dependency>
         <groupId>com.alibaba.cloud</groupId>
         <artifactId>spring-cloud-alibaba-dependencies</artifactId>
         <version>${spring-cloud-alibaba.version}</version>
         <type>pom</type>
         <scope>import</scope>
      </dependency>
   </dependencies>
</dependencyManagement>

配置application.yml文件，无需配置到bootstrap.yml文件中了，新版本nacos配置会报错。

spring:
  application:
    name: gateway
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
          lower-case-service-id: true
#      routes:
#        - id: header_route
#          uri: lb://archetype
#          predicates:
#            - Header=X-Request-Id, \d+
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
        namespace: lqd
        password: nacos
        username: nacos

Postman验证：
image-20210817094935112.png

2，了解下Route、Predicates、Filter

Route、Predicates 验证：Route Predicate Factories The Header Route Predicate Factory 请求头过滤添加如下配置，通过Postman请求验证
```
routes:
  - id: header_route
    uri: lb://archetype
    predicates:
      - Header=X-Request-Id, \d+
```
image-20210817095807823.png image-20210817095846592.png

Filter验证The AddResponseHeader GatewayFilter Factory

routes:
  - id: header_route
    uri: lb://archetype
    predicates:
      - Header=X-Request-Id, \d+
    filters:
      - AddResponseHeader=X-Response-TIME, 20210817

image-20210817103422397.png

关键源码

Predicate的核心类RoutePredicateHandlerMapping、AbstractRoutePredicateFactory

RoutePredicateHandlerMapping

protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
   return this.routeLocator.getRoutes()
         // individually filter routes so that filterWhen error delaying is not a
         // problem
         .concatMap(route -> Mono.just(route).filterWhen(r -> {
            // add the current route we are testing
            exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, r.getId());
            return r.getPredicate().apply(exchange);
         })
               // instead of immediately stopping main flux due to error, log and
               // swallow it
               .doOnError(e -> logger.error("Error applying predicate for route: " + route.getId(), e))
               .onErrorResume(e -> Mono.empty()))
         // .defaultIfEmpty() put a static Route not found
         // or .switchIfEmpty()
         // .switchIfEmpty(Mono.<Route>empty().log("noroute"))
         .next()
         // TODO: error handling
         .map(route -> {
            if (logger.isDebugEnabled()) {
               logger.debug("Route matched: " + route.getId());
            }
            validateRoute(route, exchange);
            return route;
         });

   /*
    * TODO: trace logging if (logger.isTraceEnabled()) {
    * logger.trace("RouteDefinition did not match: " + routeDefinition.getId()); }
    */
}

Filter核心类DefaultGatewayFilterChain、核心接口GlobalFilter、代理请求转发类NettyRoutingFilter

DefaultGatewayFilterChain这个类可以看到springCloud的Filter的责任链。

@Override
public Mono<Void> filter(ServerWebExchange exchange) {
   return Mono.defer(() -> {
      if (this.index < filters.size()) {
         GatewayFilter filter = filters.get(this.index);
         DefaultGatewayFilterChain chain = new DefaultGatewayFilterChain(this, this.index + 1);
         return filter.filter(exchange, chain);
      }
      else {
         return Mono.empty(); // complete
      }
   });
}

例如：RouteToRequestUrlFilter通过这个类可以方便查看到路由后的访问路径。

NettyRoutingFilter这个类是gateway转发服务到代理服务的处理类

public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
   URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);

   String scheme = requestUrl.getScheme();
   if (isAlreadyRouted(exchange) || (!"http".equals(scheme) && !"https".equals(scheme))) {
      return chain.filter(exchange);
   }
   setAlreadyRouted(exchange);

   ServerHttpRequest request = exchange.getRequest();

   final HttpMethod method = HttpMethod.valueOf(request.getMethodValue());
   final String url = requestUrl.toASCIIString();

   HttpHeaders filtered = filterRequest(getHeadersFilters(), exchange);

   final DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
   filtered.forEach(httpHeaders::set);

   boolean preserveHost = exchange.getAttributeOrDefault(PRESERVE_HOST_HEADER_ATTRIBUTE, false);
   Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);

   Flux<HttpClientResponse> responseFlux = getHttpClient(route, exchange).headers(headers -> {
      headers.add(httpHeaders);
      // Will either be set below, or later by Netty
      headers.remove(HttpHeaders.HOST);
      if (preserveHost) {
         String host = request.getHeaders().getFirst(HttpHeaders.HOST);
         headers.add(HttpHeaders.HOST, host);
      }
   }).request(method).uri(url).send((req, nettyOutbound) -> {
      if (log.isTraceEnabled()) {
         nettyOutbound.withConnection(connection -> log.trace("outbound route: "
               + connection.channel().id().asShortText() + ", inbound: " + exchange.getLogPrefix()));
      }
      return nettyOutbound.send(request.getBody().map(this::getByteBuf));
   }).responseConnection((res, connection) -> {
......

   return responseFlux.then(chain.filter(exchange));
}

异常报错

1，出现503 Service Unavailable

解决方法：增加spring-cloud-starter-loadbalancer依赖

<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

参考

spring cloud 与 spring cloud alibaba 版本对应关系
 spring cloud gateway
Reactor 3
Spring 5 WebFlux
例子

网关Spring Cloud Gateway

概述

依赖的框架以及版本

实现步骤

关键源码

异常报错

参考

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