标签：return ATTR exchange GATEWAY Nacos Gateway new SpringCloudAlibaba response

官方git：https://github.com/spring-cloud/spring-cloud-gateway
Spring Cloud Gateway网关是用来代替zuul1.x作为微服务架构中的网关组件，zuul1.x是最早的网关组件，由于使用单线程阻塞式链接，所以性能有问题，gateway是搭建在webflux框架之上的响应式网关服务，底层使用Netty框架作为通讯框架。zuul2.x也使用了Netty。性能上gateway是zuul1.x的1.5~2倍，与zuul2.x相当。
我们使用的是spring-cloud-alibaba的2021.1版本，还踩了一个小小的坑，下面说。

什么是gateway

我个人理解gateway就是一个业务nginx，它支持请求转发，负载均衡，统一埋点，限流降级、安全认证等等很多功能，gateway收集所有请求根据路由规则转发请求，使用统一的过滤器处理请求参数等，是不是听起来有点像nginx，但是比nginx拥有更多功能。

gateway三大组件

如何使用

springcloud 提供了gateway的springboot版本启动器，我们可以很方便的创建一个网关项目
首先创建一个springboot项目，引入依赖

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

修改application.yml配置

server:
  port: 9000
spring:
  application:
    name: gateway-web
  cloud:
    gateway:
      discovery:
        routes:
        - id: demo-1
          uri: 127.0.0.1:9004
          predicates:
            - Path=/demo/** ##基于Path匹配的路由规则 还有其他的路由规则

集成Nacos 实现动态路由

引入依赖

		<dependency>
			<groupId>com.alibaba.cloud</groupId>
			<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
		</dependency>
		<!-- Spring Cloud 2020 中重磅推荐的负载均衡器 Spring Cloud LoadBalancer 不引用无法实现动态路由  -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-loadbalancer</artifactId>
		</dependency>

修改application.yml配置

server:
  port: 9000
spring:
  application:
    name: gateway-web
  cloud:
    gateway:
      discovery:
        routes:
        - id: demo-1
          uri: lb://demo-web   ##'lb://'代表发现注册中心的服务 'demo-web'服务提供方的name 
          predicates:
            - Path=/demo/**
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
        password: nacos
        username: nacos

启动类增加服务发现注解

@SpringBootApplication
@EnableDiscoveryClient
public class GatewayWebApplication {

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

}

可以自nacos中发现该gateway服务

基于约定的服务动态路由 自动配置routes

修改application.yml配置

server:
  port: 9000
spring:
  application:
    name: gateway-web
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true ##开启自动发现
          lower-case-service-id: true ##转小写
#      routes:
#        - id: demo-1
#          uri: lb://demo-web
#          predicates:
#            - Path=/demo/**
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
        password: nacos
        username: nacos

注意这里在访问服务的时候需要添加一级以服务名称为路径的资源
比如：http://127.0.0.1:9004/demo/userinfo
要访问 http://127.0.0.1:9004/demo-web/demo/userinfo demo-web为服务提供方的name

2021.1版本踩坑

网上很多教程都没有提示需要引入spring-cloud-starter-loadbalance，可能文章都比较老，loadbalance是2020版本提供的负载均衡器，这里是默认使用的，所以不引用就没办反实现动态路由，连个日志都没有，害我debug半天。
说几个在服务转发中几个比较重要的组件：

DispatcherHandler 入口

@Override
	public Mono<Void> handle(ServerWebExchange exchange) {
		if (this.handlerMappings == null) {
			return createNotFoundError();
		}
		return Flux.fromIterable(this.handlerMappings)
				.concatMap(mapping -> mapping.getHandler(exchange))
				.next()
				.switchIfEmpty(createNotFoundError())
				.flatMap(handler -> invokeHandler(exchange, handler))
				.flatMap(result -> handleResult(exchange, result));
	}

RoutePredicateHandlerMapping 负责获取所有路由规则

	@Override
	protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
		// don't handle requests on management port if set and different than server port
		if (this.managementPortType == DIFFERENT && this.managementPort != null
				&& exchange.getRequest().getURI().getPort() == this.managementPort) {
			return Mono.empty();
		}
		exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, getSimpleName());

		return lookupRoute(exchange)
				// .log("route-predicate-handler-mapping", Level.FINER) //name this
				.flatMap((Function<Route, Mono<?>>) r -> {
					exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
					if (logger.isDebugEnabled()) {
						logger.debug("Mapping [" + getExchangeDesc(exchange) + "] to " + r);
					}

					exchange.getAttributes().put(GATEWAY_ROUTE_ATTR, r);
					return Mono.just(webHandler);
				}).switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> {
					exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
					if (logger.isTraceEnabled()) {
						logger.trace("No RouteDefinition found for [" + getExchangeDesc(exchange) + "]");
					}
				})));
	}

FilteringWebHandler 执行过滤器链

	@Override
	public Mono<Void> handle(ServerWebExchange exchange) {
		Route route = exchange.getRequiredAttribute(GATEWAY_ROUTE_ATTR);
		List<GatewayFilter> gatewayFilters = route.getFilters();

		List<GatewayFilter> combined = new ArrayList<>(this.globalFilters);
		combined.addAll(gatewayFilters);
		// TODO: needed or cached?
		AnnotationAwareOrderComparator.sort(combined);

		if (logger.isDebugEnabled()) {
			logger.debug("Sorted gatewayFilterFactories: " + combined);
		}

		return new DefaultGatewayFilterChain(combined).filter(exchange);
	}

RouteToRequestUrlFilter 负责根据路由规则转换url

@Override
	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
		Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
		if (route == null) {
			return chain.filter(exchange);
		}
		log.trace("RouteToRequestUrlFilter start");
		URI uri = exchange.getRequest().getURI();
		boolean encoded = containsEncodedParts(uri);
		URI routeUri = route.getUri();

		if (hasAnotherScheme(routeUri)) {
			// this is a special url, save scheme to special attribute
			// replace routeUri with schemeSpecificPart
			exchange.getAttributes().put(GATEWAY_SCHEME_PREFIX_ATTR, routeUri.getScheme());
			routeUri = URI.create(routeUri.getSchemeSpecificPart());
		}

		if ("lb".equalsIgnoreCase(routeUri.getScheme()) && routeUri.getHost() == null) {
			// Load balanced URIs should always have a host. If the host is null it is
			// most
			// likely because the host name was invalid (for example included an
			// underscore)
			throw new IllegalStateException("Invalid host: " + routeUri.toString());
		}

		URI mergedUrl = UriComponentsBuilder.fromUri(uri)
				// .uri(routeUri)
				.scheme(routeUri.getScheme()).host(routeUri.getHost()).port(routeUri.getPort()).build(encoded).toUri();
		exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, mergedUrl);
		return chain.filter(exchange);
	}

ReactiveLoadBalancerClientFilter 负责对远程分布式服务做负载均衡

以前使用的是LoadBalancerClientFilter

@Override
	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
		URI url = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
		String schemePrefix = exchange.getAttribute(GATEWAY_SCHEME_PREFIX_ATTR);
		if (url == null || (!"lb".equals(url.getScheme()) && !"lb".equals(schemePrefix))) {
			return chain.filter(exchange);
		}
		// preserve the original url
		addOriginalRequestUrl(exchange, url);

		if (log.isTraceEnabled()) {
			log.trace(ReactiveLoadBalancerClientFilter.class.getSimpleName() + " url before: " + url);
		}

		URI requestUri = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
		String serviceId = requestUri.getHost();
		Set<LoadBalancerLifecycle> supportedLifecycleProcessors = LoadBalancerLifecycleValidator
				.getSupportedLifecycleProcessors(clientFactory.getInstances(serviceId, LoadBalancerLifecycle.class),
						RequestDataContext.class, ResponseData.class, ServiceInstance.class);
		DefaultRequest<RequestDataContext> lbRequest = new DefaultRequest<>(new RequestDataContext(
				new RequestData(exchange.getRequest()), getHint(serviceId, loadBalancerProperties.getHint())));
		return choose(lbRequest, serviceId, supportedLifecycleProcessors).doOnNext(response -> {

			if (!response.hasServer()) {
				supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
						.onComplete(new CompletionContext<>(CompletionContext.Status.DISCARD, lbRequest, response)));
				throw NotFoundException.create(properties.isUse404(), "Unable to find instance for " + url.getHost());
			}

			ServiceInstance retrievedInstance = response.getServer();

			URI uri = exchange.getRequest().getURI();

			// if the `lb:<scheme>` mechanism was used, use `<scheme>` as the default,
			// if the loadbalancer doesn't provide one.
			String overrideScheme = retrievedInstance.isSecure() ? "https" : "http";
			if (schemePrefix != null) {
				overrideScheme = url.getScheme();
			}

			DelegatingServiceInstance serviceInstance = new DelegatingServiceInstance(retrievedInstance,
					overrideScheme);

			URI requestUrl = reconstructURI(serviceInstance, uri);

			if (log.isTraceEnabled()) {
				log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
			}
			exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
			exchange.getAttributes().put(GATEWAY_LOADBALANCER_RESPONSE_ATTR, response);
			supportedLifecycleProcessors.forEach(lifecycle -> lifecycle.onStartRequest(lbRequest, response));
		}).then(chain.filter(exchange))
				.doOnError(throwable -> supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
						.onComplete(new CompletionContext<ResponseData, ServiceInstance, RequestDataContext>(
								CompletionContext.Status.FAILED, throwable, lbRequest,
								exchange.getAttribute(GATEWAY_LOADBALANCER_RESPONSE_ATTR)))))
				.doOnSuccess(aVoid -> supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
						.onComplete(new CompletionContext<ResponseData, ServiceInstance, RequestDataContext>(
								CompletionContext.Status.SUCCESS, lbRequest,
								exchange.getAttribute(GATEWAY_LOADBALANCER_RESPONSE_ATTR),
								new ResponseData(exchange.getResponse(), new RequestData(exchange.getRequest()))))));
	}

NettyRoutingFilter 负责通讯 使用HttpClient进行请求的发送

@Override
	@SuppressWarnings("Duplicates")
	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) -> {

			// Defer committing the response until all route filters have run
			// Put client response as ServerWebExchange attribute and write
			// response later NettyWriteResponseFilter
			exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);
			exchange.getAttributes().put(CLIENT_RESPONSE_CONN_ATTR, connection);

			ServerHttpResponse response = exchange.getResponse();
			// put headers and status so filters can modify the response
			HttpHeaders headers = new HttpHeaders();

			res.responseHeaders().forEach(entry -> headers.add(entry.getKey(), entry.getValue()));

			String contentTypeValue = headers.getFirst(HttpHeaders.CONTENT_TYPE);
			if (StringUtils.hasLength(contentTypeValue)) {
				exchange.getAttributes().put(ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR, contentTypeValue);
			}

			setResponseStatus(res, response);

			// make sure headers filters run after setting status so it is
			// available in response
			HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(getHeadersFilters(), headers, exchange,
					Type.RESPONSE);

			if (!filteredResponseHeaders.containsKey(HttpHeaders.TRANSFER_ENCODING)
					&& filteredResponseHeaders.containsKey(HttpHeaders.CONTENT_LENGTH)) {
				// It is not valid to have both the transfer-encoding header and
				// the content-length header.
				// Remove the transfer-encoding header in the response if the
				// content-length header is present.
				response.getHeaders().remove(HttpHeaders.TRANSFER_ENCODING);
			}

			exchange.getAttributes().put(CLIENT_RESPONSE_HEADER_NAMES, filteredResponseHeaders.keySet());

			response.getHeaders().putAll(filteredResponseHeaders);

			return Mono.just(res);
		});

		Duration responseTimeout = getResponseTimeout(route);
		if (responseTimeout != null) {
			responseFlux = responseFlux
					.timeout(responseTimeout,
							Mono.error(new TimeoutException("Response took longer than timeout: " + responseTimeout)))
					.onErrorMap(TimeoutException.class,
							th -> new ResponseStatusException(HttpStatus.GATEWAY_TIMEOUT, th.getMessage(), th));
		}

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

NettyWriteResponseFilter 处理response

	@Override
	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
		// NOTICE: nothing in "pre" filter stage as CLIENT_RESPONSE_CONN_ATTR is not added
		// until the NettyRoutingFilter is run
		// @formatter:off
		return chain.filter(exchange)
				.doOnError(throwable -> cleanup(exchange))
				.then(Mono.defer(() -> {
					Connection connection = exchange.getAttribute(CLIENT_RESPONSE_CONN_ATTR);

					if (connection == null) {
						return Mono.empty();
					}
					if (log.isTraceEnabled()) {
						log.trace("NettyWriteResponseFilter start inbound: "
								+ connection.channel().id().asShortText() + ", outbound: "
								+ exchange.getLogPrefix());
					}
					ServerHttpResponse response = exchange.getResponse();

					// TODO: needed?
					final Flux<DataBuffer> body = connection
							.inbound()
							.receive()
							.retain()
							.map(byteBuf -> wrap(byteBuf, response));

					MediaType contentType = null;
					try {
						contentType = response.getHeaders().getContentType();
					}
					catch (Exception e) {
						if (log.isTraceEnabled()) {
							log.trace("invalid media type", e);
						}
					}
					return (isStreamingMediaType(contentType)
							? response.writeAndFlushWith(body.map(Flux::just))
							: response.writeWith(body));
				})).doOnCancel(() -> cleanup(exchange));
		// @formatter:on
	}

标签：return,ATTR,exchange,GATEWAY,Nacos,Gateway,new,SpringCloudAlibaba,response
来源： https://blog.csdn.net/weixin_45678031/article/details/118073028

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