微服务-流量染色

1. 功能目的

通过设置请求头的方式将http请求优先打到指定的服务上，为微服务开发调试工作提供便利

请求报文难模拟：可以直接在测试环境页面上操作，流量直接打到本地IDEA进行debug
请求链路较长：本地开发无需启动所有服务，仅需要启动目标服务
协同开发：与其他人一同开发，并且依赖对方开发的接口，可以直接将自己本地服务的请求发到对方本地服务上
这是目前主要的使用目的，当然也可以调整负载均衡逻辑，配合网关的一些自定义配置，扩充为灰度发布的效果

2. 实现原理

通过在网关以及Ribbon，实现自定义的负载均衡策略，将请求引流到本地。
PS：需要服务器能访问本地，需要类似OpenVPN这样赋予本地一个IP，供服务器网关能请求到本地
开启OpenVPN之后本机会有多个IP，通过配置指定注册到nacos上的IP

spring.cloud.nacos.discovery.network-interface: 10.0

2.1 本地服务调整

本地启动时，配置文件添加参数，设置一个元数据作为服务的流量标识
比如mdm服务配置参数

spring.cloud.nacos.discovery.metadata.request-mark: azhuzhu

服务启动之后，我们可以在nacos的服务列表里看到元数据
在这里插入图片描述

2.2 网关负载均衡

服务分类：

服务器服务：metadata中没有 requestMark 参数
本地服务：metadata中带有 requestMark 参数

网关实现自定义负载均衡策略：

判断请求头中是否带有本地流量标识：requestMark
- 有标识：判断有无metadata匹配的服务实例
  - 有：调用匹配的服务实例
  - 无：判断目标请求有没有服务器服务实例
    - 有：服务器服务随机数负载
    - 无：可用实例随机负载
- 无标识：判断目标请求有没有服务器服务实例
  - 有：服务器服务随机数负载
  - 无：可用实例随机负载
    网关负载处理了第一目标服务，假如调用链路为 mdm -> commom-api，我们启动的是common-api，则需要在服务端的ribbon中做负载

2.3 请求发起

比如，约定request-mark作为本地流量标识
请求头 request-mark=azhuzhu 表示流量优先打到带有元数据 request-mark=azhuzhu 的服务

浏览器操作：通过浏览器插件ModHeader，在浏览器发起请求时，带上请求头
HTTP工具：带上自定义请求头

3. 具体代码介绍

以下所有注册的bean，都通过指定的配置参数开启

@ConditionalOnProperty(name = "hg.request-mark.enable", havingValue = "true")

3.1 自定义负载均衡器

网关及其他客户端的流量染色具体的负载逻辑实现

import com.google.common.collect.Lists;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.MapUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.reactive.DefaultResponse;
import org.springframework.cloud.client.loadbalancer.reactive.EmptyResponse;
import org.springframework.cloud.client.loadbalancer.reactive.Request;
import org.springframework.cloud.client.loadbalancer.reactive.Response;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClients;
import org.springframework.cloud.loadbalancer.core.NoopServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.env.Environment;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import reactor.core.publisher.Mono;

import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.stream.Collectors;

/**
 * 自定义负载均衡器 用于开发环境的流量染色
 *
 * @author 阿猪 2024-08-09 11:45
 */
@Slf4j
@Configuration
@SuppressWarnings("deprecation")
@ConditionalOnProperty(name = "hg.request-mark.enable", havingValue = "true")
@LoadBalancerClients(defaultConfiguration = {ReqMarkLoadBalancer.class})
public class ReqMarkLoadBalancer {

    public static final String REQUEST_MARK = "request-mark";

    /**
     * 开启流量染色时 替换默认的负载器
     *
     * @param environment               环境信息
     * @param loadBalancerClientFactory 负载器工厂
     * @return 自定义负载器
     */
    @Bean
    @Primary
    public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
                                                                                   LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RandomLoadBalancer(
                loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
    }

    static class RandomLoadBalancer implements ReactorServiceInstanceLoadBalancer {

        private final ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;

        private final String serviceId;

        public RandomLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
                                  String serviceId) {
            this.serviceId = serviceId;
            this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
        }

        @Override
        public Mono<Response<ServiceInstance>> choose(Request request) {
            ServiceInstanceListSupplier supplier =
                    serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
            String requestMark = getRequestMark(request);
            return supplier.get().next().map(serviceInstances -> processInstanceResponseByReqMark(serviceInstances, requestMark));
        }

        private String getRequestMark(Request<?> request) {
            // 客户端的负载 直接从 RequestContextHolder 拿请求头
            ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            if (attributes != null) {
                return attributes.getRequest().getHeader(REQUEST_MARK);
            }
            // 网关的负载从 request 取值（网关覆盖了默认实现 把context塞进去了 不然拿到是 null 跟spring boot版本有关系）
            if (!(request.getContext() instanceof ServerHttpRequest)) {
                return null;
            }
            ServerHttpRequest context = (ServerHttpRequest) request.getContext();
            if (context.getHeaders().containsKey(REQUEST_MARK)) {
                return context.getHeaders().getFirst(REQUEST_MARK);
            }
            return null;
        }

        /**
         * 默认的随机数负载
         *
         * @param instances 可用服务实例
         * @return 命中实例
         */
        private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances) {
            if (CollectionUtils.isEmpty(instances)) {
                log.warn("No instance available {}", serviceId);
                return new EmptyResponse();
            }
            Random random = new Random();
            ServiceInstance instance = instances.get(random.nextInt(instances.size()));
            return new DefaultResponse(instance);
        }

        private Response<ServiceInstance> processInstanceResponseByReqMark(List<ServiceInstance> instances, String requestMark) {
            if (instances.isEmpty()) {
                return new EmptyResponse();
            }
            ServiceInstance sameClusterNameInst = selectInstanceByReqMark(instances, requestMark);
            return new DefaultResponse(sameClusterNameInst);
        }

        private ServiceInstance selectInstanceByReqMark(List<ServiceInstance> instances, String requestMark) {
            // 元数据不带请求标识的服务, 标识为服务器上的服务
            List<ServiceInstance> serverInstances = instances.stream().filter(instance -> {
                Map<String, String> metadata = instance.getMetadata();
                return MapUtils.isEmpty(metadata) || !metadata.containsKey(REQUEST_MARK);
            }).collect(Collectors.toList());

            if (StringUtils.isBlank(requestMark)) {
                if (CollectionUtils.isEmpty(serverInstances)) {
                    return instances.get(new Random().nextInt(instances.size()));
                }
                return serverInstances.get(new Random().nextInt(serverInstances.size()));
            }

            List<ServiceInstance> matchInstances = Lists.newArrayList();
            for (ServiceInstance instance : instances) {
                Map<String, String> metadata = instance.getMetadata();
                if (MapUtils.isEmpty(metadata)) {
                    continue;
                }
                if (metadata.containsKey(REQUEST_MARK) && requestMark.equals(metadata.get(REQUEST_MARK))) {
                    matchInstances.add(instance);
                }
            }
            Random random = new Random();
            // 优先匹配到的服务  最后是随机
            if (CollectionUtils.isNotEmpty(matchInstances)) {
                return matchInstances.get(random.nextInt(matchInstances.size()));
            }
            // 然后是无标识服务(服务器上的服务)
            if (CollectionUtils.isNotEmpty(serverInstances)) {
                return serverInstances.get(random.nextInt(serverInstances.size()));
            }
            // 前两者都没有就随机获取
            return instances.get(random.nextInt(instances.size()));
        }
    }

}

3.2 流量标识请求头透传

这里使用Feign进行内部服务调用，需要将原请求的流量标识请求头继续传递下去，保证后续的服务链路也能有流量染色的效果。

import feign.RequestInterceptor;
import feign.RequestTemplate;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

/**
 * 流量染色 - 流量标识请求头透传
 *
 * @author 阿猪 2024-09-25 17:11
 */
@Component
@ConditionalOnProperty(name = "hg.request-mark.enable", havingValue = "true")
public class ReqMarkRequestInterceptor implements RequestInterceptor {

    @Override
    public void apply(RequestTemplate requestTemplate) {
        // 从 request 中获取流量标识, 设置到 feign 的 requestTemplate中
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        if (attributes != null) {
            requestTemplate.header(ReqMarkLoadBalancer.REQUEST_MARK, attributes.getRequest().getHeader(ReqMarkLoadBalancer.REQUEST_MARK));
        }
    }

}

3.3 网关负载均衡-请求信息获取

由于这个方案中，负载均衡是依靠请求头判断的，详见上面请求头的获取ReqMarkLoadBalancer.getRequestMark
在spring boot 2.3.2 版本中 request.getContext是个空的，没法获取请求信息
2.6.x 后面没有这个问题，但需要关注下这个context的类型，调整代码
以下是覆盖默认实现，为 request 的 context 设置请求信息。
实际上是复制 ReactiveLoadBalancerClientFilter的源码稍作修改，看倒数最后两行

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.reactive.DefaultRequest;
import org.springframework.cloud.client.loadbalancer.reactive.Request;
import org.springframework.cloud.client.loadbalancer.reactive.Response;
import org.springframework.cloud.gateway.config.LoadBalancerProperties;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.ReactiveLoadBalancerClientFilter;
import org.springframework.cloud.gateway.support.DelegatingServiceInstance;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import java.net.URI;

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.*;

/**
 * 覆盖默认的负载均衡器 改了choose方法 将request信息传入
 *
 * @see ReactiveLoadBalancerClientFilter
 * @author 阿猪 2024-08-09 17:06
 */
@Slf4j
@Component
@ConditionalOnProperty(name = "hg.request-mark.enable", havingValue = "true")
public class CustomLoadBalancerClientFilter extends ReactiveLoadBalancerClientFilter {

    private static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10150;

    private final LoadBalancerClientFactory clientFactory;

    private final LoadBalancerProperties properties;

    public CustomLoadBalancerClientFilter(LoadBalancerClientFactory clientFactory,
                                          LoadBalancerProperties properties) {
        super(null, null);
        this.clientFactory = clientFactory;
        this.properties = properties;
    }

    @Override
    public int getOrder() {
        return LOAD_BALANCER_CLIENT_FILTER_ORDER;
    }

    @Override
    @SuppressWarnings("Duplicates")
    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);
        }

        return choose(exchange).doOnNext(response -> {

            if (!response.hasServer()) {
                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);
        }).then(chain.filter(exchange));
    }

    @SuppressWarnings("deprecation")
    private Mono<Response<ServiceInstance>> choose(ServerWebExchange exchange) {
        URI uri = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
        ReactorLoadBalancer<ServiceInstance> loadBalancer = this.clientFactory
                .getInstance(uri.getHost(), ReactorServiceInstanceLoadBalancer.class);
        if (loadBalancer == null) {
            throw new NotFoundException("No loadbalancer available for " + uri.getHost());
        }
        // 就改了这里 仅调整参数传入 保持原有逻辑(原代码传入了空的request)
        Request<?> request = new DefaultRequest<>(exchange.getRequest());
        return loadBalancer.choose(request);
    }

}

将bean覆盖掉，替换掉原本的 ReactiveLoadBalancerClientFilter

import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.cloud.gateway.config.LoadBalancerProperties;
import org.springframework.cloud.gateway.filter.ReactiveLoadBalancerClientFilter;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * 流量染色 - 将ReactiveLoadBalancerClientFilter覆盖掉 为了获取到http请求头
 *
 * @author 阿猪 2024-08-09 17:12
 */
@Configuration
public class CustomLoadBalancerConfig {

    @Bean
    @ConditionalOnProperty(name = "hg.request-mark.enable", havingValue = "true")
    public ReactiveLoadBalancerClientFilter gatewayLoadBalancerClientFilter(LoadBalancerClientFactory clientFactory,
                                                                            LoadBalancerProperties properties){
        return new CustomLoadBalancerClientFilter(clientFactory, properties);
    }

}