@RibbonClients(value ={
        //只對文章服務進行灰度發(fā)布
        @RibbonClient(value = "article-server",configuration = GrayRuleConfig.class)
} )
@SpringBootApplication
public class GatewayApplication {
   
}

public class GlobalGrayFilter implements GlobalFilter{
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain){
         //① 解析請求頭，查看是否存在灰度發(fā)布的請求頭信息，如果存在則將其放置在ThreadLocal中
        HttpHeaders headers = exchange.getRequest().getHeaders();
        if (headers.containsKey(GrayConstant.GRAY_HEADER)){
            String gray = headers.getFirst(GrayConstant.GRAY_HEADER);
            if (StrUtil.equals(gray,GrayConstant.GRAY_VALUE)){
                //②設置灰度標記
                GrayRequestContextHolder.setGrayTag(true);
            }
        }
       //③ 將灰度標記放入請求頭中
   ServerHttpRequest tokenRequest = exchange.getRequest().mutate()
    //將灰度標記傳遞過去
    .header(GrayConstant.GRAY_HEADER,GrayRequestContextHolder.getGrayTag().toString())
    .build();
            ServerWebExchange build = exchange.mutate().request(tokenRequest).build();
            return chain.filter(build);
    }
}

/**
 * 灰度發(fā)布的規(guī)則
 */
public class GrayRule extends ZoneAvoidanceRule {

    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig){
    }

    @Override
    public Server choose(Object key){
        try {
            //從ThreadLocal中獲取灰度標記
            boolean grayTag = GrayRequestContextHolder.getGrayTag().get();
            //獲取所有可用服務
            List<Server> serverList = this.getLoadBalancer().getReachableServers();
            //灰度發(fā)布的服務
            List<Server> grayServerList = new ArrayList<>();
            //正常的服務
            List<Server> normalServerList = new ArrayList<>();
            for(Server server : serverList) {
                NacosServer nacosServer = (NacosServer) server;
                //從nacos中獲取元素劇進行匹配
                if(nacosServer.getMetadata().containsKey(GrayConstant.GRAY_HEADER)
                        && nacosServer.getMetadata().get(GrayConstant.GRAY_HEADER).equals(GrayConstant.GRAY_VALUE)) {
                    grayServerList.add(server);
                } else {
                    normalServerList.add(server);
                }
            }
            //如果被標記為灰度發(fā)布，則調用灰度發(fā)布的服務
            if(grayTag) {
                return originChoose(grayServerList,key);
            } else {
                return originChoose(normalServerList,key);
            }
        } finally {
            //清除灰度標記
            GrayRequestContextHolder.remove();
        }
    }

    private Server originChoose(List<Server> noMetaServerList, Object key){
        Optional<Server> server = getPredicate().chooseRoundRobinAfterFiltering(noMetaServerList, key);
        if (server.isPresent()) {
            return server.get();
        } else {
            return null;
        }
    }
}

/**
 * 灰度部署的負載規(guī)則配置類
 * 注意：這個類一定不要被Spring Boot 掃描進入IOC容器中，一旦掃描進入則對全部的服務都將生效
 */
public class GrayRuleConfig {
    @Bean
    public GrayRule grayRule(){
        return new GrayRule();
    }
}

@Component
@Slf4j
public class FeignRequestInterceptor implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate template){
        HttpServletRequest httpServletRequest = RequestContextUtils.getRequest();
        Map<String, String> headers = getHeaders(httpServletRequest);
        for (Map.Entry<String, String> entry : headers.entrySet()) {
            //② 設置請求頭到新的Request中
            template.header(entry.getKey(), entry.getValue());
        }
    }

    /**
     * 獲取原請求頭
     */
    private Map<String, String> getHeaders(HttpServletRequest request){
        Map<String, String> map = new LinkedHashMap<>();
        Enumeration<String> enumeration = request.getHeaderNames();
        if (enumeration != null) {
            while (enumeration.hasMoreElements()) {
                String key = enumeration.nextElement();
                String value = request.getHeader(key);
                //將灰度標記的請求頭透傳給下個服務
                if (StrUtil.equals(GrayConstant.GRAY_HEADER,key)&&Boolean.TRUE.toString().equals(value)){
                    //① 保存灰度發(fā)布的標記
                    GrayRequestContextHolder.setGrayTag(true);
                    map.put(key, value);
                }
            }
        }
        return map;
    }
}

@RibbonClients(value = {
        //指定對comments這個服務開啟灰度部署
        @RibbonClient(value = "comments",configuration = GrayRuleConfig.class)
})
public class ArticleApplication {}

spring:
  cloud:
    nacos:
      discovery:
        metadata:
          ## 灰度標記
          grayTag: true