背景：

當我們使用微服務時，若想在本地聯調就需要啟動多個服務，為了避免本地啟動過多服務，現將註冊中心等基礎服務共用。當我們在服務A開發時，都是註冊到同一個nacos，這樣本地和開發環境的服務A就會同時存在，當呼叫服務時就會使用負載均衡選擇服務，導致我們無法正常除錯介面。這時我們可以選擇使用灰度版本來進行服務的選擇。

具體實現步驟如下：

1、我們在本地配置檔案中新增版本頭

這樣我們服務註冊到nacos中點選服務列表會發現服務中都會帶VERSION

spring:
  cloud:
    nacos:
      discovery:
        metadata:
          VERSION: zhangsan
 

2、新增灰度服務介面

public interface GrayLoadBalancer {

	/**
	 * 根據serviceId 篩選可用服務
	 * @param serviceId 服務ID
	 * @param request 當前請求
	 * @return ServiceInstance
	 */
	ServiceInstance choose(String serviceId, ServerHttpRequest request);

}

3、灰度過濾器

import lombok.extern.slf4j.Slf4j;
import org.apache.http.util.Asserts;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.DefaultResponse;
import org.springframework.cloud.client.loadbalancer.LoadBalancerUriTools;
import org.springframework.cloud.client.loadbalancer.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.gateway.support.ServerWebExchangeUtils;
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;

@Slf4j
@Component
public class GrayReactiveLoadBalancerClientFilter extends ReactiveLoadBalancerClientFilter {

    private final static String SCHEME = "lb";

    private static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10150;
    private final GrayLoadBalancer grayLoadBalancer;
    private final LoadBalancerProperties loadBalancerProperties;

    public GrayReactiveLoadBalancerClientFilter(LoadBalancerClientFactory clientFactory, LoadBalancerProperties loadBalancerProperties, GrayLoadBalancer grayLoadBalancer) {
        super(clientFactory, loadBalancerProperties);
        this.loadBalancerProperties = loadBalancerProperties;
        this.grayLoadBalancer = grayLoadBalancer;
    }

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

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        URI url = exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR);
        String schemePrefix = exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR);

        // 直接放行
        if (url == null || (!SCHEME.equals(url.getScheme()) && !SCHEME.equals(schemePrefix))) {
            return chain.filter(exchange);
        }
        // 保留原始url
        ServerWebExchangeUtils.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(loadBalancerProperties.isUse404(),
                        "Unable to find instance for " + url.getHost());
            }

            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 = null;
            if (schemePrefix != null) {
                overrideScheme = url.getScheme();
            }

            DelegatingServiceInstance serviceInstance = new DelegatingServiceInstance(response.getServer(),
                    overrideScheme);

            URI requestUrl = LoadBalancerUriTools.reconstructURI(serviceInstance, uri);

            if (log.isTraceEnabled()) {
                log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
            }
            exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR, requestUrl);
        }).then(chain.filter(exchange));
    }

    /**
     * 獲取例項
     * @param exchange ServerWebExchange
     * @return ServiceInstance
     */
    private Mono<Response<ServiceInstance>> choose(ServerWebExchange exchange) {
        URI uri = exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR);
        Asserts.notNull(uri, "uri");
        ServiceInstance serviceInstance = grayLoadBalancer.choose(uri.getHost(), exchange.getRequest());
        return Mono.just(new DefaultResponse(serviceInstance));
    }

}

 

4、基於客戶端版本號灰度路由

當我們呼叫服務帶版本號時會優先匹配帶版本號的服務，若找不到則會隨機選擇一個服務

import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.map.MapUtil;
import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.util.StrUtil;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;

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

@Slf4j
@RequiredArgsConstructor
@Component
public class VersionGrayLoadBalancer implements GrayLoadBalancer {

	private final DiscoveryClient discoveryClient;

	/**
	 * 根據serviceId 篩選可用服務
	 * @param serviceId 服務ID
	 * @param request 當前請求
	 * @return ServiceInstance
	 */
	@Override
	public ServiceInstance choose(String serviceId, ServerHttpRequest request) {
		List<ServiceInstance> instances = discoveryClient.getInstances(serviceId);

		// 註冊中心無例項 丟擲異常
		if (CollUtil.isEmpty(instances)) {
			log.warn("No instance available for {}", serviceId);
			throw new NotFoundException("No instance available for " + serviceId);
		}

		// 獲取請求version，無則隨機返回可用例項
		String reqVersion = request.getHeaders().getFirst(CommonConstant.VERSION);
		if (StrUtil.isBlank(reqVersion)) {
			return instances.get(RandomUtil.randomInt(instances.size()));
		}

		// 遍歷可以例項元資料，若匹配則返回此例項
		List<ServiceInstance> availableList = instances.stream()
				.filter(instance -> reqVersion
						.equalsIgnoreCase(MapUtil.getStr(instance.getMetadata(), CommonConstant.VERSION)))
				.collect(Collectors.toList());

		if (CollUtil.isEmpty(availableList)) {
			return instances.get(RandomUtil.randomInt(instances.size()));
		}
		return availableList.get(RandomUtil.randomInt(availableList.size()));

	}
}