Spring Cloud Gateway 扩展支持多版本控制及灰度发布

第一反应，参考zuul 的实现，自定义断言，然后从上下中获取版本信息即可。但由于 spring cloud gateway 是基于webflux 的反应式编程，所以传统的TTL或者 RequestContextHolder 都不能正确的维护上下文请求。

先来看 spring clou的 gateway 默认的lb 策略实现 LoadBalancerClientFilter

public class LoadBalancerClientFilter implements GlobalFilter, Ordered {
    @Override
    public int getOrder() {
        return LOAD_BALANCER_CLIENT_FILTER_ORDER;
    }

    @Override
    @SuppressWarnings("Duplicates")
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        return chain.filter(exchange);
    }

    protected ServiceInstance choose(ServerWebExchange exchange) {
        return loadBalancer.choose(
                ((URI) exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR)).getHost());
    }
}

我们只需要重写 choose 方法，把上下文请求传递到路由断言中即可，如下

@Override
protected ServiceInstance choose(ServerWebExchange exchange) {
    HttpHeaders headers = exchange.getRequest().getHeaders();
    return loadBalancer.choose(((URI) exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR)).getHost(), headers);
}

然后在路由断言中通过 PredicateKey获取到即可

public abstract class AbstractDiscoveryEnabledPredicate extends AbstractServerPredicate {

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean apply(@Nullable PredicateKey input) {
        return input != null
                && input.getServer() instanceof NacosServer
                && apply((NacosServer) input.getServer(), (HttpHeaders) input.getLoadBalancerKey());
    }
}

最后根据版本来计算

    public class GrayMetadataAwarePredicate extends AbstractDiscoveryEnabledPredicate {

    @Override
    protected boolean apply(NacosServer server, HttpHeaders headers) {
        PigxRibbonRuleProperties ribbonProperties = SpringContextHolder.getBean(PigxRibbonRuleProperties.class);

        if (!ribbonProperties.isGrayEnabled()) {
            log.debug("gray closed,GrayMetadataAwarePredicate return true");
            return true;
        }

        final Map<String, String> metadata = server.getMetadata();
        String version = metadata.get(CommonConstants.VERSION);
        // 判断Nacos服务是否有版本标签
        if (StrUtil.isBlank(version)) {
            log.debug("nacos server tag is blank ,GrayMetadataAwarePredicate return true");
            return true;
        }

        // 判断请求中是否有版本
        String target = headers.getFirst(CommonConstants.VERSION);
        if (StrUtil.isBlank(target)) {
            log.debug("request headers version is blank,GrayMetadataAwarePredicate return true");
            return true;
        }

        log.debug("请求版本:{} ,当前服务版本:{}", target, version);
        return target.equals(version);
    }

}


参考：https://segmentfault.com/a/1190000019709733?utm_source=tag-newest