如果你也在做SpringCloudGateway网关开发，希望这篇文章能给你带来一些启发 。

背景

先说背景，某油项目，通过SpringCloudGateway配置了1.6万个路由规则，实际接口调用过程中，会偶现部分接口从发起请求到业务应用处理间隔了大概5秒的时间，经排查后发现是SpringCloudGateway底层在查找对应的Route时采用了遍历+断言匹配的方式，路由规则太多时就会出现耗时太久的问题，对应的源码如下:

protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
	return this.routeLocator
			.getRoutes()
			//individually filter routes so that filterWhen error delaying is not a problem
			.concatMap(route -> Mono
					.just(route)
					.filterWhen(r -> {
						// add the current route we are testing
						exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, r.getId());
						return r.getPredicate().apply(exchange);
					})
					//instead of immediately stopping main flux due to error, log and swallow it
					.doOnError(e -> logger.error("Error applying predicate for route: "+route.getId(), e))
					.onErrorResume(e -> Mono.empty())
			)
			// .defaultIfEmpty() put a static Route not found
			// or .switchIfEmpty()
			// .switchIfEmpty(Mono.<Route>empty().log("noroute"))
			.next()
			//TODO: error handling
			.map(route -> {
				if (logger.isDebugEnabled()) {
					logger.debug("Route matched: " + route.getId());
				}
				validateRoute(route, exchange);
				return route;
			});

	/* TODO: trace logging
		if (logger.isTraceEnabled()) {
			logger.trace("RouteDefinition did not match: " + routeDefinition.getId());
		}*/
}

目标

找到了问题，就需要对这块路由查找的代码进行优化，我们分析了下路由规则，发现可以用请求方法Method+请求路径Path作为key，把对应的Route作为缓存值，通过ServerWebExchange直接命中对应的路由对象（这里要注意下，如果有同样的问题，需要根据实际情况设计缓存键，比如/person/**这种断言Path就不适用了），对应的路由规则如下:

{
    "predicates": [
        {
            "args": {
                "_genkey_0": "/v1/structuredData/serviceData/cestc_dportal/MH_GX_JS_SJCZQX3080"
            },
            "name": "Path"
        },
        {
            "args": {
                "_genkey_0": "GET"
            },
            "name": "Method"
        }
    ],
    "filters": [
        {
            "args": {
                "_genkey_1": "/myapi/v1.0/zhyApi/getDataForGet",
                "_genkey_0": "/v1/structuredData/serviceData/cestc_dportal/MH_GX_JS_SJCZQX3080"
            },
            "name": "RewritePath"
        }
    ],
    "id": "02024012311262643900000101579677",
    "uri": "lb://myapi",
    "order": 0
}

定义路由缓存策略

接口定义 。

/**
 * 路由断言缓存实现
 * 通过ServerWebExchange快速查找Route
 * @author changxy
 */
public interface RoutePredicateCacheable {

    /**
     * 更新缓存路由
     * @param routeDefinition
     */
    void update(List<RouteDefinition> routeDefinition);

    /**
     * 根据请求上下文匹配对应路由
     * @param exchange
     * @return
     */
    Optional<Route> getRoute(ServerWebExchange exchange);

    static RoutePredicateCacheable empty() {
        return new BlankRoutePredicateCacheable();
    }

}

使用本地内存存放路由缓存 。

/**
 * 本地内存Route对象缓存器
 * RouteDefinitionRouteLocator类中处理RouteDefinition到Route的转换
 * @author changxy
 */
public class InMemoryRoutePredicateCacheable implements RoutePredicateCacheable {

    private final RouteDefinitionRouteLocator routeLocator;

    private final Map<String, Route> routes = new ConcurrentHashMap<>(1024);

    protected final static String CACHE_KEY_FORMAT = "%s:%s";

    public InMemoryRoutePredicateCacheable(RouteDefinitionRouteLocator routeLocator) {
        this.routeLocator = routeLocator;
    }

    @Override
    public void update(List<RouteDefinition> routeDefinitions) {
        if (CollectionUtils.isEmpty(routeDefinitions)) {
            return ;
        }

        // 清空缓存
        routes.clear();

        Map<String, Route> routeMap = this.routeLocator
                .getRoutes()
                .toStream()
                .collect(Collectors.toMap(Route::getId, r -> r));

        for (RouteDefinition routeDefinition : routeDefinitions) {
            routes.put(key(routeDefinition), routeMap.get(routeDefinition.getId()));
        }

        System.out.println(1);

    }

    @Override
    public Optional<Route> getRoute(ServerWebExchange exchange) {
        return Optional.ofNullable(routes.get(key(exchange)));
    }

    public Optional<Route> lookupRoute(String routeId) {
        return this.routeLocator
                .getRoutes()
                .toStream()
                .filter(route -> Objects.equals(route.getId(), routeId))
                .findFirst();
    }

    /**
     * 根据路由定义生成key
     * @param routeDefinition
     * @return
     */
    protected String key(RouteDefinition routeDefinition) {
        Map<String, String> routeDefinitionParams = routeDefinition.getPredicates()
                .stream()
                .collect(
                        Collectors.toMap(
                                PredicateDefinition::getName,
                                p -> p.getArgs().get("_genkey_0"),
                                (k1, k2) -> k2
                        )
                );
        if (null != routeDefinitionParams
                && routeDefinitionParams.containsKey("Method")
                && routeDefinitionParams.containsKey("Path")) {
            return String.format(CACHE_KEY_FORMAT, routeDefinitionParams.get("Method"), routeDefinitionParams.get("Path"));
        }
        return StringUtils.EMPTY;
    }

    /**
     * 根据请求对象生成key
     * @param exchange
     * @return
     */
    protected String key(ServerWebExchange exchange) {
        String method = exchange.getRequest().getMethodValue();
        String paths = exchange.getRequest().getPath().value();
        return String.format(CACHE_KEY_FORMAT, method, paths);
    }

}

我们的路由规则存放在Nacos配置中心，网关服务启动时、Nacos配置发生变更时，同步刷新路由缓存，这块可以根据实际情况定义缓存更新策略，部分伪代码如下:

List<RouteDefinition> routeDefinitions = list.stream().map(DynamicRoutingConfig.this::assembleRouteDefinition).collect(Collectors.toList());

// 20240124 更新Route缓存，优化路由匹配速度
routePredicateCacheable.update(routeDefinitions);

重写RoutePredicateHandlerMapping

public class CachingRoutePredicateHandlerMapping extends RoutePredicateHandlerMapping {

    private final RoutePredicateCacheable routePredicateCacheable;

    public CachingRoutePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator, GlobalCorsProperties globalCorsProperties, Environment environment, RoutePredicateCacheable routePredicateCacheable) {
        super(webHandler, routeLocator, globalCorsProperties, environment);
        this.routePredicateCacheable = routePredicateCacheable;
    }

    @Override
    protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
        Optional<Route> route = routePredicateCacheable.getRoute(exchange);
        if (route.isPresent()) {
            return Mono.just(route.get());
        } else {
            return super.lookupRoute(exchange);
        }
    }

}

定义AutoConfiguration

@Configuration
@ConditionalOnProperty(name = "route.cache.enabled", matchIfMissing = false)
@AutoConfigureBefore(GatewayAutoConfiguration.class)
public class FastRoutePredicateHandlerAutoConfiguration {

    @Bean
    @ConditionalOnMissingBean
    public RoutePredicateCacheable routePredicateCacheable(RouteDefinitionRouteLocator routeLocator) {
        return new InMemoryRoutePredicateCacheable(routeLocator);
    }

    @Bean("cachingRoutePredicateHandlerMapping")
    public RoutePredicateHandlerMapping routePredicateHandlerMapping(
            FilteringWebHandler webHandler, RouteLocator routeLocator,
            GlobalCorsProperties globalCorsProperties, Environment environment, RoutePredicateCacheable routePredicateCacheable) {
        return new CachingRoutePredicateHandlerMapping(webHandler, routeLocator,
                globalCorsProperties, environment, routePredicateCacheable);
    }

}

不加载SpringCloudGateway自己的RoutePredicateHandlerMapping

@Configuration
@ConditionalOnProperty(name = "route.cache.enabled", matchIfMissing = false)
public class RoutePredicateBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        registry.removeBeanDefinition("routePredicateHandlerMapping");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

    }
}

优化效果测试

毫秒级响应了 。

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