Spring Cloud Gateway运行时动态配置网关

Spring Cloud Gateway官方教程讲的都是提早在配置文件中配置网关，实际项目中，Spring Cloud Gateway做为微服务的入口，须要尽可能避免重启，因此咱们须要在Spring Cloud Gateway运行时动态配置网关。

Spring Cloud Gateway自带接口

Spring Cloud Gateway在2018年6月份发布了2.0第一个release版本，官方文档并无讲如何动态配置，翻看Spring Cloud Gateway源码，发现类org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint中提供了网关配置Restful接口，默认没有启用。在类org.springframework.cloud.gateway.config.GatewayAutoConfiguration中配置了GatewayControllerEndpoint

@Configuration
@ConditionalOnClass(Health.class)
protected static class GatewayActuatorConfiguration {

    @Bean
    @ConditionalOnEnabledEndpoint
    public GatewayControllerEndpoint gatewayControllerEndpoint(RouteDefinitionLocator routeDefinitionLocator, List<GlobalFilter> globalFilters,
                                                            List<GatewayFilterFactory> GatewayFilters, RouteDefinitionWriter routeDefinitionWriter,
                                                            RouteLocator routeLocator) {
        return new GatewayControllerEndpoint(routeDefinitionLocator, globalFilters, GatewayFilters, routeDefinitionWriter, routeLocator);
    }
}

存在org.springframework.boot.actuate.health.Health时启用，添加actuator依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

在gateway项目的application.yml中启用gateway api：

#开启actuator管理api，后面要关闭
management:
  endpoints:
    web:
      exposure:
        include: "*"

访问 http://localhost:网关端口/actuator/gateway/routes，返回了当前网关的路由信息。

编码方式

不过这里咱们不打算用自带的Restful接口，一来官方文档也没说新增网关参数怎么传，再者咱们也不但愿在网关暴露这些接口。参照org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint，咱们本身编程来动态改变网关。

直接上代码：

import java.net.URI;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.gateway.event.RefreshRoutesEvent;
import org.springframework.cloud.gateway.handler.predicate.PredicateDefinition;
import org.springframework.cloud.gateway.route.RouteDefinition;
import org.springframework.cloud.gateway.route.RouteDefinitionWriter;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Service;
import org.springframework.web.util.UriComponentsBuilder;

import reactor.core.publisher.Mono;

@Service
public class TestGatewayService implements ApplicationEventPublisherAware {

    @Autowired
    private RouteDefinitionWriter     routeDefinitionWriter;
    private ApplicationEventPublisher publisher;

    public String save() {
        RouteDefinition definition = new RouteDefinition();
        PredicateDefinition predicate = new PredicateDefinition();
        Map<String, String> predicateParams = new HashMap<>(8);

        definition.setId("baiduRoute");
        predicate.setName("Path");
        //请替换成本地可访问的路径
        predicateParams.put("pattern", "/baidu");
        //请替换成本地可访问的路径
        predicateParams.put("pathPattern", "/baidu");
        predicate.setArgs(predicateParams);
        definition.setPredicates(Arrays.asList(predicate));
        //请替换成本地可访问的域名
        URI uri = UriComponentsBuilder.fromHttpUrl("http://www.baidu.com").build().toUri();
        definition.setUri(uri);
        routeDefinitionWriter.save(Mono.just(definition)).subscribe();
        this.publisher.publishEvent(new RefreshRoutesEvent(this));
        return "success";
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.publisher = applicationEventPublisher;
    }
}

代码说明：

一、predicate.setName("Path"); 设置predicat名称，这个名称不是乱起的，Spring会根据名称去查找对应的FilterFactory，目前支持的名称有：After、Before、Between、Cookie、Header、Host、Method、Path、Query、RemoteAddr。

对应官方文档的Route Predicate Factories（http://cloud.spring.io/spring-cloud-static/spring-cloud-gateway/2.0.0.RELEASE/single/spring-cloud-gateway.html）

二、definition.setId("baiduRoute");  设置definition的id，须要全局惟一，默认使用UUID。

三、predicateParams.put("pattern", "/baidu");  每一个Route Predicate的参数不一样，详情在官网文档查看对应的Route Predicate配置示例，然而官方文档也很坑，好比Path Route的- Path=/foo/{segment}，把参数给省略了。仍是得看源码，在包org.springframework.cloud.gateway.handler.predicate里有Spring Cloud Gateway全部的Predicate，打开对应的RoutePredicateFactory，内部类Config就是该Predicate支持的参数。

四、routeDefinitionWriter.save(Mono.just(definition)).subscribe(); 默认的RouteDefinitionWriter实现类是org.springframework.cloud.gateway.route.InMemoryRouteDefinitionRepository。注意最后必定要调用subscribe()，不然不执行。

至此已编码动态配置了一个基本的网关。

带Filter的配置代码：

RouteDefinition routeDefinition = new RouteDefinition();
PredicateDefinition predicateDefinition = new PredicateDefinition();
Map<String, String> predicateParams = new HashMap<>(8);
Map<String, String> filterParams = new HashMap<>(8);
FilterDefinition filterDefinition = new FilterDefinition();
URI uri = UriComponentsBuilder.fromUriString("lb://HELLO-SERVICE").build().toUri();

routeDefinition.setId("rateLimitTest");
// 名称是固定的，spring gateway会根据名称找对应的PredicateFactory
predicateDefinition.setName("Path");
predicateParams.put("pattern", "/rate/**");
predicateDefinition.setArgs(predicateParams);

// 名称是固定的，spring gateway会根据名称找对应的FilterFactory
filterDefinition.setName("RequestRateLimiter");
// 每秒最大访问次数
filterParams.put("redis-rate-limiter.replenishRate", "2");
// 令牌桶最大容量
filterParams.put("redis-rate-limiter.burstCapacity", "3");
// 限流策略(#{@BeanName})
filterParams.put("key-resolver", "#{@hostAddressKeyResolver}");
// 自定义限流器(#{@BeanName})
//filterParams.put("rate-limiter", "#{@redisRateLimiter}");
filterDefinition.setArgs(filterParams);

routeDefinition.setPredicates(Arrays.asList(predicateDefinition));
routeDefinition.setFilters(Arrays.asList(filterDefinition));
routeDefinition.setUri(uri);
routeDefinitionWriter.save(Mono.just(routeDefinition)).subscribe();
publisher.publishEvent(new RefreshRoutesEvent(this));

须要注意的是filterParams.put("key-resolver", "#{@hostAddressKeyResolver}"); hostAddressKeyResolver是我自定义的Spring Bean，#{@BeanName}是Spring的表达式，用来注入Bean。

自定义RouteDefinitionWriter

Spring Cloud Gateway默认的RouteDefinitionWriter实现类是org.springframework.cloud.gateway.route.InMemoryRouteDefinitionRepository，Route信息保存在当前实例的内存中，这在集群环境中会存在同步问题。咱们能够自定义一个基于Redis的RouteDefinitionWriter。

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.gateway.route.RouteDefinition;
import org.springframework.cloud.gateway.route.RouteDefinitionRepository;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import com.alibaba.fastjson.JSON;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

/**
 * 使用Redis保存自定义路由配置（代替默认的InMemoryRouteDefinitionRepository）
 * <p/>
 * 存在问题：每次请求都会调用getRouteDefinitions，当网关较多时，会影响请求速度，考虑放到本地Map中，使用消息通知Map更新。
 *
 * @since 2018年7月9日 下午2:39:02
 */
@Component
public class RedisRouteDefinitionRepository implements RouteDefinitionRepository {

    public static final String  GATEWAY_ROUTES = "geteway_routes";
    @Autowired
    private StringRedisTemplate redisTemplate;

    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        List<RouteDefinition> routeDefinitions = new ArrayList<>();
        redisTemplate.opsForHash().values(GATEWAY_ROUTES).stream().forEach(routeDefinition -> {
            routeDefinitions.add(JSON.parseObject(routeDefinition.toString(), RouteDefinition.class));
        });
        return Flux.fromIterable(routeDefinitions);
    }

    @Override
    public Mono<Void> save(Mono<RouteDefinition> route) {
        return route
                .flatMap(routeDefinition -> {
                    redisTemplate.opsForHash().put(GATEWAY_ROUTES, routeDefinition.getId(),
                            JSON.toJSONString(routeDefinition));
                    return Mono.empty();
                });
    }

    @Override
    public Mono<Void> delete(Mono<String> routeId) {
        return routeId.flatMap(id -> {
            if (redisTemplate.opsForHash().hasKey(GATEWAY_ROUTES, id)) {
                redisTemplate.opsForHash().delete(GATEWAY_ROUTES, id);
                return Mono.empty();
            }
            return Mono.defer(() -> Mono.error(new NotFoundException("RouteDefinition not found: " + routeId)));
        });
    }

}