本文针对于测试环境SpringCloud Gateway问题解决。

1.背景介绍

本文遇到的问题都是在测试环境真正遇到的问题，不一定试用于所有人，仅做一次记录，便于遇到同样问题的干掉这些问题。

使用版本：SpringCloud 2.0.0.RELEASE

1.1 Gateway配置

之前系统是由阿里云SLB直接分发到几台生产服务器，但是经过研究，决定在中间加一层网关，也就是阿里云SLB分发流量到Gateway到下游服务。但是又由于种种原因，决定使用Host方式进行拦截处理，以下为部分配置代码：

spring:
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
      routes:
        - id: test_client
          uri: lb://TEST-CLIENT
          predicates:
            - Host=www.dalaoyang.cn
          order: 1
          filters:
            - DalaoyangAuth
            

注意，其中部分内容并非真实环境内容，但是场景绝对真实，如：

• test_client：routes的ID。
• uri：这里使用的Eureka内的application name
• Host：需要拦截的域名
• filters：域名前缀

1.2 Gateway过滤器

过滤器内容如下，稍后介绍：

@Component
public class DalaoyangAuthFilterFactory  extends AbstractGatewayFilterFactory<Object> {
    private static final Logger logger = LoggerFactory.getLogger(DalaoyangAuthFilterFactory.class);

    @Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            ServerHttpRequest host = exchange.getRequest().mutate().headers(httpHeaders -> {
                httpHeaders.remove("gate_way_auth");
                httpHeaders.add("gate_way_auth", "yes");
            }).build();
            //将现在的request 变成 change对象
            ServerWebExchange build = exchange.mutate().request(host).build();
            return chain.filter(build);
        };
    }
}

1.3 下游服务拦截器

下游服务拦截器大致内容如下，这段代码是原有的代码，这个功能大概就是加载公共的属性basePath，用于加载静态资源，比如前端的jquery.js，根据域名判断，然后选择是加载为http://127.0.0.1:8080/jquery.js还是https://www.dalaoyang.cn/jquery.js这种：

public class GlobalInterceptorAdapter extends HandlerInterceptorAdapter {

    private static Logger logger = LoggerFactory.getLogger(GlobalInterceptorAdapter.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws
            Exception {
        String scheme = request.getScheme();
        String serverName = request.getServerName();
        int port = request.getServerPort();
        String path = request.getContextPath();
        String basePath = "";
        if(serverName.indexOf("www.dalaoyang.cn")!=-1){
            basePath = "//" + serverName + path;
        }else {
            basePath = scheme + "://" + serverName + ":" + port + path;
        }
        if (logger.isDebugEnabled()) {
            logger.debug(basePath);
        }
        request.setAttribute("basePath", basePath);
        return true;
    }

}

1.4 下游服务用户过滤器

这段代码也是原有的代码，用户Session过滤器，这个完整内容很多，只截取遇到问题的片段，大致内容就是判断用户是否在其他地方登录，如果登录了就弹出的固定的提示页面，内容如下：

String url = null;
ApplicationConfig applicationConfig0 = getApplicationConfig();
if(applicationConfig0 != null) {
    String scheme = applicationConfig0.getUrlScheme();
    if(scheme != null) {
        String requestUrl = request.getRequestURL().toString();
            if(requestUrl != null && requestUrl.length() > 8) {
                requestUrl = requestUrl.substring(requestUrl.indexOf(":"), 
                                        requestUrl.indexOf("/", 8));
                url = scheme + requestUrl;
            }
    }
}
if(url != null) {
    response.sendRedirect(url + request.getContextPath() + "/session-time-out");
} else {
    response.sendRedirect(request.getContextPath() + "/session-time-out");
}

1.5 跳转流程

跳转如下：

1.域名指向了Gateway地址。
2.在浏览器使用域名访问Gateway，被Gateway转发到下游服务，返回对应响应。

2.问题一 下游服务无法获取域名

在使用上述配置后，使用request.getServerName()方法已经无法获取到域名了，经过测试，获取到的是服务器的ip地址，导致虽然页面可以正常跳转，但是无法获取到正确的域名，导致静态资源加载有问题。

在网上请教了很多人，本想看看是不是什么地方没有设置对，但是后台还是采取大多数人的建议，在header中加入一个域名信息，修改后Gateway过滤器如下：

@Component
public class DalaoyangAuthFilterFactory  extends AbstractGatewayFilterFactory<Object> {
    private static final Logger logger = LoggerFactory.getLogger(DalaoyangAuthFilterFactory.class);

    @Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            ServerHttpRequest host = exchange.getRequest().mutate().headers(httpHeaders -> {
                httpHeaders.remove("gate_way_auth");
                httpHeaders.add("gate_way_auth", "yes");
                
                httpHeaders.add("realServerName",
                exchange.getRequest().getURI().getHost());
                logger.info("headers:" + httpHeaders.toString());
            }).build();
            //将现在的request 变成 change对象
            ServerWebExchange build = exchange.mutate().request(host).build();
            return chain.filter(build);
        };
    }
}

很容易看到，就是如下这句话：

httpHeaders.add("realServerName",
              exchange.getRequest().getURI().getHost());

下游服务过滤修改为：

public class GlobalInterceptorAdapter extends HandlerInterceptorAdapter {
    private static Logger logger = LoggerFactory.getLogger(GlobalInterceptorAdapter.class);
    private final String TEST_SERVERNAME = "www.dalaoyang.cn";

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws
            Exception {
        String scheme = request.getScheme();
        String serverName = request.getServerName();
        String realServerName = request.getHeader("realServerName");
        int port = request.getServerPort();
        String path = request.getContextPath();
        String basePath = "";
        if((!StringUtils.isBlank(realServerName))){
            if(realServerName.contains(TEST_SERVERNAME)){
                basePath = "//" + realServerName + path;
            }
        }else {
            basePath = scheme + "://" + serverName + ":" + port + path;
        }
        if (logger.isDebugEnabled()) {
            logger.debug(basePath);
        }
        request.setAttribute("basePath", basePath);
        return true;
    }
}

其实大致内容就是，使用如下方式获取域名：

String realServerName = request.getHeader("realServerName");

到此，问题解决了，大部分内容跳转正常。

3.问题二 NPE异常

部分请求，经过路由访问报如下错误。

2018-06-20 01:26:04.254 ERROR 1 --- [reactor-http-client-epoll-11] .a.w.r.e.DefaultErrorWebExceptionHandler : Failed to handle request [DELETE http://localhost:8080/entity/5b29ad2cb3cb1f00010a1546]

java.lang.NullPointerException: null
        at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011) ~[na:1.8.0_111]
        at java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006) ~[na:1.8.0_111]
        at org.springframework.cloud.gateway.filter.NettyRoutingFilter.lambda$filter$3(NettyRoutingFilter.java:117) ~[spring-cloud-gateway-core-2.0.0.RELEASE.jar!/:2.0.0.RELEASE]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:177) ~[reactor-core-3.1.8.RELEASE.jar!/:3.1.8.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:108) ~[reactor-core-3.1.8.RELEASE.jar!/:3.1.8.RELEASE]
        at reactor.core.publisher.FluxRetryPredicate$RetryPredicateSubscriber.onNext(FluxRetryPredicate.java:81) ~[reactor-core-3.1.8.RELEASE.jar!/:3.1.8.RELEASE]
        at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:146) ~[reactor-core-3.1.8.RELEASE.jar!/:3.1.8.RELEASE]
        at reactor.ipc.netty.channel.PooledClientContextHandler.fireContextActive(PooledClientContextHandler.java:85) ~[reactor-netty-0.7.8.RELEASE.jar!/:0.7.8.RELEASE]
        at reactor.ipc.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:578) ~[reactor-netty-0.7.8.RELEASE.jar!/:0.7.8.RELEASE]
        at reactor.ipc.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:136) ~[reactor-netty-0.7.8.RELEASE.jar!/:0.7.8.RELEASE]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310) ~[netty-codec-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:284) ~[netty-codec-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965) ~[netty-transport-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:808) ~[netty-transport-native-epoll-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:408) ~[netty-transport-native-epoll-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:308) ~[netty-transport-native-epoll-4.1.25.Final.jar!/:4.1.25.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) ~[netty-common-4.1.25.Final.jar!/:4.1.25.Final]
        at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_111]

遇到问题后，没有很慌，打开了百度查了查（微笑）。百度没让我很失望，基本上没啥答复，然后谷歌了一下，看到了github上的一个issues，大致内容感觉是SpringCloud Gateway 2.0.0.RELEASE版本有些问题，升级一下版本就好了，如图。

Github issues地址：

https://github.com/spring-cloud/spring-cloud-gateway/issues/429
https://github.com/spring-cloud/spring-cloud-gateway/issues/374

说实话，感觉是版本问题，但是又看到了一篇国人的文章，地址是：http://xiaoqiangge.com/aritcle/1545889008833.html，问题大致类似，加了一下博主的微信，请教了一下，大致了解到了，升级了一下版本，问题解决。

感谢小强哥！！！

4.问题三 下游用户过滤器跳转失效

问题是这样的，刚刚介绍了，用户在其他地方登录会自动跳转至一个界面提示给用户，发现问题是无法跳转。

查看gateway日志，大概提示了这样一句话，如下：

Unhandled failure: Connection has been closed, response already set (status=302)

从内容大致可以看出，重定向有问题，想到了在用户过滤器中最后的重定向，决定在这里下手，修改后内容如下：

String scheme = request.getScheme();
String serverName = request.getServerName();
String realServerName = request.getHeader("realServerName");
int port = request.getServerPort();
String path = request.getContextPath();
String basePath = "";
if((!StringUtils.isEmpty(realServerName))){
        if(realServerName.contains(TEST_SERVERNAME)){
        basePath = "https://" + realServerName + path;
    }else {
        basePath = scheme + "://" + serverName + ":" + port + path;
    }
response.sendRedirect(basePath + "/session-time-out");

问题也解决了，目前还在踩坑测试中，如果大家有类似经验可以一起探讨。