SpringCloud Zuul在何种情况下使用Hystrix及问题小结

Z时代
2024-01-10
分类：综合

首先，引入spring-cloud-starter-zuul之后会间接引入：

hystrix依赖已经引入，那么何种情况下使用hystrix呢？

在Zuul的自动配置类ZuulServerAutoConfiguration和ZuulProxyAutoConfiguration中总共会向Spring容器注入3个Zuul的RouteFilter，分别是

•SimpleHostRoutingFilter

简单路由，通过HttpClient向预定的URL发送请求
生效条件：
RequestContext.getCurrentContext().getRouteHost() != null
&& RequestContext.getCurrentContext().sendZuulResponse()
1、RequestContext中的routeHost不为空，routeHost就是URL，即使用URL直连
2、RequestContext中的sendZuulResponse为true，即是否将response发送给客户端，默认为true

•RibbonRoutingFilter

使用Ribbon、Hystrix和可插入的http客户端发送请求
生效条件：
(RequestContext.getRouteHost() == null && RequestContext.get(SERVICE_ID_KEY) != null
&& RequestContext.sendZuulResponse())
1、RequestContext中的routeHost为空，即URL为空
2、RequestContext中的serviceId不为空
3、RequestContext中的sendZuulResponse为true，即是否将response发送给客户端，默认为true

•SendForwardFilter

forward到本地URL
生效条件：
RequestContext.containsKey(FORWARD_TO_KEY)
&& !RequestContext.getBoolean(SEND_FORWARD_FILTER_RAN, false)
1、RequestContext中包含FORWARD_TO_KEY，即URL使用 forward: 映射
2、RequestContext中SEND_FORWARD_FILTER_RAN为false，SEND_FORWARD_FILTER_RAN意为“send forward是否运行过了”，在SendForwardFilter#run()时会ctx.set(SEND_FORWARD_FILTER_RAN, true)
综上所述，在使用serviceId映射的方法路由转发的时候，会使用Ribbon+Hystrix
而哪种路由配置方式是“URL映射”，哪种配置方式又是“serviceId映射”呢？
Zuul有一个前置过滤器PreDecorationFilter用于通过RouteLocator路由定位器决定在何时以何种方式路由转发
RouteLocator是用于通过请求地址匹配到Route路由的，之后PreDecorationFilter再通过Route信息设置RequestContext上下文，决定后续使用哪个RouteFilter做路由转发

所以就引出以下问题：

•什么是Route

•RouteLocator路由定位器如何根据请求路径匹配路由

•匹配到路由后，PreDecorationFilter如何设置RequestContext请求上下文

什么是Route

我总共见到两个和Route相关的类

ZuulProperties.ZuulRoute，用于和zuul配置文件关联，保存相关信息


org.springframework.cloud.netflix.zuul.filters.Route， RouteLocator找到的路由信息就是这个类，用于路由转发
public static class ZuulRoute {
 private String id; //ZuulRoute的id
 private String path; //路由的pattern，如 /foo/**
 private String serviceId; //要映射到此路由的服务id
 private String url; //要映射到路由的完整物理URL
 private boolean stripPrefix = true; //用于确定在转发之前是否应剥离此路由前缀的标志位
 private Boolean retryable; //此路由是否可以重试，通常重试需要serviceId和ribbon
 private Set<String> sensitiveHeaders = new LinkedHashSet(); //不会传递给下游请求的敏感标头列表
 private boolean customSensitiveHeaders = false; //是否自定义了敏感头列表
}
public class Route {
 private String id;
 private String fullPath;
 private String path;
 private String location; //可能是 url 或 serviceId
 private String prefix;
 private Boolean retryable;
 private Set<String> sensitiveHeaders = new LinkedHashSet<>();
 private boolean customSensitiveHeaders;
}

可以看到org.springframework.cloud.netflix.zuul.filters.Route和ZuulProperties.ZuulRoute基本一致，只是Route用于路由转发定位的属性location根据不同的情况，可能是一个具体的URL，可能是一个serviceId

RouteLocator路由定位器如何根据请求路径匹配路由

Zuul在自动配置加载时注入了2个RouteLocator

•CompositeRouteLocator：组合的RouteLocator，在getMatchingRoute()时会依次调用其它的RouteLocator，先找到先返回；CompositeRouteLocator的routeLocators集合中只有DiscoveryClientRouteLocator

•DiscoveryClientRouteLocator：可以将静态的、已配置的路由与来自DiscoveryClient服务发现的路由组合在一起，来自DiscoveryClient的路由优先；SimpleRouteLocator的子类（SimpleRouteLocator 基于加载到ZuulProperties中的配置定位Route路由信息）

其中CompositeRouteLocator是 @Primary 的，它是组合多个RouteLocator的Locator，其getMatchingRoute()方法会分别调用其它所有RouteLocator的getMatchingRoute()方法，通过请求路径匹配路由信息，只要匹配到了就马上返回

默认CompositeRouteLocator混合路由定位器的routeLocators只有一个DiscoveryClientRouteLocator，故只需分析DiscoveryClientRouteLocator#getMatchingRoute(path)


//----------DiscoveryClientRouteLocator是SimpleRouteLocator子类，其实是调用的SimpleRouteLocator##getMatchingRoute(path)
@Override
public Route getMatchingRoute(final String path) {
 return getSimpleMatchingRoute(path);
}
protected Route getSimpleMatchingRoute(final String path) {
 if (log.isDebugEnabled()) {
  log.debug("Finding route for path: " + path);
 }
 // routes是保存路由信息的map，如果此时还未加载，调用locateRoutes()
 if (this.routes.get() == null) {
  this.routes.set(locateRoutes());
 }
 if (log.isDebugEnabled()) {
  log.debug("servletPath=" + this.dispatcherServletPath);
  log.debug("zuulServletPath=" + this.zuulServletPath);
  log.debug("RequestUtils.isDispatcherServletRequest()="
    + RequestUtils.isDispatcherServletRequest());
  log.debug("RequestUtils.isZuulServletRequest()="
    + RequestUtils.isZuulServletRequest());
 }
 /**
  * 下面的方法主要是先对path做微调
  * 再根据path到routes中匹配到ZuulRoute
  * 最后根据 ZuulRoute 和 adjustedPath 生成 Route
  */
 String adjustedPath = adjustPath(path);
 ZuulRoute route = getZuulRoute(adjustedPath);
 return getRoute(route, adjustedPath);
}

下面我们来看看locateRoutes()是如何加载静态的、已配置的路由与来自DiscoveryClient服务发现的路由的


//----------DiscoveryClientRouteLocator#locateRoutes() 服务发现路由定位器的locateRoutes()
@Override
protected LinkedHashMap<String, ZuulRoute> locateRoutes() {
 //保存ZuulRoute的LinkedHashMap
 LinkedHashMap<String, ZuulRoute> routesMap = new LinkedHashMap<String, ZuulRoute>();
 //调用父类SimpleRouteLocator#locateRoutes()
 //加载ZuulProperties中的所有配置文件中的路由信息
 routesMap.putAll(super.locateRoutes());
 //如果服务发现客户端discovery存在
 if (this.discovery != null) {
  //将routesMap已经存在的配置文件中的ZuulRoute放入staticServices<serviceId, ZuulRoute>
  Map<String, ZuulRoute> staticServices = new LinkedHashMap<String, ZuulRoute>();
  for (ZuulRoute route : routesMap.values()) {
   String serviceId = route.getServiceId();
   //如果serviceId为null，以id作为serviceId，此情况适合 zuul.routes.xxxx=/xxxx/** 的情况
   if (serviceId == null) {
    serviceId = route.getId();
   }
   if (serviceId != null) {
    staticServices.put(serviceId, route);
   }
  }
  // Add routes for discovery services by default
  List<String> services = this.discovery.getServices(); //到注册中心找到所有service
  String[] ignored = this.properties.getIgnoredServices()
    .toArray(new String[0]);
  //遍历services
  for (String serviceId : services) {
   // Ignore specifically ignored services and those that were manually
   // configured
   String key = "/" + mapRouteToService(serviceId) + "/**";
   //如果注册中心的serviceId在staticServices集合中，并且此路由没有配置URL
   //那么，更新路由的location为serviceId
   if (staticServices.containsKey(serviceId)
     && staticServices.get(serviceId).getUrl() == null) {
    // Explicitly configured with no URL, cannot be ignored
    // all static routes are already in routesMap
    // Update location using serviceId if location is null
    ZuulRoute staticRoute = staticServices.get(serviceId);
    if (!StringUtils.hasText(staticRoute.getLocation())) {
     staticRoute.setLocation(serviceId);
    }
   }
   //如果注册中心的serviceId不在忽略范围内，且routesMap中还没有包含，添加到routesMap
   if (!PatternMatchUtils.simpleMatch(ignored, serviceId)
     && !routesMap.containsKey(key)) {
    // Not ignored
    routesMap.put(key, new ZuulRoute(key, serviceId));
   }
  }
 }
 // 如果routesMap中有 /** 的默认路由配置
 if (routesMap.get(DEFAULT_ROUTE) != null) {
  ZuulRoute defaultRoute = routesMap.get(DEFAULT_ROUTE);
  // Move the defaultServiceId to the end
  routesMap.remove(DEFAULT_ROUTE);
  routesMap.put(DEFAULT_ROUTE, defaultRoute);
 }
 //将routesMap中的数据微调后，放到values<String, ZuulRoute>，返回
 LinkedHashMap<String, ZuulRoute> values = new LinkedHashMap<>();
 for (Entry<String, ZuulRoute> entry : routesMap.entrySet()) {
  String path = entry.getKey();
  // Prepend with slash if not already present.
  if (!path.startsWith("/")) {
   path = "/" + path;
  }
  if (StringUtils.hasText(this.properties.getPrefix())) {
   path = this.properties.getPrefix() + path;
   if (!path.startsWith("/")) {
    path = "/" + path;
   }
  }
  values.put(path, entry.getValue());
 }
 return values;
}

此方法运行后就已经加载了配置文件中所有路由信息，以及注册中心中的服务路由信息，有的通过URL路由，有的通过serviceId路由

只需根据本次请求的requestURI与路由的pattern匹配找到对应的路由

匹配到路由后，PreDecorationFilter如何设置RequestContext请求上下文


//----------PreDecorationFilter前置过滤器
@Override
public Object run() {
 RequestContext ctx = RequestContext.getCurrentContext();
 final String requestURI = this.urlPathHelper.getPathWithinApplication(ctx.getRequest());
 Route route = this.routeLocator.getMatchingRoute(requestURI); //找到匹配的路由
 //----------------到上面为止是已经分析过的，根据requestURI找到匹配的Route信息
 // ==== 匹配到路由信息
 if (route != null) {
  String location = route.getLocation();
  if (location != null) {
   ctx.put(REQUEST_URI_KEY, route.getPath());//RequestContext设置 requestURI：路由的pattern路径
   ctx.put(PROXY_KEY, route.getId());//RequestContext设置 proxy：路由id
   //设置需要忽略的敏感头信息，要么用全局默认的，要么用路由自定义的
   if (!route.isCustomSensitiveHeaders()) {
    this.proxyRequestHelper
      .addIgnoredHeaders(this.properties.getSensitiveHeaders().toArray(new String[0]));
   }
   else {
    this.proxyRequestHelper.addIgnoredHeaders(route.getSensitiveHeaders().toArray(new String[0]));
   }
   //设置重试信息
   if (route.getRetryable() != null) {
    ctx.put(RETRYABLE_KEY, route.getRetryable());
   }
   //如果location是 http/https开头的，RequestContext设置 routeHost：URL
   //如果location是 forward:开头的，RequestContext设置 forward信息、routeHost：null
   //其它 RequestContext设置 serviceId、routeHost：null、X-Zuul-ServiceId
   if (location.startsWith(HTTP_SCHEME+":") || location.startsWith(HTTPS_SCHEME+":")) {
    ctx.setRouteHost(getUrl(location));
    ctx.addOriginResponseHeader(SERVICE_HEADER, location);
   }
   else if (location.startsWith(FORWARD_LOCATION_PREFIX)) {
    ctx.set(FORWARD_TO_KEY,
      StringUtils.cleanPath(location.substring(FORWARD_LOCATION_PREFIX.length()) + route.getPath()));
    ctx.setRouteHost(null);
    return null;
   }
   else {
    // set serviceId for use in filters.route.RibbonRequest
    ctx.set(SERVICE_ID_KEY, location);
    ctx.setRouteHost(null);
    ctx.addOriginResponseHeader(SERVICE_ID_HEADER, location);
   }
   //是否添加代理头信息 X-Forwarded-For
   if (this.properties.isAddProxyHeaders()) {
    addProxyHeaders(ctx, route);
    String xforwardedfor = ctx.getRequest().getHeader(X_FORWARDED_FOR_HEADER);
    String remoteAddr = ctx.getRequest().getRemoteAddr();
    if (xforwardedfor == null) {
     xforwardedfor = remoteAddr;
    }
    else if (!xforwardedfor.contains(remoteAddr)) { // Prevent duplicates
     xforwardedfor += ", " + remoteAddr;
    }
    ctx.addZuulRequestHeader(X_FORWARDED_FOR_HEADER, xforwardedfor);
   }
   //是否添加Host头信息
   if (this.properties.isAddHostHeader()) {
    ctx.addZuulRequestHeader(HttpHeaders.HOST, toHostHeader(ctx.getRequest()));
   }
  }
 }
 // ==== 没有匹配到路由信息
 else {
  log.warn("No route found for uri: " + requestURI);
  String fallBackUri = requestURI;
  String fallbackPrefix = this.dispatcherServletPath; // default fallback
               // servlet is
               // DispatcherServlet
  if (RequestUtils.isZuulServletRequest()) {
   // remove the Zuul servletPath from the requestUri
   log.debug("zuulServletPath=" + this.properties.getServletPath());
   fallBackUri = fallBackUri.replaceFirst(this.properties.getServletPath(), "");
   log.debug("Replaced Zuul servlet path:" + fallBackUri);
  }
  else {
   // remove the DispatcherServlet servletPath from the requestUri
   log.debug("dispatcherServletPath=" + this.dispatcherServletPath);
   fallBackUri = fallBackUri.replaceFirst(this.dispatcherServletPath, "");
   log.debug("Replaced DispatcherServlet servlet path:" + fallBackUri);
  }
  if (!fallBackUri.startsWith("/")) {
   fallBackUri = "/" + fallBackUri;
  }
  String forwardURI = fallbackPrefix + fallBackUri;
  forwardURI = forwardURI.replaceAll("//", "/");
  ctx.set(FORWARD_TO_KEY, forwardURI);
 }
 return null;
}