目录
为路由提供HystrixFallback
当Zuul中某一个路由的断路器被断开时,你可以通过创建一个FallbackProvider类型的Bean来为它提供一个Fallback响应。在这个Bean中你需要指定Fallback响应所对应的路由的ID并提供一个ClientHttpResponse作为返回的Fallback响应,下面是一个FallbackProvider实现的实例。
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;
import com.netflix.hystrix.exception.HystrixTimeoutException;
@Component
public class MessageFallbackProvider implements FallbackProvider {
@Override
public String getRoute() {
return "zuul-msg";
}
@Override
public ClientHttpResponse fallbackResponse(String route, final Throwable cause) {
if (cause instanceof HystrixTimeoutException) {
return response(HttpStatus.GATEWAY_TIMEOUT);
} else {
return response(HttpStatus.INTERNAL_SERVER_ERROR);
}
}
private ClientHttpResponse response(final HttpStatus status) {
return new ClientHttpResponse() {
@Override
public HttpStatus getStatusCode() throws IOException {
return status;
}
@Override
public int getRawStatusCode() throws IOException {
return status.value();
}
@Override
public String getStatusText() throws IOException {
return status.getReasonPhrase();
}
@Override
public void close() {
}
@Override
public InputStream getBody() throws IOException {
return new ByteArrayInputStream("消息服务暂时不可用,请稍后重试!".getBytes());
}
@Override
public HttpHeaders getHeaders() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
return headers;
}
};
}
}
路由的配置信息如下:
zuul:
routes:
message-service: /zuul-msg/**
当message-service服务调用失败时,返回结果见下图。
如果你想为所有的路由提供一个默认的Fallback,可以创建一个FallbackProvider Bean并将它的getRoute() 方法的返回值设置为 “*”或者 null。
class MyFallbackProvider implements FallbackProvider {
@Override
public String getRoute() {
return "*";
}
@Override
public ClientHttpResponse fallbackResponse(String route, Throwable throwable) {
return new ClientHttpResponse() {
@Override
public HttpStatus getStatusCode() throws IOException {
return HttpStatus.OK;
}
@Override
public int getRawStatusCode() throws IOException {
return 200;
}
@Override
public String getStatusText() throws IOException {
return "OK";
}
@Override
public void close() {
}
@Override
public InputStream getBody() throws IOException {
return new ByteArrayInputStream("fallback".getBytes());
}
@Override
public HttpHeaders getHeaders() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
return headers;
}
};
}
}
重写Location头信息
如果Zuul面向的是一个Web应用,那么你可能会碰到需要重写Location请求头的情况,你只需要创建一个LocationRewriteFilter类型Bean即可。
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
import org.springframework.cloud.netflix.zuul.filters.post.LocationRewriteFilter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableZuulProxy
public class ZuulConfig {
@Bean
public LocationRewriteFilter locationRewriteFilter() {
return new LocationRewriteFilter();
}
}
注意:此过滤器会作用于所有响应状态码为 3XX 的Location头信息,这并不一定适用于所有的场景,比如重定向到外部URL。
启用跨域请求
默认情况下,Zuul会把所有的Cross Origin requests (CORS,跨域请求)路由给相应的服务,如果你想代替Zuul自己来处理这些请求,你可以提供一个自定义的 WebMvcConfigurer Bean:
@Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurer() {
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/path-1/**").allowedOrigins("http://allowed-origin.com").allowedMethods("GET",
"POST");
}
};
}
在这个例子中,我们允许从 http://allowed-origin.com 向Zuul中以 path-1 开头的终端发送 GET和POST类型的跨域请求。你既可以将 CORS 配置作用于指定的路径,也可以使用 /** 让它作用于整个应用。你可以在其中配置以下属性:allowedOrigins、allowedMethods、allowedHeaders、exposedHeaders、allowCredentials、maxAge。
创建前置过滤器
前置过滤器对RequestContext中的数据进行设置,并提供给下游的过滤器使用,它的最主要的用途就是对路由过滤器所需的信息进行设置。
import javax.servlet.http.HttpServletRequest;
import org.springframework.cloud.netflix.zuul.filters.support.FilterConstants;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
public class QueryParamPreFilter extends ZuulFilter {
@Override
public int filterOrder() {
return FilterConstants.PRE_DECORATION_FILTER_ORDER - 1; // run before PreDecoration
}
@Override
public String filterType() {
return FilterConstants.PRE_TYPE;
}
@Override
public boolean shouldFilter() {
RequestContext ctx = RequestContext.getCurrentContext();
return !ctx.containsKey(FilterConstants.FORWARD_TO_KEY) // a filter has already forwarded
&& !ctx.containsKey(FilterConstants.SERVICE_ID_KEY); // a filter has already determined serviceId
}
@Override
public Object run() {
RequestContext ctx = RequestContext.getCurrentContext();
HttpServletRequest request = ctx.getRequest();
if (request.getParameter("sample") != null) {
// put the serviceId in `RequestContext`
ctx.put(FilterConstants.SERVICE_ID_KEY, request.getParameter("foo"));
}
return null;
}
}
创建路由过滤器
路由过滤器在前置过滤器之后运行,并负责构造需要发送给其他服务的请求。它在这的主要工作是:把请求数据传送至客户端所需要的 model 中,并把客户端 model 中的内容转换成响应数据返回。
import java.io.InputStream;
import java.util.Enumeration;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.netflix.zuul.filters.ProxyRequestHelper;
import org.springframework.cloud.netflix.zuul.filters.support.FilterConstants;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.StreamUtils;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import okhttp3.Headers;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import okhttp3.internal.http.HttpMethod;
public class OkHttpRoutingFilter extends ZuulFilter {
@Autowired
private ProxyRequestHelper helper;
@Override
public String filterType() {
return FilterConstants.ROUTE_TYPE;
}
@Override
public int filterOrder() {
return FilterConstants.SIMPLE_HOST_ROUTING_FILTER_ORDER - 1;
}
@Override
public boolean shouldFilter() {
return RequestContext.getCurrentContext().getRouteHost() != null
&& RequestContext.getCurrentContext().sendZuulResponse();
}
@Override
public Object run() {
OkHttpClient httpClient = new OkHttpClient.Builder().build(); // customize
RequestContext context = RequestContext.getCurrentContext();
HttpServletRequest request = context.getRequest();
String method = request.getMethod();
String uri = this.helper.buildZuulRequestURI(request);
Headers.Builder headers = new Headers.Builder();
Enumeration<String> headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
String name = headerNames.nextElement();
Enumeration<String> values = request.getHeaders(name);
while (values.hasMoreElements()) {
String value = values.nextElement();
headers.add(name, value);
}
}
try {
InputStream inputStream = request.getInputStream();
RequestBody requestBody = null;
if (inputStream != null && HttpMethod.permitsRequestBody(method)) {
MediaType mediaType = null;
if (headers.get("Content-Type") != null) {
mediaType = MediaType.parse(headers.get("Content-Type"));
}
requestBody = RequestBody.create(mediaType, StreamUtils.copyToByteArray(inputStream));
}
Request.Builder builder = new Request.Builder().headers(headers.build()).url(uri).method(method,
requestBody);
Response response = httpClient.newCall(builder.build()).execute();
LinkedMultiValueMap<String, String> responseHeaders = new LinkedMultiValueMap<>();
for (Map.Entry<String, List<String>> entry : response.headers().toMultimap().entrySet()) {
responseHeaders.put(entry.getKey(), entry.getValue());
}
this.helper.setResponse(response.code(), response.body().byteStream(), responseHeaders);
context.setRouteHost(null); // prevent SimpleHostRoutingFilter from running
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
创建后置过滤器
后置过滤器通常是用来对响应进行处理,例如下面这个过滤器添加了一个UUID作为 X-Sample 的头内容。
import java.util.UUID;
import javax.servlet.http.HttpServletResponse;
import org.springframework.cloud.netflix.zuul.filters.support.FilterConstants;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
public class AddResponseHeaderFilter extends ZuulFilter {
@Override
public String filterType() {
return FilterConstants.POST_TYPE;
}
@Override
public int filterOrder() {
return FilterConstants.SEND_RESPONSE_FILTER_ORDER - 1;
}
@Override
public boolean shouldFilter() {
return true;
}
@Override
public Object run() {
RequestContext context = RequestContext.getCurrentContext();
HttpServletResponse servletResponse = context.getResponse();
servletResponse.addHeader("X-Sample", UUID.randomUUID().toString());
return null;
}
}
Zuul错误处理
在Zuul过滤器生命周期的任一阶段一旦出现异常,错误过滤器就会执行。SendErrorFilter 只会在RequestContext.getThrowable() 不是 null 的时候运行。它会在请求中设置一些特定的 javax.servlet.error.* 属性并将请求转向Springboot的错误页面。
应用上下文饿加载
Zuul 在内部使用的是Ribbon 对远程url进行调用。默认情况下,Ribbon客户端会在Spring Cloud第一次调用时进行懒加载。如果需要在应用启动时就进行加载,可以做如下配置。
zuul:
ribbon:
eager-load:
enabled: true
请求失败重试
Spring Cloud Netflix 提供了很多种方法用来创建 HTTP 请求,你可以使用负载均衡的RestTemplate、Ribbon 或者 Feign ,但无论你选择了哪一种,都有可能会出现请求失败的情况。当一个请求失败时,你可能会希望它自动地进行重试,要实现这一点的话,你需要把 Spring Retry 添加到你的classpath ,然后,负载均衡的RestTemplate、Ribbon 、 Feign 以及 Zuul 就会对所有失败的请求自动进行重试(前提是你的配置允许它这样做的话)。
补偿策略
默认情况下,重试请求是没有补偿策略的,如果你想要配置一个补偿策略,你需要为指定的服务创建一个 LoadBalancedRetryFactory 类型的Bean,并重写它的 createBackOffPolicy 方法。
@Configuration
public class MyConfiguration {
@Bean
LoadBalancedRetryFactory retryFactory() {
return new LoadBalancedRetryFactory() {
@Override
public BackOffPolicy createBackOffPolicy(String service) {
return new ExponentialBackOffPolicy();
}
};
}
}
相关配置
在使用Ribbon进行重试时,你可以使用下面前三个个Ribbon配置项对重试的功能进行控制。
# Max number of retries on the same server (excluding the first try)
sample-client.ribbon.MaxAutoRetries=1
# Max number of next servers to retry (excluding the first server)
sample-client.ribbon.MaxAutoRetriesNextServer=1
# Whether all operations can be retried for this client
sample-client.ribbon.OkToRetryOnAllOperations=true
# Interval to refresh the server list from the source
sample-client.ribbon.ServerListRefreshInterval=2000
# Connect timeout used by Apache HttpClient
sample-client.ribbon.ConnectTimeout=3000
# Read timeout used by Apache HttpClient
sample-client.ribbon.ReadTimeout=3000
# Initial list of servers, can be changed via Archaius dynamic property at runtime
sample-client.ribbon.listOfServers=www.microsoft.com:80,www.yahoo.com:80,www.google.com:80
另外,如果你想当返回的响应的状态码为某些值的时候才进行重试,你可以使用 clientName.ribbon.retryableStatusCodes 把那些需要Ribbon客户端进行重试的状态码列举出来。
clientName:
ribbon:
retryableStatusCodes: 404,502
或者创建一个 LoadBalancedRetryPolicy 类型的Bean ,并实现它的retryableStatusCode方法。
禁用重试
# 全部禁用
zuul.retryable=false
# 禁用指定路由
zuul.routes.routename.retryable=false
参考文章
https://github.com/spring-projects/spring-retry
https://cloud.spring.io/spring-cloud-netflix/single/spring-cloud-netflix.html#netflix-zuul-starter