需求
最近小编的项目中出现了很多feign 调用出现 Read Time out 的异常，但因为没有集成链路追踪的第三方框架，查不到原因。
所以想到打印请求的ip地址，判断是指定的服务器出现的问题还是所有服务器都有这个问题，但是feign 打印异常日志不会显示目的端地址，这就很难受了没办法只能自己改装下
大致想法
需要改装肯定需要知道feign 具体请求调用的源码，大致需要知道下面几个问题
- feign 集成了ribbon 如何在负载均衡之后获取真实的ip地址
- feign 实际请求 http 源码在哪
- 能否替换 feign http 请求的组件
源码解析
之前小编有两篇文章分析过 feign相关的源码
自定义 feign 调用实现 hystrix 超时、异常熔断
Feign 集成 Hystrix实现不同的调用接口不同的设置
这其中有个关键的源码位置在于 InvocationHandler 的 invoke 方法，在feign 组件中大致有两个类实现了此接口
FeignInvocationHandler HystrixInvocationHandler
如果 项目中使用了 Hystrix 那么会用到HystrixInvocationHandler那个，否则一般是FeignInvocationHandler（自定义组件的除外）
那么此时只需要在invoke 方法中打个断点就行
此时跟踪到
feign.SynchronousMethodHandler#executeAndDecode
Object executeAndDecode(RequestTemplate template) throws Throwable {
Request request = targetRequest(template);
.......
Response response;
long start = System.nanoTime();
try {
// 真正执行请求
response = client.execute(request, options);
response.toBuilder().request(request).build();
} catch (IOException e) {
....
throw errorExecuting(request, e);
}
.....
}
通过debug就知道这个 client 是
LoadBalancerFeignClient org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient#execute
public Response execute(Request request, Request.Options options) throws IOException {
try {
URI asUri = URI.create(request.url());
String clientName = asUri.getHost();
URI uriWithoutHost = cleanUrl(request.url(), clientName);
// 封装 ribbon 请求组件
FeignLoadBalancer.RibbonRequest ribbonRequest = new FeignLoadBalancer.RibbonRequest(
this.delegate, request, uriWithoutHost);
IClientConfig requestConfig = getClientConfig(options, clientName);
// 这行是关键
return
// 获取 FeignLoadBalancer
lbClient(clientName)
// 负载之后请求真实的url
// com.netflix.client.AbstractLoadBalancerAwareClient#executeWithLoadBalancer(....)
.executeWithLoadBalancer(ribbonRequest,requestConfig)
.toResponse();
}
catch (ClientException e) {
....
throw new RuntimeException(e);
}
}
com.netflix.client.AbstractLoadBalancerAwareClient#executeWithLoadBalancer(....)
public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
LoadBalancerCommand command = buildLoadBalancerCommand(request, requestConfig);
try {
// 在com.netflix.loadbalancer.reactive.LoadBalancerCommand#submit 中会根据 负载均衡算法之后获取到真实的ip地址
return command.submit(
new ServerOperation() {
@Override
// 传入的server 就是真实的ip
public Observable call(Server server) {
URI finalUri = reconstructURIWithServer(server, request.getUri());
// 路径替换把原本 http://client-name/xxxx 地址改为 http://127.0.0.1:9090/xxxx
S requestForServer = (S) request.replaceUri(finalUri);
try {
// 请求父类中的 execute 方法，也就是 上面 lbClient(clientName) 返回的 FeignLoadBalancer
return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig));
}
catch (Exception e) {
return Observable.error(e);
}
}
})
.toBlocking()
.single();
} catch (Exception e) {
Throwable t = e.getCause();
if (t instanceof ClientException) {
throw (ClientException) t;
} else {
throw new ClientException(e);
}
}
}
org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer#execute
@Override
public RibbonResponse execute(RibbonRequest request, IClientConfig configOverride)
throws IOException {
Request.Options options;
.....
// 这里的 request 就是 `org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient#execute`
// 封装的FeignLoadBalancer.RibbonRequest
// request.client() 返回就是 feign.Client.Default
Response response = request.client().execute(request.toRequest(), options);
return new RibbonResponse(request.getUri(), response);
}
feign.Client.Default#execute
@Override
public Response execute(Request request, Options options) throws IOException {
HttpURLConnection connection = convertAndSend(request, options);
return convertResponse(connection).toBuilder().request(request).build();
}
这里的request 中 url 就是真实的url资源路径了
现在屡屡逻辑
org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient和feign.Client.Default
都实现了 feign.Client 接口，但是 LoadBalancerFeignClient 实际上调用的还是 feign.Client.Default，无非做了自己处理（负载），有些类似于静态代理
那么上面的问题就只剩下能否替换的问题了
@Configuration
class DefaultFeignLoadBalancedConfiguration {
@Bean
@ConditionalOnMissingBean
public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
SpringClientFactory clientFactory) {
return new LoadBalancerFeignClient(new Client.Default(null, null),
cachingFactory, clientFactory);
}
}
这就不需要我来过多解释了，我们只需要自定义一个 LoadBalancerFeignClient 或者 实现Client的类就行 然后注入就行
实现代码
我选择的是 自定义实现一个 Client,去继承 feign.Client.Default
@Slf4j
public class InFeignClient extends Client.Default {
/**
*/
public InFeignClient(SSLSocketFactory sslContextFactory, HostnameVerifier hostnameVerifier) {
super(sslContextFactory, hostnameVerifier);
}
@Override
public Response execute(Request request, Request.Options options) throws IOException {
try {
return super.execute(request, options);
} catch (IOException e) {
log.warn(" 请求 {} 异常 ======> {}", request.url(), e.getMessage());
throw e;
}
}
}
然后将这个类替换
@Component
public class RestConfig {
public CachingSpringLoadBalancerFactory cachingLBClientFactory(
SpringClientFactory factory) {
return new CachingSpringLoadBalancerFactory(factory);
}
@Bean
public Client feignClient(SpringClientFactory clientFactory) {
CachingSpringLoadBalancerFactory bean = cachingLBClientFactory(clientFactory);
return new LoadBalancerFeignClient(new InFeignClient(null, null), bean, clientFactory);
}
}