📄 feign 自动降级功能 _ PIGCLOUD
](https://www.pig4cloud.com/)
产品
商业版
生态🔥
📄 feign 自动降级功能
pigcloud
# 版本说明
此改造针对 pigx 3.4 及之前版本， feign-hystrix。 3.5 以后使用的是 sentinel 支持统一的降级策略 PigxUrlBlockHandler
# 目的
先来看默认的 feign service 是要求怎么做的。feign service 定义一个 factory 和 fallback 的类
1
2
3
4
5
6
7
| @FeignClient(value = ServiceNameConstants.UMPS_SERVICE, fallbackFactory = RemoteLogServiceFallbackFactory.class)
public interface RemoteLogService {}
Copied!
|
在 Spring Cloud 使用 feign 的时候，需要明确指定 fallback 策略，不然会提示错误。 但是我们大多数情况的 feign 降级策略为了保证幂等都会很简单，输出错误日志即可。 类似如下代码，在企业中开发非常不方便
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
| @Slf4j
@Component
public class RemoteLogServiceFallbackImpl implements RemoteLogService {
@Setter
private Throwable cause;
@Override
public R<Boolean> saveLog(SysLog sysLog, String from) {
log.error("feign 插入日志失败", cause);
return null;
}
}
Copied!
|
# 自定降级效果
1
2
3
4
5
6
7
| @FeignClient(value = ServiceNameConstants.UMPS_SERVICE)
public interface RemoteLogService {}
Copied!
|
- Feign Service 完成同样的降级错误输出
- FeignClient 中无需定义无用的 fallbackFactory
- FallbackFactory 也无需注册到 Spring 容器中
# 核心源码
- 注入我们个性化后的 Feign
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
| @Configuration
@ConditionalOnClass({HystrixCommand.class, HystrixFeign.class})
protected static class HystrixFeignConfiguration {
@Bean
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
@ConditionalOnProperty("feign.hystrix.enabled")
public Feign.Builder feignHystrixBuilder(FeignContext feignContext) {
return PigxHystrixFeign.builder(feignContext)
.decode404()
.errorDecoder(new PigxFeignErrorDecoder());
}
}
Copied!
|
- PigxHystrixFeign.target 方法是根据@FeignClient 注解生成代理类的过程，注意注释
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
| @Override
public <T> T target(Target<T> target) {
Class<T> targetType = target.type();
FeignClient feignClient = AnnotatedElementUtils.getMergedAnnotation(targetType, FeignClient.class);
String factoryName = feignClient.name();
SetterFactory setterFactoryBean = this.getOptional(factoryName, feignContext, SetterFactory.class);
if (setterFactoryBean != null) {
this.setterFactory(setterFactoryBean);
}
Class<?> fallback = feignClient.fallback();
if (fallback != void.class) {
return targetWithFallback(factoryName, feignContext, target, this, fallback);
}
Class<?> fallbackFactory = feignClient.fallbackFactory();
if (fallbackFactory != void.class) {
return targetWithFallbackFactory(factoryName, feignContext, target, this, fallbackFactory);
}
return build().newInstance(target);
}
Copied!
|
- 构建 feign 客户端执行 PigxHystrixInvocationHandler 的增强
1
2
3
4
5
6
7
8
9
10
11
| Feign build(@Nullable final FallbackFactory<?> nullableFallbackFactory) {
super.invocationHandlerFactory((target, dispatch) ->
new PigxHystrixInvocationHandler(target, dispatch, setterFactory, nullableFallbackFactory));
super.contract(new HystrixDelegatingContract(contract));
return super.build();
}
Copied!
|
- PigxHystrixInvocationHandler.getFallback() 获取降级策略
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
| @Override
@Nullable
@SuppressWarnings("unchecked")
protected Object getFallback() {
if (fallbackFactory == null) {
fallback = PigxFeignFallbackFactory.INSTANCE.create(target.type(), getExecutionException());
} else {
fallback = fallbackFactory.create(getExecutionException());
}
}
Copied!
|
- PigxFeignFallbackFactory.create 动态代理逻辑
1
2
3
4
5
6
7
8
9
10
11
12
13
| public T create(final Class<?> type, final Throwable cause) {
return (T) FALLBACK_MAP.computeIfAbsent(type, key -> {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(key);
enhancer.setCallback(new PigxFeignFallbackMethod(type, cause));
return enhancer.create();
});
}
Copied!
|
- PigxFeignFallbackMethod.intercept， 默认的降级逻辑，输出降级方法信息和错误信息，并且把错误格式
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
| public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) {
log.error("Fallback class:[{}] method:[{}] message:[{}]",
type.getName(), method.getName(), cause.getMessage());
if (R.class == method.getReturnType()) {
final R result = cause instanceof PigxFeignException ?
((PigxFeignException) cause).getResult() : R.builder()
.code(CommonConstants.FAIL)
.msg(cause.getMessage()).build();
return result;
}
return null;
}
Copied!
|
📄 服务配置 cors 跨域 📄 配置文件加解密
