@SentinelDegrade注解不生效

[shelltea]

1. 增加Sentinel依赖和配置，启动熔断降级功能；

        <dependency>
            <groupId>com.github.lianjiatech</groupId>
            <artifactId>retrofit-spring-boot-starter</artifactId>
            <version>2.3.9</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-core</artifactId>
            <version>1.8.3</version>
        </dependency>

retrofit.degrade.degrade-type = sentinel

2. 在接口上配置@SentinelDegrade注解，异常数超过1触发降级，如下：

@SentinelDegrade(grade = 2, count = 1)
@RetrofitClient(baseUrl = "https://api.com", connectTimeoutMs = 3000,
        fallback = ApiFallback.class, fallbackFactory = ApiFallbackFactory.class)
public interface Api {

}

3. 在单元测试中循环调用此接口的方法，通过抛出java.net.ConnectException异常模拟调不通的情况，未触发ApiFallback中的代码，在Sentinel的${user_home}/logs/csp日志目录中发现异常未计数：

日志的第7个数值为异常数

4. 通过分析代码发现SentinelRetrofitDegrade类中未通过Tracer对异常进行统计：

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        Method method = Objects.requireNonNull(request.tag(Invocation.class)).method();
        SentinelDegrade sentinelDegrade = AnnotationExtendUtils.findMergedAnnotation(method, method.getDeclaringClass(),
                SentinelDegrade.class);
        if (!needDegrade(sentinelDegrade)) {
            return chain.proceed(request);
        }
        String resourceName = parseResourceName(method);
        Entry entry = null;
        try {
            entry = SphU.entry(resourceName, ResourceTypeConstants.COMMON_WEB, EntryType.OUT);
            return chain.proceed(request);
        } catch (BlockException e) {
            throw new RetrofitBlockException(e);
        } finally {
            if (entry != null) {
                entry.exit();
            }
        }
    }

5. 在Sentinel提供的sentinel-okhttp-adapter中的代码，包含了Tracer记录的代码：
   https://github.com/alibaba/Sentinel/blob/master/sentinel-adapter/sentinel-okhttp-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/okhttp/SentinelOkHttpInterceptor.java

[shelltea]

在对SentinelRetrofitDegrade类进行了以下修改后，可以正常记录异常数，并触发熔断：

@Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        Method method = Objects.requireNonNull(request.tag(Invocation.class)).method();
        SentinelDegrade sentinelDegrade = AnnotationExtendUtils.findMergedAnnotation(method, method.getDeclaringClass(),
                SentinelDegrade.class);
        if (!needDegrade(sentinelDegrade)) {
            return chain.proceed(request);
        }
        String resourceName = parseResourceName(method);
        Entry entry = null;
        try {
            entry = SphU.entry(resourceName, ResourceTypeConstants.COMMON_WEB, EntryType.OUT);
            return chain.proceed(request);
        } catch (BlockException e) {
            throw new RetrofitBlockException(e);
        } catch (IOException | RetrofitException ex) {
            Tracer.traceEntry(ex, entry);
            throw ex;
        } finally {
            if (entry != null) {
                entry.exit();
            }
        }
    }

5次异常，995次拦截。

通过上述的改动，可以使@Retry和@SentinelDegrade组合使用，例如：

@SentinelDegrade(grade = 2, count = 1)
@RetrofitClient(baseUrl = "https://api.com", connectTimeoutMs = 3000,
        fallback = Fallback.class, fallbackFactory = FallbackFactory.class)
public interface TexSmartApi {
    @Retry(intervalMs = 20)
    @POST("api")
    Response api(@Body Request request);
}

需要在方法调用地方对Retry Failed的RetrofitException进行捕获。

可以先进行2次重试，然后抛出Retry Failed的RetrofitException，一共进行15次请求（minRequestAmount = 5）尝试后触发降级。

[chentianming11]

厉害了，分析的很深入。我在SentinelRetrofitDegrade加上Tracer，再发一个版本。

[chentianming11]

感觉对于非BlockException，都需要trace

2.3.10版本已修复

[shelltea]

@chentianming11 升级到了2.3.10，测试可以熔断。👍