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Loss of ThreadLocal Information in OpenFeign with Resilience4j Circuit Breaker

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評価

難易度
5/5
見積もり時間
1週間以上
初心者へのやさしさ
25/100
issue の種類
機能追加
明瞭さ
説明が足りない
活発さ
停滞
技術スタック
java, spring
領域
api, backend

調査の方向性

まず、説明されている2つの拡張ポイントである FeignCircuitBreakerInvocationHandler#asSupplier と Resilience4JCircuitBreakerFactory#configureExecutorService を読みます。コンテキスト伝播の動作を比較し、何も実装する前にサポートされている API を明確にします。非同期の circuit breaker 実行中にリクエストの ThreadLocal 情報を保持しつつ、タスク間に漏洩させないための合意済みのアプローチが決まれば完了とします。

索引モデルが issue の本文から書いたものです。

説明

enhancement help wanted

Is your feature request related to a problem? Please describe.

Issue Summary:
I encountered an issue while using Spring Cloud OpenFeign. When configuring circuit breaking (resilience4j), the FeignCircuitBreakerInvocationHandler submits our Feign client to be processed by an asynchronous thread, resulting in the loss of ThreadLocal information in the request context. Do you have any suggestions for resolving this issue?

Business Scenario:
In a Spring Web project, we have a custom RequestInterceptor that retrieves information stored in ThreadLocal before making a request. This information is used to populate RequestHeader and is then passed to downstream services. However, after introducing resilience4j as a circuit breaker in OpenFeign, resilience4j executes requests in a thread pool, causing ThreadLocal information to be lost.

Describe the solution you'd like

Proposal:
Therefore, I propose adding a hook (template method) within the org.springframework.cloud.openfeign.FeignCircuitBreakerInvocationHandler#asSupplier method in OpenFeign. This hook would allow the application service to retrieve the ThreadLocal object and, within the Supplier, set the ThreadLocal to the executing thread's ThreadLocal, similar to how it is done with RequestContextHolder. Is this approach feasible?

Below is sample code, assuming SubjectContext is a hook

private Supplier<Object> asSupplier(final Method method, final Object[] args) {
    final RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
    final Thread caller = Thread.currentThread();
    // Sample code
    **SubjectContext context = SubjectContext.getContext();**
    return () -> {
        boolean isAsync = caller != Thread.currentThread();
        try {
            if (isAsync) {
                RequestContextHolder.setRequestAttributes(requestAttributes);
                **SubjectContext.setContext(context);**
            }
            return dispatch.get(method).invoke(args);
        }
        catch (RuntimeException throwable) {
            throw throwable;
        }
        catch (Throwable throwable) {
            throw new RuntimeException(throwable);
        }
        finally {
            if (isAsync) {
                RequestContextHolder.resetRequestAttributes();
                **SubjectContext.clear();**
            }
        }
    };
}

Describe alternatives you've considered

I have also considered using a hook provided by resilience4j during application startup, specifically within org.springframework.cloud.circuitbreaker.resilience4j.Resilience4JCircuitBreakerFactory#configureExecutorService. By passing a custom thread pool object here, I could potentially propagate the ThreadLocal information. Sample code is as follows:

@Configurable
@AllArgsConstructor
public class CircuitBreakerConfiguration implements ApplicationRunner {

    private final Resilience4JCircuitBreakerFactory factory;
    
    @Override
    public void run(ApplicationArguments args) throws Exception {

        ContextThreadPoolExecutor contextThreadPoolExecutor = 
                new ContextThreadPoolExecutor(2, 5, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<>(1024));

        // **change ThreadPoolExecutor**
        factory.configureExecutorService(contextThreadPoolExecutor);
    }
    
    public static class ContextThreadPoolExecutor extends ThreadPoolExecutor {

        public ContextThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
            super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
        }

        public void execute(Runnable command) {
            super.execute(wrap(command));
        }

        private static Runnable wrap(Runnable runnable) {
            **SubjectContext context = SubjectContext.getContext();**
            return () -> {
                **SubjectContext.setContext(context);**
                try {
                    runnable.run();
                } finally {
                    **SubjectContext.clear();**
                }
            };
        }
    }
}

However, I find it less elegant, and I believe resolving it within the asSupplier() method of OpenFeign would be more versatile and applicable to a broader range of scenarios.

Additional context
spring-cloud-openfeign-3.1.2

主要言語
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