Spring Retry: Understanding ExhaustedRetryException Behavior

When working with Spring Retry, you might encounter an unexpected ExhaustedRetryException even when the first method invocation fails with an exception that isn't covered by the retryFor attribute. This article delves into this behavior, providing clarity and guidance on how to handle it effectively.

The Issue: Unexpected ExhaustedRetryException

In Spring Retry, the ExhaustedRetryException typically indicates that all retry attempts for a method have been exhausted. However, a peculiar situation arises when using a recovery method in conjunction with the @Retryable annotation. Specifically, if the initial method invocation fails with an exception type not included in the retryFor attribute, an ExhaustedRetryException might still be thrown. This can be confusing, as it suggests retries were attempted when, in fact, they weren't.

Consider this scenario:

• A method is annotated with @Retryable, specifying retryFor with a particular set of exception types.
• A recovery method is also defined for this method.
• The first invocation of the method results in an exception not listed in retryFor.

In this situation, one might expect the recovery method to be invoked immediately, or the original exception to be propagated. However, Spring Retry throws an ExhaustedRetryException, wrapping the original exception. This behavior contradicts the expectation that ExhaustedRetryException should only occur after all retry attempts have been exhausted.

The core of the issue lies in how Spring Retry handles exceptions that don't match the retryFor conditions when a recovery method is present. Instead of immediately invoking the recovery method or propagating the original exception, it wraps the exception in an ExhaustedRetryException, potentially leading to misinterpretations and confusion.

Reproducing the Behavior

To better understand this behavior, consider a sample project demonstrating the issue:

@Service
public class WithRecoveryService {

    @Retryable(retryFor = IOException.class, maxAttempts = 3, recover = "recovery")
    public String retryableMethod() throws CustomException, IOException {
        System.out.println("retryableMethod called");
        throw new CustomException("Simulated custom exception");
    }

    @Recover
    public String recovery(CustomException e) {
        System.out.println("recovery method called");
        return "Recovered: " + e.getMessage();
    }
}

In this example, retryableMethod is annotated with @Retryable, specifying that retries should only occur for IOException. A CustomException is thrown, which is not included in the retryFor attribute. Despite this, an ExhaustedRetryException is thrown, even though no retries were attempted.

Analyzing the Code

In the retryableMethod example, the @Retryable annotation is configured to retry only for IOException. When a CustomException is thrown, Spring Retry's default behavior, in the presence of a recovery method, is to wrap this non-retryable exception in an ExhaustedRetryException. This is because the retry operations are considered 'exhausted' in the sense that the exception is not one that should be retried according to the retryFor configuration.

The recovery method recovery(CustomException e) is defined to handle the exception. However, the ExhaustedRetryException is thrown before the recovery method is invoked in the standard flow. This behavior might not be immediately intuitive, as one might expect the recovery method to be directly invoked when a non-retryable exception occurs.

Demonstrating the Issue

To further illustrate the issue, consider the test case shouldNotThrowExhaustedRetry() in the provided example. This test case demonstrates that even though the method fails on the first attempt with an exception not included in retryFor, Spring Retry still throws an ExhaustedRetryException. This is counterintuitive because no retry attempts were made, and the exception is explicitly not retryable according to the configuration.

@Test
public void shouldNotThrowExhaustedRetry() {
    try {
        withRecoveryService.retryableMethod();
        fail("Expected ExhaustedRetryException was not thrown");
    } catch (ExhaustedRetryException e) {
        System.out.println("Caught: " + e.getMessage());
        assertThat(e.getCause(), instanceOf(CustomException.class));
    }
}

This test case captures the essence of the problem: an ExhaustedRetryException is thrown even when the exception is not meant to be retried. This behavior is inconsistent with the common understanding of what ExhaustedRetryException signifies, leading to potential confusion and debugging challenges.

Expected Behavior vs. Actual Behavior

The expected behavior in such cases would be either:

1. The recovery method should be triggered immediately.
2. The original exception should be propagated without being wrapped in an ExhaustedRetryException.

However, the actual behavior deviates from this expectation. Spring Retry wraps the original exception in an ExhaustedRetryException, which can be misleading. It implies that retry attempts were made and exhausted, which is not the case when the exception doesn't match the retryFor conditions.

This discrepancy between expected and actual behavior highlights the need for a clearer understanding of Spring Retry's exception handling, particularly when recovery methods are involved.

Why This Happens

The reason for this behavior lies in Spring Retry's internal mechanisms for handling exceptions. When a recovery method is defined, Spring Retry assumes that all exceptions, even those not specified in retryFor, should be handled in some way. It treats the non-matching exception as a condition where retry attempts have been