Prevent duplicate cache error handler execution in FeignCachingInvocationHandlerFactory

Contribution Overview

The Engineering Context

This contribution was made to the spring-cloud/spring-cloud-openfeignopen-source repository. The work involved understanding the existing codebase, identifying the underlying engineering problem, implementing a focused solution, and validating the change against the project's existing behaviour and testing standards.

Original Issue

Cache error handling can be executed more than once for Feign clients using caching.

The interaction between Spring Cache and Feign's caching infrastructure could result in duplicate cache interception and repeated execution of cache error handling logic.

Engineering Problem

Understanding the Problem

Caching around Feign clients could involve both Spring Cache interception and FeignCachingInvocationHandlerFactory, causing cache-related handling to be invoked multiple times during a single operation.

Solution

Implementation Approach

Added a ThreadLocal-based guard around the Feign caching invocation path to prevent nested cache interception from executing repeatedly, while ensuring the guard is removed after processing completes. The PR also documents caching behaviour and related limitations for Feign clients.

Technologies

Engineering Stack