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https://issues.apache.org/jira/browse/CAMEL-24137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18097776#comment-18097776
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Claus Ibsen commented on CAMEL-24137:
-------------------------------------
Phase 1 merged: https://github.com/apache/camel/pull/24957
Covers sub-items Z1, Z4, Z5, Z6, Z7, Z8.
> Circuit Breaker EIP - modernization umbrella (drop vavr, async completion,
> virtual threads, duration units, breaker events)
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-24137
> URL: https://issues.apache.org/jira/browse/CAMEL-24137
> Project: Camel
> Issue Type: Improvement
> Components: eip
> Affects Versions: 4.21.0
> Reporter: Federico Mariani
> Assignee: Claus Ibsen
> Priority: Major
> Fix For: 4.22.0
>
> Attachments: camel-circuitbreaker-eip-review-2026-07.md
>
>
> Umbrella for modernization suggestions from a review of the Circuit Breaker
> EIP (core model, camel-resilience4j, camel-microprofile-fault-tolerance).
> Full review document attached.
> h3. Z1. Drop Vavr from camel-resilience4j
> resilience4j 2.x removed its Vavr dependency, but camel-resilience4j re-adds
> {{vavr}} + {{vavr-match}} 1.0.0 solely for one
> {{Try.ofCallable(...).andThen(...).recover(...).get()}} chain in
> {{ResilienceProcessor.process()}}. A plain try/catch removes two runtime jars.
> h3. Z2. True async processing
> Both processors implement the async contract but are fully blocking: they
> always {{callback.done(true); return true}}, and the timeout path parks the
> calling thread on {{future.get()}} while a second thread runs the work (two
> threads per in-flight message). Resilience4j has CompletableFuture-based
> decorators and SmallRye supports async guard calls; completing the
> {{AsyncCallback}} from the worker would free consumer threads exactly when
> the breaker is protecting a slow downstream - the scenario the EIP exists for.
> h3. Z3. Virtual threads
> The timeout executor (resilience4j) and thread-offload executor (FT) are
> natural fits for virtual threads on JDK 21+ (Camel already has {{ThreadType}}
> support in the ExecutorServiceManager); this would make the thread-per-call
> model cheap even without Z2.
> h3. Z4. Unit/type consistency in the resilience4j configuration model
> {{waitDurationInOpenState}} and {{slowCallDurationThreshold}} are integer
> *seconds*, while {{timeoutDuration}} and {{bulkheadMaxWaitDuration}} are
> integer *millis*. The FT model already uses {{javaType=java.time.Duration}}
> with {{parseDuration}} (accepts {{5s}}, {{500ms}}). Migrating the
> resilience4j options to duration strings (with an upgrade-guide note) removes
> a recurring user trap.
> h3. Z5. Expose missing resilience4j 2.x features
> * {{maxWaitDurationInHalfOpenState}};
> * custom record/ignore predicate beans (currently only class-name lists);
> * referencing existing {{TimeLimiter}} / {{Bulkhead}} beans (only
> {{CircuitBreaker}} is referenceable today);
> * optional ThreadPoolBulkhead;
> * biggest observability win: bridge the resilience4j {{EventPublisher}}
> (state transitions, not-permitted calls) to Camel events / a RoutePolicy
> hook, so users do not have to poll JMX to learn the breaker opened.
> h3. Z6. Deprecate {{onFallbackViaNetwork}}
> Hystrix-era leftover; both remaining implementations throw
> {{UnsupportedOperationException}} at route init. The DSL method and model
> option exist only to fail.
> h3. Z7. Clarify {{micrometerEnabled}} scope
> It is only acted upon by camel-main's global {{detectResilience4jMicrometer}}
> (reading the *default* configuration); set inline on a route's
> {{resilience4jConfiguration}} it does nothing per-EIP. Document as
> global-only or wire it per-processor.
> h3. Z8. Test gaps
> No test asserts {{RESPONSE_TIMED_OUT}} in either module; no pooled-mode test
> with a consumer-created exchange (see CAMEL-24133); no test for fallback
> visibility of guard-level exception causes.
> _Filed by Claude Code on behalf of Federico Mariani (fmariani)_
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