feat(client): retry + circuit-breaker (#39)#244
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Adds opt-in retry-with-exponential-backoff and a three-state circuit breaker (CLOSED/OPEN/HALF_OPEN) to HttpTestClient so chaos tests do not fail on the transient connection errors they are designed to create. ABI-conservative: new RetryPolicy / CircuitBreakerConfig structs default to no-op behaviour (max_retries=0, failure_threshold=0), so existing single-argument constructions compile and behave identically. Only status==0 (transport failure) is retried; deliberate 4xx/5xx replies are returned unchanged. Covered by test/src/test_http_client_retry_unit.cpp using the in-process MockServer pattern from test_http_client_unit.cpp. Closes #39 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- Move `run_with_retry` from anonymous-namespace free function to a private
static template member of `HttpTestClient` so it can refer to the
private `CircuitBreaker` nested type without exposing it publicly.
- Change template signature from `Fn&& fn` (forwarding reference never
std::forward'd, and invoked in a loop) to `Fn func` by value — safe for
the lambda callsites and removes the clang-tidy warning.
- Rename constructor and ctor params `cb` → `breaker_cfg` to satisfy
identifier-length checks on public API.
- Add `std::uint8_t` underlying-type to `BreakerState` enum.
- Drop redundant `{}` initializer on `opened_at_` (value-initialised by
default).
- Rename test-local identifiers (`p`/`c`/`cb`) to descriptive names and
add `const` to value-only locals to satisfy
`misc-const-correctness` / `readability-identifier-length`.
- Use `auto` for the static_cast<double>() result of base_delay_ms.
- clang-format -i over all three changed files for the format check.
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Summary
HttpTestClient.status == 0) are retried; deliberate 4xx/5xx responses pass through unchanged.min(base * mult^attempt, cap) * uniform(0.5, 1.5); no sleep after the final attempt.RetryPolicyandCircuitBreakerConfigstructs default to no-op behaviour (max_retries = 0,failure_threshold = 0), so existing single-argHttpTestClient("...")constructions compile and behave identically — the change is ABI-conservative on purpose (cf. PR refactor: expose timeout constants as constructor params (#81) #231 cascade).ABI / migration
<chrono>and forward-declares a privateCircuitBreaker(pimpl-style), so<atomic>,<mutex>,<random>stay in the.cpp.Test plan
test/src/test_http_client_retry_unit.cppcovers default-policy constants, retry exhaustion against refused ports, HTTP-error non-retry, breaker trip/half-open/disabled paths via the in-processMockServerpattern.projectcharybdis_testsbuilds and discovers all new tests.HttpTestClientUnit/HttpTestClientOnlinetests still pass (default policy means zero behaviour drift).Closes #39
Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com