refactor(tonic-xds): extract transport-agnostic RetryClassifier seam#2750
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refactor(tonic-xds): extract transport-agnostic RetryClassifier seam#2750LYZJU2019 wants to merge 1 commit into
LYZJU2019 wants to merge 1 commit into
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Split the retry layer into a transport-agnostic decision engine and a
transport-specific classifier so non-gRPC transports (e.g. plain HTTP)
can reuse the same retry machinery without duplicating a state machine.
- Add `RetryClassifier` trait: `is_retryable` decides retryability from
the response/error; a default-noop `prepare_retry` allows per-retry
request mutation.
- Add `GrpcRetryClassifier { retry_on }` implementing the previous gRPC
behavior verbatim (retryable connection error or retryable grpc-status,
plus stamping the `grpc-previous-rpc-attempts` header).
- Generalize `GrpcRetryPolicy` into `RetryPolicy<C>` holding the shared
decision state (attempt cap, backoff, body cloning) behind `ArcSwap`
and delegating transport decisions to the classifier. Tower's `Retry`
service still owns the retry state machine.
- Rename `GrpcRetryPolicyConfig` -> `RetryConfig` (retry_on moved to the
classifier) and `GrpcRetryBackoffConfig` -> `RetryBackoffConfig`.
- Keep `GrpcRetryPolicy = RetryPolicy<GrpcRetryClassifier>` as an alias
so existing callers are unchanged.
Items remain crate-internal (`pub(crate)`); public re-exports are
deferred to the transport-API step. Behavior is unchanged.
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Summary
Refactors the
tonic-xdsclient retry layer to be transport-agnostic so non-gRPC transports (e.g. plain HTTP) can reuse the same retry engine without duplicating a retry state machine. This is a non-breaking, standalone change: all items stay crate-internal (pub(crate)) and the existing gRPC behavior is preserved.Why
First step of generalizing the xDS retry layer so it can serve both gRPC and HTTP transports. Keeping the gRPC-specific logic (retryable codes +
grpc-previous-rpc-attemptsheader) behind the classifier keepstonic-xdstransport-agnostic while leaving gRPC the default.Testing
cargo build -p tonic-xds— clean (no warnings)cargo test -p tonic-xds— 340 passed, 0 failed (incl. retry unit tests +test_retry_once_on_unavailable)cargo clippy -p tonic-xds --all-targets— no new warnings in changed filescargo doc -p tonic-xds --no-deps(withRUSTDOCFLAGS=-D warnings) — cleanBehavior is unchanged; the diff is behavior-preserving.