[strawgate]

Follow-up to #628 (gRPC framing).

Changes

• Compressed flag semantics: The flag was set from self.compression == Compression::Zstd, but it should reflect whether the payload is actually compressed. If the compressor wasn't initialized, the payload falls back to uncompressed and the flag must be 0x00. Fixed to Zstd && compressor.is_some().
• Pre-allocate grpc_buf: Now initialized at 64 KiB to match encoder_buf / compress_buf and avoid reallocation on first use.
• u32::try_from for payload length: Replaces silent as u32 truncation with a clear panic for pathological >4 GiB payloads.
• New test grpc_send_batch_frames_payload: Covers the full encode_batch → write_grpc_frame path, validating the frame header against the actual encoded protobuf bytes.

Test plan

• cargo test -p logfwd-output — 59 tests pass (includes new test)
• cargo clippy -p logfwd-output -- -D warnings — clean
• cargo fmt --check -p logfwd-output — clean

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• crates/logfwd-output/src/otlp_sink.rs

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Walkthrough

Updated gRPC framing and buffer handling in crates/logfwd-output/src/otlp_sink.rs. OtlpSink::new now preallocates grpc_buf with 64 KiB. OutputSink::send_batch computes payload_is_compressed as (self.compression == Compression::Zstd) && self.compressor.is_some() and uses it when framing and when setting the Content-Encoding: zstd header. write_grpc_frame now checks payload length with u32::try_from(payload.len()).expect("gRPC message payload must be < 4 GiB") before writing the 4-byte big-endian length prefix. Added a unit test encode_and_frame_payload verifying the 5-byte gRPC header and exact protobuf payload in uncompressed mode.

Possibly related PRs

• strawgate/memagent PR 628 — modifies OTLP gRPC framing and send_batch behavior in the same crates/logfwd-output/src/otlp_sink.rs file, including adjustments to the 5-byte length-prefixed frame logic and tests.

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/logfwd-output/src/otlp_sink.rs`:
- Around line 824-865: Rename the test and update its doc comment to accurately
reflect that it validates the combination of OtlpSink::encode_batch and
write_grpc_frame rather than calling OtlpSink::send_batch; specifically update
the function name grpc_send_batch_frames_payload to something like
encode_batch_frames_payload or encode_and_frame_payload, and change the top
comment line to state that the test encodes via encode_batch and then frames
with write_grpc_frame (mention OtlpSink::encode_batch and write_grpc_frame in
the comment) so the test intent and coverage are precise and do not imply
send_batch is exercised.
- Around line 217-220: The code computes payload_is_compressed (based on
self.compression == Compression::Zstd && self.compressor.is_some()) but later
builds request headers using self.compression == Compression::Zstd, which can
falsely advertise compression when compressor is None; update header
construction to use payload_is_compressed (the same boolean passed to
write_grpc_frame) so the HTTP compression header matches the actual payload
compression state and ensure any branch that sets the compression-related header
checks payload_is_compressed (and not just self.compression) as well as avoid
setting compression headers when compressor is None.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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• crates/logfwd-output/src/otlp_sink.rs