perf: replace format!() allocations in on_headers hot path#1200
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FlorentinDUBOIS wants to merge 3 commits intomainfrom
Open
perf: replace format!() allocations in on_headers hot path#1200FlorentinDUBOIS wants to merge 3 commits intomainfrom
FlorentinDUBOIS wants to merge 3 commits intomainfrom
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Replace heap-allocating format!() calls with write!() into reusable Vec<u8> buffers and itoa for stack-based integer formatting. This eliminates up to 7 String allocations per HTTP request in the header editing callback that profiling showed taking up to 75% of readable(). Changes: - Add itoa dependency for stack-based u16 port formatting - Add write_forwarded_for_by() and write_forwarded_suffix() helpers that build Forwarded header values into a Vec<u8> without format!() - Replace format!() in X-Forwarded-For, Forwarded, Set-Cookie with write!() into reusable hdr_buf + Store::from_vec(take(&mut buf)) - Replace public_port.to_string() with itoa::Buffer for X-Forwarded-Port - Replace val.to_string() with ToOwned::to_owned for sticky cookie - Keep self.id.to_string() for Sozu-Id (Ulid encoding is already optimized with pre-allocated crockford base32 buffer)
- Remove `unsafe { from_utf8_unchecked(...) }.as_bytes()` round-trip
when extending hdr_buf with existing header data — the data is
already `&[u8]`, so the unsafe conversion to `&str` and back was
pointless and introduced gratuitous unsafety.
- Move `hdr_buf` allocation inside `if let Some(peer_addr)` block to
avoid a 128-byte heap allocation when `session_address` is `None`.
- Fix misleading "Reusable buffer" comment — the buffer's ownership
is transferred via `take`, so it is not actually reused.
- Remove unused `from_utf8_unchecked` import.
Signed-off-by: Florentin Dubois <florentin.dubois@clever.cloud>
Align itoa dependency version with workspace convention: "^x.y.z" instead of "^x.y". Signed-off-by: Florentin Dubois <florentin.dubois@clever.cloud>
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Summary
format!()allocations withitoa::Buffer,write!()intoVec<u8>, andextend_from_sliceitoaworkspace dependency (zero-dep, stack-based integer formatting)write_forwarded_for_byandwrite_forwarded_suffixhelpers to reduce code duplicationReview fixes applied
unsafe { from_utf8_unchecked(...) }.as_bytes()roundtrip — now uses&[u8]directlyVec::with_capacity(128)allocation into conditional scope (was allocating on every request even withoutsession_address)Closes #1140
Test plan
cargo test --workspacepassescargo clippy --workspaceclean