perf: Skip request-body compression for already-compressed content types

[vdusek]

What

_prepare_request_call now checks the request's Content-Type before compressing the body and skips compression for media types that already carry their own compression:

• any image/*, audio/*, or video/* type,
• archives (application/zip, application/gzip, application/x-7z-compressed, rar, bzip2, xz, zstd, jar),
• web fonts (font/woff, font/woff2).

Types with a +json/+xml structured suffix stay compressible, so image/svg+xml is not caught by the image/ prefix. The media type is normalized before matching (parameters stripped, lowercased, trimmed). When compression is skipped, any caller-supplied Content-Encoding header is dropped as well — the body goes out verbatim, so the header would otherwise misdescribe it.

Why

The client compressed every request body unconditionally. For already-compressed payloads that burns CPU and holds a second full copy of the body in memory, while typically producing output slightly larger than the input. Key-value store records — screenshots, video, archives — are exactly this case.

End-to-end set_record with a 200 MB incompressible payload:

Content type	Peak RSS	Wall / CPU
application/octet-stream (unchanged)	604 MB - 3.02x	7.8 s / 6.9 s user
image/png (new path)	403 MB - 2.02x	1.05 s / 0.40 s user

application/octet-stream is deliberately not on the list: it is the catch-all for unknown binary, which may well be uncompressed data. It is also the encoder's default when no content_type is passed, so the optimization only applies when the caller sets an accurate content type — documented in the compression concept page.

The remaining 2x comes from handing a bytes body to impit's content=, tracked separately in #972.

Notes

This overlaps with #934 (skip compression for small payloads) — both add a condition to the same block in _prepare_request_call. Whichever lands second needs the two conditions combined.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.70%. Comparing base (cb8fe24) to head (be16625).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #987      +/-   ##
==========================================
+ Coverage   94.65%   94.70%   +0.04%     
==========================================
  Files          58       58              
  Lines        5259     5323      +64     
==========================================
+ Hits         4978     5041      +63     
- Misses        281      282       +1     

Flag	Coverage Δ
integration	92.18% <92.00%> (-0.25%)	⬇️
unit	84.23% <100.00%> (+0.19%)	⬆️

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[Mantisus]

LGTM. Only a small suggestion.