Skip oversized Link preload header in Optimization Detective#2572
Skip oversized Link preload header in Optimization Detective#2572faisalahammad wants to merge 1 commit into
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- Add od_get_maximum_link_response_header_length() with filter od_link_response_header_max_length (default 4KB) - Skip sending the Link response header when it would exceed the limit, falling back to the existing HTML link tag output - Add tests covering the new getter and the HTML fallback Some reverse proxies fail requests with an oversized response header, which can happen when responsive images have long or non-ASCII filenames across multiple viewport breakpoints. The HTML link tags already carry the same preload info, so skipping the header when it is too large keeps the request from failing without losing preload behavior. Fixes WordPress#2304
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[Plugin] Optimization Detective
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## trunk #2572 +/- ##
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+ Coverage 70.35% 70.41% +0.05%
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Files 91 91
Lines 7867 7882 +15
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+ Hits 5535 5550 +15
Misses 2332 2332
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Summary
Fixes #2304
Image Prioritizer (via Optimization Detective) can generate a
Link: rel=preloadresponse header that gets too large when responsive images have long or non-ASCII filenames across multiple viewport breakpoints with different LCP images. Some reverse proxies (Nginx) reject the response with "upstream sent too big header", causing intermittent 502s for logged-in users.Relevant technical choices
od_optimize_template_output_buffer()inoptimization.phpalready sends both aLinkresponse header and equivalent HTML<link>tags for every collected preload link, unconditionally. The HTML tags carry the same preload info, so the fix skips sending the header when it would exceed a length cap and just relies on the HTML tags in that case.od_get_maximum_link_response_header_length(), mirroring the existingod_get_maximum_url_metric_size()pattern (filterod_link_response_header_max_length, default 4 KB,_doing_it_wrong()fallback on invalid values).header()call inoptimization.php; theappend_head_html()call stays unconditional so preloading keeps working through HTML tags when the header is skipped.docs/hooks.md.headers_sent()is alwaystruein this repo's PHPUnit harness, so the actualheader()call itself can't be asserted on in automated tests (this was already true before this change, nothing here regresses that).Testing
Manual: page with responsive images across several breakpoints resolving to different LCP images with long filenames, logged in, uncached request — confirmed no single
Linkheader exceeds the cap and<link rel="preload">tags are still present in<head>. Verified the filter raises/lowers the cap as expected.Automated:
npm run test-php:optimization-detective(360 tests pass),composer lint:optimization-detective(clean),npm run phpstan(no errors).Use of AI Tools
Used an AI coding assistant (Claude Code) to investigate the codebase, draft the implementation, tests, and docs, and to run the test/lint/static-analysis suite. I reviewed the change, ran the tests myself, and take responsibility for the code.