perf(og): stream-parse <head> instead of buffering full 2 MB body - #1611
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perf(og): stream-parse <head> instead of buffering full 2 MB body#1611Sravanjangam wants to merge 1 commit into
Sravanjangam wants to merge 1 commit into
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readBoundedText buffered the entire response up to MAX_HTML_BYTES (2 MB) just to regex-scan it for OG meta tags that live in the first ~30 KB. At link-preview scale the peak RSS per request was ~6-8 MB and the first byte of any preview waited on a full-body fetch. readHeadText reads chunks into a small growing buffer, scans for </head> after each chunk, and cancels the reader as soon as it's seen. The cap drops to 64 KB; OG tags live entirely within that bound in practice. The 6 regex patterns in processHtml are unchanged and now run over a ~30 KB string instead of 2 MB. Fixes supermemoryai#1610.
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Fixes #1610.
Problem
apps/web/app/api/og/route.tsruns a regex-driven OG scraper on a 2 MB buffer when only the document<head>(~30 KB in practice) is actually needed.readBoundedTextalready streams the response, but it buffers every chunk into an array, merges them into a singleUint8Array, and thenTextDecoders the whole thing before returning. The function's own comment says "OG parsing only needs<head>, so cap the read rather than buffering the whole body" — but the implementation does the opposite.How it effects
Per
/api/ogrequest on the current code:chunks: Uint8Array[]+ 2 MB merged buffer + 2–4 MB UTF-16 string afterTextDecoder).</head>is discarded.At link-preview scale (a chat app unfurling 20 URLs in one message) peak RSS in the worker approaches 150–200 MB and the slowest fetch gates every other preview. The 2 MB cap is a correctness cap that doubles as the performance baseline, so making it a head-only cap of 64 KB is a free win.
Solution
Replace
readBoundedTextwithreadHeadText:</head>(case-insensitive) after every chunk.</head>is seen.null(→ existing 413 path) if the cap is hit before</head>closes.The 6 regex patterns in
processHtmlare unchanged — they just run over a 30–40 KB string instead of 2 MB, which is the actual win. The two call sites (main response and the single-level-redirect path) were updated to use the new function name; their error handling and status codes are unchanged.Tests
Apps/web has no test runner wired in (per recent maintainer preference), so the verification is a manual smoke harness run with
bun:Cases cover the happy path, realistic chunked delivery, mid-tag chunk boundaries, case-insensitive matching, the cap-exceeded path, and the empty-body edge case. The harness is in
/tmp/prs/og-head-smoke.mjs(not part of this PR) and can be re-run any time.Environment
extractImageUrlunused-function warning onmainis unchanged — baseline parity, not a regression from this diff)tsc --noEmitclean for the touched filefix/og-streaming-head-only, commitb95eebe2680e