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perf(pdf-server): share cache across server instances and dedupe form parsing#637
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perf(pdf-server): share cache across server instances and dedupe form parsing#637
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… parsing In stateless HTTP deployments createServer() is called per request, so the per-instance pdfCache and the 4 MB viewer HTML were discarded after every call. Hoist both to module scope. Also refactor extractFormSchema/extractFormFieldInfo to accept an already-parsed PDFDocumentProxy so display_pdf downloads and parses the PDF once instead of twice.
The module-level sharedPdfCache could grow unbounded within the 60s lifetime window under a burst of distinct URLs. Track running total bytes and evict least-recently-used entries on insert when it would exceed CACHE_MAX_TOTAL_BYTES (256MB). getCacheEntry now bumps the accessed entry to the end of insertion order so eviction targets the LRU entry rather than the oldest insert. createPdfCache takes an optional maxTotalBytes for testability.
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Summary
Three perf fixes for the pdf-server when run behind a stateless HTTP transport (where
createServer()is invoked on every request):sharedPdfCache—createPdfCache()is now called once at module load and reused by every server instance, instead of being created (and immediately discarded) per request. This letsread_pdf_byteschunk reads hit the cache across requests, avoiding repeated full-body downloads when the upstream origin doesn't honor Range.mcp-app.html— the ~4 MB viewer HTML is read from disk once (cachedAppHtml ??= ...) instead of on every resource read.display_pdf—extractFormSchemaandextractFormFieldInfonow accept an already-parsedPDFDocumentProxy.display_pdffetches the bytes once, callspdfjs.getDocument()once, passes the doc to both extractors, anddestroy()s it in afinally. Previously each extractor independently downloaded the full PDF and parsed it.Behavior note
Both extractors now run inside a single try block, so if schema extraction throws, field-info extraction is also skipped (previously each had its own try/catch). Risk is low: the only throw point inside
extractFormSchema(getFieldObjects) is already caught internally and returns an empty schema rather than propagating.Tests
bun test examples/pdf-server— 177 pass, 0 fail, 1 pre-existing skip. Build (tsc + vite + bun bundle) and prettier check both clean.