LDEV-6446 Reduce heap when thumbnailing PDFs with large page images - #63
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shane-tw wants to merge 1 commit into
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LDEV-6446 Reduce heap when thumbnailing PDFs with large page images#63shane-tw wants to merge 1 commit into
shane-tw wants to merge 1 commit into
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Thumbnails decoded the source page at full resolution before downscaling, so a first page holding a high-resolution image could use hundreds of MB of heap and OOM the rendering pod. Enable PDFRenderer subsampling so the page is decoded near thumbnail resolution, and close the document afterwards.
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Jira: https://luceeserver.atlassian.net/browse/LDEV-6446
Problem
cfpdf action="thumbnail"renders the source page at full resolution before scaling it down to the thumbnail size. When the first page holds a high-resolution image, the full raster is decoded into heap first, so a single thumbnail request can use hundreds of MB and OOM the rendering process — even though the output is only ~140px.Change
In
PDFUtil.thumbnail(...):pdfRender.setSubsamplingAllowed(true)so PDFBox decodes the page near thumbnail resolution instead of decoding the full-size image and then downscaling.Measured effect
Rendering a 140px thumbnail of a page whose first page is a 6000×6000 image, under
-Xmx512m, using the same PDFBox 3.0.7 this extension depends on:~21× less heap, faster, identical thumbnail. A large file with a light first page was unaffected either way (+3.0 vs +3.2 MB), as expected — the cost scales with page-1 content, not file size.