A HEIC was being decoded once per rung. av-club is stateless per request, so
seven rungs asked for from the original are seven ImageMagick conversions of it
— measured on fofos at 8.5 s each, against 1.1 s for the resize and encode that
follow. Six of the seven produced a pixel-identical intermediate and threw it
away: about 67 seconds per photograph where 16 would do, paid again on every
future upload.
So when av-club says a format needs converting, convert it ONCE into the staging
directory and cut every rung from that. `needsConversion` is asked rather than
guessed, because which formats are expensive is av-club's fact and a list of
them kept here would go on paying after its build stopped needing it. JPEG and
PNG are untouched — writing a full-resolution intermediate to save six cheap
reads would cost more than it saved.
Concurrency drops to one. Two was chosen to match av-club and is the right
number on a machine with room; fofos has 1.87 GiB of RAM, and two concurrent
12-megapixel decodes left 520 MiB free with 648 MB already paged out. The work
is CPU-bound on a box already at 99%, so the second worker was not buying
throughput — it was buying a second resident bitmap.
And the sharp calls now name their output format properly. `output` takes
`{ format, options }`; passing `{ webp: { … } }` was silently ignored, so
everything built before this encoded at sharp's default quality rather than the
82 asked for.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The mapping: derived/ mirrors originals/ directory for directory, and where
originals holds a FILE, derived holds a DIRECTORY of the same name — extension
included — with the renditions inside it. Keeping the extension is what makes it
total: a.jpg and a.png are different originals and must not share a folder. The
inverse is pure string work, so the filesystem is the record and there is no
second copy of the truth.
Images get a WebP ladder at 320/640/960/1280/1920/2560 plus full.webp, and
nothing is ever upscaled — a rung wider than the original would be a soft file
that srcset then confidently prefers over the sharp one. full.webp always
exists because for a HEIC it is the only browser-readable copy of the picture
there is.
Video gets av-club's web-1080 and web-720 presets by name, plus a poster. Images
are named by width because srcset descriptors are widths; video by height
because that is av-club's vocabulary and nobody misreads 1080.mp4.
The ladder is fixed here and the SITE chooses from it. This never reads
website/src/media/slots.ts — a plugin that knows a website's layout is a plugin
for one website, and that boundary is the difference between a template and
something fofos-shaped.
Each derived folder carries a manifest naming the size and mtime it was built
from, so the sync is idempotent and resumable: a run that died halfway is
finished by running it again. That is what makes an in-memory job acceptable
rather than merely convenient. It builds into <name>.partial and renames, so an
interruption can never leave a folder that looks finished.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
pastilhasandClaude Opus 5