The first load of a gallery whose ?w= tiers do not exist yet could exit the Node
process — not 500 one tile, kill the backend. Two defects stacked.
The reader: LocalFsStorage.get() returns a lazy fs.createReadStream, so an ENOENT
arrives after the await returned and outside the route's try/catch. An unhandled
'error' event is a process-level throw. pipeStreamToResponse attaches the handler
the routes were missing — 404 for a vanished source, connection destroyed if
bytes are already on the wire, file headers cleared so the JSON error is not
served as image/jpeg or cached as a broken tile for an hour. Applied to all nine
streaming responses in gallery.js.
The writer: ensureThumbnailAtWidth passed regenerate:true, whose first act is to
DELETE the target — on a path only reached when the tier is absent. A grid fires
one request per tile, so one request unlinked the file another had just published
and handed to a reader. Without the flag the write is an atomic rename.
Generation is now also deduped per tier key: 8 concurrent requests ran 5 Sharp
passes before, 1 after.
Reported with a full diagnosis by @BraynArts.
Paul Nothaft
f735d26422