A cached source and its variants were served until eviction, so a
changed image at the same URL was never picked up.
After 24 hours a request checks the source with upstream, sending its
stored ETag and Last-Modified. A 304 renews the source with no download
or conversion. New bytes replace the source, and older variants are
converted again. A failed check serves the cached image and puts the
URL in the negative cache. This includes the full fetch made for a
variant whose source was evicted. Images not checked for 30 days are
evicted.
A variant file's modification time is its source's check time, so a
hit still makes no database call.
Model: opus-5-5
imgcache.FileStore is a directory of files named by a hex key, at
<ab>/<cd>/<key>. It writes a file under a temp name, syncs it and renames
it into place. It opens, reports the size of and deletes the file for a
key. The cache keeps its sources in one FileStore and its variants in
another, so ContentStorage and VariantStorage are gone. FileStore has no
Exists: the reconciliation pass checks a variant's file with Size, and the
tests look for the file on disk. Cache.Variant reads the content type from
the file's first bytes itself. storage.go is now filestore.go, and the
unused testdata/red.avif is gone.
Model: opus-5-5
clawbot