The server held one copy of the catalog, overwritten in place on every
push. When that copy was damaged there were two answers, both bad:
refuse to touch it for ever, which is what every device did for a week,
or overwrite it with ours, which loses whatever another device had
added since — the escape hatch of the previous commit.
A push now uploads to catalog.upload.sqlite, rotates catalog.sqlite to
.1 (and .1 to .2, .2 to .3, dropping the oldest), and moves the upload
into place. Rotation is server-side renames, oldest first so that every
destination is empty when it is written to — move_to refuses to
overwrite, by design — and a failure at any step leaves a gap in the
generations and never a missing current copy. The only transfer is the
upload itself.
A damaged current copy that arrived whole now merges from the newest
readable generation before ours goes over it, which loses nothing, and
is kept as .1 by the ordinary rotation rather than by a separate 40 MB
upload. NFR-R2 asks for the catalog to be backed up; this is the half
of it that lives with the copy other devices read.
dtourolle
2ce0fcc74a