if target blob already exists, migration will check the blob
if header is already with the targeted key (or no key if not ciphered) no need write
otherwise write the blob (that will convert any blob with no header into the correct version)
function read_dispatch:
the reader use th header to determined if file is encrypted
and which key (fingerprint) was used
if blob was recorded in legacy format (no header), it tries all attached keys on storage
last safety net: if none matched, do a blake3 on file, if it matches the file is
stored in clear (no cipher)
otherwise:
- blob is corrupted
- key is lost
Two chronic problems fall out:
1. **Split-brain config.** Admin edits DB via the panel; app boot ignores DB.
Migration completes; live backend hasn't moved. Admin has to remember to
copy env vars into `.env` and restart. Two sources of truth for the same
setting. Cutover is a manual multi-step flow; users routinely get it wrong.
2. **Migration data-loss window on concurrent writes.** The copy walks
`storage.blobs` in hash order. A blob whose hash is lex-lower than the
current cursor, written to source AFTER migration passed it, is never
copied to target. `passed=true, findings=0` completion does NOT guarantee
target has every blob. Silent.
3. **Migration target selection is fragile.** DTO passes the whole S3 config
at trigger time; secrets sit plaintext in `admin_settings`. Any future
pluggable-storage story compounds this (Azure, GCS, WebDAV-as-source, …).
This plan replaces the split-brain model with a single-source-of-truth
architecture:
- `.env` declares **N named storage entries** (immutable per-deploy).
- `admin_settings.storage.active_backend_name` holds ONE row — which named
entry the app currently runs on. That's the whole runtime config.
- Migration is the atomic transition from one active entry to another. Server
is put in read-only mode for the copy window; on completion, the active
pointer flips; a restart cuts over.
Edouard Vanbelle