No retry on 4xx, backoff on 5xx and transport failures, and a deadline on
every request. Before this, one transient 503 or TCP reset failed a file
for good, and a CDN connection that went quiet after accepting the request
blocked `quak backup` forever, because there was no timeout anywhere.
src/retry.ts holds the policy: a classifier that decides whether another
attempt could produce a different answer, and a loop that acts on it with
exponential backoff and full jitter. Retried: 5xx, 408, 429, transport
failures (the errno is read out of the cause chain, which is where Node's
fetch puts it), deadline aborts, and truncated transfers. Not retried:
every other 4xx, and anything unrecognised — a wrongly retried permanent
failure delays every remaining file, while a wrongly abandoned transient
one costs a single file the next run picks up. Attempt count, delays,
sleep and jitter source are all configurable through ApiClientOptions;
sleep being injectable is what lets the suite exercise the policy without
waiting.
Truncation needed a type before it could be classified. streamDecrypt
threw plain Errors whose messages began "download: stream truncated", and
classifying on message text would mean the next reword silently turned
every truncated download into a permanent failure. It now throws
TruncatedStreamError, which lives in src/errors.ts alongside ApiError so
the classifier can recognise both without importing the modules that
import it; api/client.ts re-exports ApiError, so it stays one class and
every existing import path still resolves.
Downloads retry the request, the stream consumption and the decryption
together. Only the first of those happens inside ApiClient: a socket
reset after the headers arrived throws in streamDecrypt, and retrying the
request alone would never see it. The client's own retry is switched off
for those two calls so the budgets do not multiply into sixteen requests
per file, and the atomic write stays outside the loop so a download that
took three attempts still performs one write and one rename.
Non-idempotent requests are not blindly replayed. postJSON and putJSON
reach create-session, two-factor/verify — which burns one of a few
second-factor attempts — and files/thumbnail, so they retry only when the
connection was never established and the server provably never saw the
request. putFile is exempt and retries fully: a presigned PUT stores one
whole object at one key, with no partial state to damage. It now throws
ApiError with the status, as do the two null-body paths, which previously
threw bare Errors that nothing could classify.
Timeouts come from AbortSignal.timeout(), renewed per attempt: 30s for
JSON and upload calls, 10 minutes for file bodies, since a value short
enough to keep a hung API call from stalling a backup would cancel a
legitimate multi-gigabyte download. The download deadline is enforced
over the body rather than only the headers, by racing each read against
the signal, so the guarantee does not depend on the fetch implementation
tearing down a stream it already handed over.
listMissingThumbnails now separates a genuine 404 from an exhausted
retry. Its bare catch reported both as missing, which after this change
would have let a few minutes of 500s talk fix-missing-thumbnails into
regenerating and re-uploading thumbnails that were fine. runBackup and
runMetadataBackup are untouched: the retry sits below them and their
per-file resilience is unchanged.
Rework against review findings on the branch.
Test runtime (B1): the suite's cost was never the 4 MiB fixture, it was
filling that fixture from the CSPRNG. sodium.randombytes_buf goes through
the wasm wrapper a byte at a time and takes ~20s for 4 MiB, against ~108ms
to encrypt the same buffer. Fixture content is not load-bearing anywhere in
the file — only length and tag are — so payloads now come from a seeded LCG
instead, which also makes them deterministic and reproducible as the README
asks. A seeded generator rather than a constant fill, so a downloader that
reordered or repeated chunks would still be caught. make test goes from
over the 30s cap in script/test (it was failing outright, then rerunning
verbose) back to 8.96s, against 10.02s on main.
Atomic write coverage (B2): every failure the suite injected originated in
streamDecrypt, which runs before anything is written, so no test observed a
temp file existing or being cleaned up and the catch block in writeAtomic
was dead code. rename is now intercepted in the test file, which adds two
cases per entry point: one asserting the staged file exists at rename time
and is a sibling of the destination, and one failing the rename itself so
the cleanup path runs with a temp file genuinely on disk. Deleting
writeAtomic in favour of a plain writeFile now turns the suite red.
TAG_FINAL (M1): STREAM_TAG_FINAL was a hardcoded 3 plus a test to detect
drift. The premise was right — libsodium attaches its constants inside
ready.then(...), so an eager module-level read binds undefined — but a lazy
read works, and decryptBlob was doing exactly that before. Replaced with
streamTagFinal(), which reads the library's own value at call time. The
drift test is repurposed to pin the accessor against the tag observed on a
real final chunk, which fails if it is ever made eager again.
Partial trailing chunk (M2): a transfer that stopped mid-chunk surfaced as
"authentication failed", which reads as corruption and sends the user after
the wrong problem. A final chunk that arrived in full always authenticates,
so trailing bytes that do not are reported as the truncation they almost
always are, with the authentication failure kept as the error's cause.
Poly1305 cannot separate a partial chunk from a corrupt one, so the message
names both possibilities; a corrupt whole chunk mid-stream is still
reported as an authentication failure, and both are now tested.
The pre-existing test that wrote its output to the process working
directory, i.e. the repo root, now writes into the test's temp directory.
streamDecrypt discarded the secretstream tag, so a download cut short
by a dropped connection decrypted cleanly up to the last whole chunk
and was returned as a success. downloadFile and downloadThumbnail then
wrote straight to the destination, and runBackup skips any existing
non-empty file, so a truncated original was treated as complete on
every subsequent run and never repaired.
streamDecrypt now tracks the tag of each chunk it pulls and throws if
the stream ended on anything other than TAG_FINAL, or if the body
carried no chunks at all — Ente always emits at least one chunk, as
encryptBlob shows by producing a TAG_FINAL chunk even for zero-length
plaintext, so an empty body is a failed transfer rather than an empty
file. Both error messages say the stream was truncated.
Plaintext is now staged in a temporary sibling file (same directory,
so the rename cannot cross a filesystem boundary; random UUID suffix,
so concurrent downloads cannot collide) and renamed into place only
after the whole stream has decrypted and verified. On any error the
temporary file is removed and the original error is rethrown
unchanged, so a cleanup failure never masks the real diagnosis. A
failed download therefore leaves the destination exactly as it was.
Public signatures and the DownloadResult shape are unchanged.
The download layer keeps its no-direct-sodium-import shape: TAG_FINAL
is re-exported from src/crypto as STREAM_TAG_FINAL, which decryptBlob
now uses too. Also moves the pullStreamChunk doc comment off
decryptBlob, where it had been sitting.
Retry and backoff remain out of scope; they stay the Next Step in
TODO.md and are tracked separately.
downloadFile streams the encrypted body from the CDN, buffers it to
the 4 MiB + 17 encrypted chunk boundary, decrypts each chunk via
secretstream pull, and writes the concatenated plaintext to disk.
downloadThumbnail does the same for the thumbnail CDN.
4 unit tests (single-chunk, large single-chunk, filename fallback,
thumbnail) + live integration test that downloads a real 472 KB JPEG
from the dev account and verifies it lands on disk.
Uses mkdtempSync for temp directories (not manual timestamp paths).
4 tests: single-chunk download, metadata-title fallback filename,
multi-chunk stream (50-byte chunks to exercise the buffering/split
logic without allocating 4 MiB), and thumbnail download.
Tests encrypt payloads with sodium's secretstream push, serve them
from a mock fetch, and verify the decrypted file on disk.
