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[claude] Retry a project download that loses the connection - #25

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fwlite-retry-dropped-download
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[claude] Retry a project download that loses the connection#25
myieye wants to merge 3 commits into
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fwlite-retry-dropped-download

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@myieye

@myieye myieye commented Aug 18, 2026

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[Claude, autonomous]

Staging PR — never merge; promoted to sillsdev when polished (see FORK.md).

A user's download failed twice in a row on Android: the wifi dipped for 7 seconds, the socket was aborted 24 seconds into the response, and both attempts threw away the whole download. The third try took 11 minutes and worked. The app's own connectivity watcher logged the network coming back 8 seconds after the first failure — well before the retry it never made.

Two changes, both in the download path only:

Known trade-off: ExecuteSync flattens "not signed in" and "no server configured" into the same unsynced result as "offline", so those permanent failures now spend 12s retrying before they report. Telling them apart means propagating SyncStatus out of ExecuteSync — a change to sync's public shape that doesn't belong in this PR. Flagged by both reviewers; deliberately left.

Follow-up this doesn't touch: a retry still restarts the whole transfer, because the download isn't paged or resumable.

A large project downloads in one request that can run for many minutes,
so a few seconds without connectivity throws all of it away: the
half-built project is deleted and the user starts over. Retry the sync a
couple of times before giving up, since connectivity is usually back
within seconds.

Also stop treating an unsynced result as a successful download; that path
leaves a project that says it downloaded but holds nothing (sillsdev#2292).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Review Change Stack

📝 Walkthrough

Walkthrough

Changes

The project download flow now retries selected connection failures and unsynced results. It invalidates cached server health between attempts and throws when synchronization remains unsuccessful. Tests cover the failure classification rules.

Project download retries

Layer / File(s) Summary
Download synchronization wiring
backend/FwLite/FwLiteShared/Projects/CombinedProjectsService.cs
CombinedProjectsService receives cache and logging dependencies. Project downloads pass the server and project name to DownloadChanges.
Retry policy and failure classification
backend/FwLite/FwLiteShared/Projects/CombinedProjectsService.cs, backend/FwLite/FwLiteShared.Tests/Projects/DownloadRetryTests.cs
Downloads retry after 2 and 10 seconds for unsynced results and recognized connection failures. Cached server health is invalidated between attempts. Connection classification and non-retry cases are tested.

Merge Risk: 🟡 Moderate · up to 0c8fd

The download retry path currently retries authentication or missing-server failures instead of failing immediately, causing unnecessary delays and incorrect retry behavior. This bounded correctness issue should be fixed before merging.

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myieye and others added 2 commits August 18, 2026 18:19
The first version only retried exceptions, but ExecuteSync reports most
ways of losing the connection as an unsynced result, and that was treated
as a permanent failure. So the second, longer retry never ran and an
outage of more than about two seconds still lost the download.

Retry the unsynced result too, and drop the cached server-health verdict
between attempts so the retry re-probes instead of being answered by the
check that ran while we were offline. Narrow the retryable exceptions to
socket failures: IOException also covers the sqlite writes made while
applying commits.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Await the download callback so it stays on the stack trace when it throws,
per the backend async convention. Loop over the delays instead of indexing
them, so the bound doesn't depend on the throw ordering. Retry a
HttpRequestException that carries no status code too: token refresh runs
before the sync's own offline handling, so its connection failures arrive
here raw, and no status code means no response ever came.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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myieye commented Aug 18, 2026

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Actionable comments posted: 1

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Inline comments:
In `@backend/FwLite/FwLiteShared/Projects/CombinedProjectsService.cs`:
- Around line 226-229: Update CombinedProjectsService’s retry flow and
SyncService.ExecuteSync to expose the unsynced failure reason, distinguishing
authentication or missing-server failures from connection failures. Retry only
connection-related unsynced results; return authentication-related failures
immediately without the existing delays. Add behavioral coverage for both
immediate authentication failure and retryable offline behavior.
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📒 Files selected for processing (2)
  • backend/FwLite/FwLiteShared.Tests/Projects/DownloadRetryTests.cs
  • backend/FwLite/FwLiteShared/Projects/CombinedProjectsService.cs

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Comment thread backend/FwLite/FwLiteShared/Projects/CombinedProjectsService.cs
@myieye

myieye commented Aug 18, 2026

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Closing: automatic retry isn't worth it. It's a band-aid for a download that isn't resumable, the user can already start one again the normal way, and the worst case silently re-spends a few hundred MB of someone's metered data. The real fix is making the download durable.

The one piece worth keeping — failing a download that never synced, instead of leaving an empty project (sillsdev#2292) — is now #26.

@myieye myieye closed this Aug 18, 2026
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