A transient GET failure on a healthy endpoint could park the client on an
unreachable fallback (e.g. the server host's Docker bridge gateway, which
plex.tv advertises as a local connection) for a full connect timeout, failing
every request in flight during that window (log bbr90).
The cascade now probes each candidate with an unauthenticated /identity
request under the discovery-race budget and only switches when it answers as
the expected server, mirroring the Jellyfin trust gate. Unreachable-looking
private IPv4 candidates stay in the list — a client on the server host can
legitimately reach them, so reachability is probed, not inferred.
The Discover tab fanned out its whole request set twice on every cold
start and replayed slow rows on a shrinking timeout ladder, so a healthy
remote server produced anywhere from 4s to 15s of loading.
Measured against a remote Jellyfin server with four libraries, 24
interleaved cold-start samples per side:
requests 19 -> 9 payload 219 KB -> 94 KB
settled 5231ms -> 2502ms median, 13222ms -> 5927ms p95
Four independent causes:
- Retry policy. `Client.send` resolves on response headers, so the
connect budget covers the server's think time and a slow-but-alive
query raises `connectionTimeout`. Replaying it made the server re-run
the query with a shorter budget than the one it just missed; the
`[10s, 8s, 5s]` ladder turned an 11s answer into an empty row after
23s. Hub surfaces now get one whole-request deadline, retry only
immediate connection errors, and the deadline bounds the whole call
including the request still in flight.
- Request shape. `/Items/Latest` groups a TV library by series, so its
rows are Series folder dtos and `RecursiveItemCount`/`ChildCount` cost
a DB count each, per row. Hub rows now ask for `Overview` only; watch
state survives because Jellyfin derives `UserData.Played` from
`UnplayedItemCount` when the count fields are absent. `/Shows/NextUp`
sends `NextUpDateCutoff` to bound the server's series-key scan, and
`Thumb` leaves `EnableImageTypes` since nothing reads it. `UserData`
and `PremiereDate` leave the browse set: neither is an `ItemFields`
member, so the server dropped them anyway.
- Fan-out. Per-library hubs ran in batches of three separated by a
barrier, so one slow library stalled every library behind it. A
sliding window keeps the same peak concurrency without head-of-line
blocking. Concurrent `fetchLibraries` calls now share one `/Views`
instead of racing two identical round trips, Plex's global and music
hub legs start together, and Jellyfin gets Plex's pool tuning.
- Duplicate pass. `DiscoverScreen.initState` starts a load and the
online-entry hook asked for a full refresh on top of it, which
`CoalescedLoadCoordinator` correctly queued as a trailing pass. The
hook now calls `primeRefresh`, which rides along with a load already
in flight; profile switches still go through `fullRefresh`.
Refs #1784
edde746