HLS sessions were keyed by the item, so a second account opening the same
film killed the first one's session; the displaced player reclaimed at its
playhead and evicted the other in turn. The registry is now keyed by
(viewer, rating_key), segment requests resolve by both, and the session
directory carries the viewer (the orphan sweep still recognises the older
shapes).
Only transcodes counted toward a cap, so remuxes — each a whole segmented
copy of the film on the scratch volume — were bounded by the library size.
Three bounds now apply after every start, each dropping the least recently
used: two sessions per account, the transcode cap, and a new admin knob,
plex_max_sessions (default 8), over every session. A superseded session
request returns at once, since it waits on the killed ffmpeg, so an account
cannot park more request workers than it may hold sessions.
The subtitle extractor's full-pass slots were global and minutes long each;
one account opening subtitles on film after film could hold them all. An
account may now hold three of the six, and still gets windows past that.
Two near-end checkpoints arrive together routinely (the 10 s tick and the
debounced seeked flush); both read "not watched" before writing and both
scrobbled, bumping Plex's viewCount twice. The transition is now decided by
the write: an insert that did not conflict, or an update conditional on the
old status.
The finish also popped the push-ordering entry that _resume_push_superseded
reads, so an older resume push still in flight could land at Plex after the
scrobble and revive a resume point on a watched item. It now stamps the
entry instead; the existing eviction bounds the map.
peter