* fix(buzz): page a saturated history instead of skipping the oldest
buzz-relay serves at most RELAY_HISTORY_LIMIT (2000) stored events per
subscription, NEWEST-FIRST, even when the filter carries a `since`. A channel
that banked more than the cap across one disconnect therefore had its OLDEST
unread messages neither sent nor marked: the live page delivered the newest
2000, the watermark advanced past them, and the rest were lost -- the one
remaining path in this connector that could skip a message outright.
A chat/backlog page's EOSE now drives a descending `until` walk. When a page
comes back AT the cap it may have older matches held back, so the connector
re-asks with `until` set to that page's oldest `created_at` -- on a SEPARATE
`buzz-backlog-<uuid>` subscription id, never the live one -- and repeats until
a page comes back under the cap or reaches the `since` the live REQ was sent
with, bounded by MAX_BACKLOG_PAGES (50, warned when hit). Delivery is charged
to the subscription that carried it before any gate, so a page's saturation is
measured against what the relay sent, not what the allowlist/mention gates kept.
The walk is strictly additive: the live subscription, its filter, and the
watermark are never touched; a CLOSED for a backlog page only ends that walk;
re-opening the live subscription closes any superseded page rather than
orphaning it; and every failure simply leaves the pre-existing behaviour for the
next reconnect to retry.
* fix(buzz): skip the backlog walk when the channel has no read floor
Reviewer willem-bd noted the descending-until walk has no semantic stop when
`floor is None`: that is exactly a channel's first connect (no stored
watermark) and again after a MAX_CACHED_CHANNELS eviction of its cursor. On
those connects the walk would fetch up to MAX_BACKLOG_PAGES * RELAY_HISTORY_LIMIT
events per channel instead of the newest 2000 the connector used to take.
Require a floor before opening any backlog page. The backlog-loss case this walk
exists for always has a watermark (the cursor survives reconnects and restarts),
so it always has a floor; first connect and an evicted cursor keep the previous
behaviour. Covers the skip with a new test, retargets the page-bound test to a
real walk above its floor, and documents the floor requirement.
* fix(buzz): stop orphaned and stalled backlog walks
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
064bb50602