Each upstream host's semaphore now counts the fetches holding or waiting
for one of its slots, and is removed from hostSems when the last of them
gives its slot back or stops waiting, so a long-running pixad no longer
keeps one semaphore per host it ever fetched from.
VariantStorage.Delete removes the variant's .meta file too, a missing one
not being an error; DeleteWithMeta, which eviction called for that, is
gone.
Model: opus-5-5
Nothing bounded total in-flight work, so a burst of cache misses across
hosts could exhaust memory. Two settings now do: max_concurrent_processing
(default the CPUs Go uses) and upstream_connections (default 64, beside
the per-host limit). A request that finds either full waits up to 10
seconds, then gets 503; a slot is released on every path. No request
holds source bytes while it waits: a cached source is read only after
the processing slot is taken, and a fetched one only while it holds its
upstream connection. libvips runs one worker thread per image with its
operation cache off. Both waits count toward downstream_timeout, as the
README says.
Model: opus-5-5
clawbot