fabi e6aeaa0a8b docs(compose): the app CPU cap cannot separate compression from the request path ...

The comment read "CPU ceiling for the two image workers + ffmpeg poster
extraction", which describes a separation Docker cannot make: `compression.rs`
runs that work in `tokio::task::spawn_blocking` — same process, same cgroup as
every Axum handler — and `cpus`/`cpu_shares` are per-container.

What actually happens is worth knowing when sizing this box: `cpu.max` is
`120000 100000`, so two CPU-pegged blocking workers exhaust the 120 ms quota
after ~60 ms of each 100 ms period and the kernel freezes the WHOLE cgroup —
uploads, feed and SSE included — for the rest of it. Over a 100-photo burst
that is ~210 s during which every request can eat up to 40 ms of throttle.

The value stays at 1.2: an app that can take both cores starves Postgres, and
every request path goes through Postgres. A slightly stalled request beats a
starved database. The comment now says which knob actually shortens the
backlog (COMPRESSION_WORKER_CONCURRENCY) rather than implying this one does.

2026-08-12 23:11:57 +02:00

16 KiB

Raw Blame History

View Raw