The README claimed 2GB RAM as the minimum, but two background-processor
worker loops × sharp.concurrency(2) means up to four libvips threads can
decode full-resolution images in parallel — peak RSS lands at 1.5GB+ on
a batch of 20MP+ photos. Add Postgres + Redis + Node baseline and one
heavy batch on a 2GB VPS OOM-kills the backend, surfacing as 503s on
thumbnails until restart:unless-stopped brings it back. Reported in #602,
filed as #628.
Three changes, smallest-surface-area each:
1. backgroundProcessor.js — on startup, when UPLOAD_PROCESSOR_CONCURRENCY
is NOT set and os.totalmem() reports < 3GB, default to 1 instead of 2
and log a one-shot warning naming the override env var. Explicit env-var
setters keep their value. os.totalmem() reports container memory under
cgroup v2 so this works in Docker / k8s as well as bare metal.
2. README.md — bumped the documented minimum from 2GB to 4GB, kept 2GB
only as a "Low-memory hosts" recipe pointing at UPLOAD_PROCESSOR_CONCURRENCY=1
with the throughput trade-off spelled out. Added the 503-on-OOM symptom
so the next reporter finds it via search.
3. docker-compose.production.yml — commented mem_limit / memswap_limit
example on the backend service. Off by default (don't surprise existing
deployments) but visible to operators thinking about shared/multi-tenant
hosts. restart:unless-stopped already on every service.
No code path for memory-aware runtime throttling (Luca's option 4) — out
of scope for a bug fix; tracked separately if #1-#3 don't close the case.
Paul Nothaft
714a9f6fb1