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feat(deploy): prod OOM swap cushion + edge maintenance page
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Two prod-deploy hardening measures (owner-requested):

- Swap file (Ansible common role, swap_size=1G, vm.swappiness=10). The per-container
  memory caps enforce that one service can't eat all RAM, but they overcommit the
  1.9 GiB main host (~2.8 GiB of caps), so a simultaneous spike could hit the kernel
  OOM-killer (and it might pick postgres). A small swap absorbs the overshoot.
  Idempotent, builtin-only (no ansible.posix).

- Edge maintenance page. prod-deploy.sh raises a flag around the rolling swap /
  migration window that the caddy edge serves a static 503 "технические работы" page
  from (deploy/caddy/maintenance.html), for the user-facing routes only — /_gm
  (Grafana) stays reachable. Cleared on any exit (success, health failure + rollback,
  or error) by a shell trap so it can never stick on. The 503 carries Retry-After +
  an X-Scrabble-Maintenance marker so a follow-up SPA overlay can tell a planned
  window apart from a transient error (the static page only catches a fresh load; an
  in-session user needs the app-side overlay). Not zero-downtime — the single
  stateful backend still blips — but the window is graceful instead of raw 502s.

Verified: caddy validate; the gate 503s every non-/_gm path incl. the Connect/gRPC
edge and serves the page + markers; /_gm bypasses; toggling needs no reload
(per-request stat). Ansible --syntax-check + compose config (base+prod) pass.
This commit is contained in:
Ilia Denisov
2026-07-03 22:09:37 +02:00
parent 4b4dcab9b6
commit c8601c0115
7 changed files with 172 additions and 1 deletions
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deploy/ansible/group_vars/all.yml
+8
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@@ -19,3 +19,11 @@ scrabble_base_dir: /opt/scrabble
# the host's own containers (and any ad-hoc runs) rotate identically.
docker_log_max_size: "10m"
docker_log_max_file: "3"
# Swap file as an OOM cushion. The per-container memory caps (docker-compose.prod.yml)
# sum to more than the tight main host's RAM (2 vCPU / 1.9 GiB), so a simultaneous
# spike could otherwise hit the kernel OOM-killer and it might pick postgres. A small
# swap absorbs the overshoot; swappiness stays low so swap is a cushion, not a hot
# path (a slow service beats a killed one). Set swap_size to "0" to skip provisioning.
swap_size: "1G"
swap_swappiness: 10