Phases 2 and 3 of plan/23-monitor.md. /api/summary adds: server online/MOTD/
version, players online with NMSR heads, registered-account count, disk free on
the world volume, backup freshness, join/leave history, and TPS.
Each tile has its own TTL cache and its own failure mode. A failed collector
keeps serving its last good value and reports the reason in a sibling *_err
field, so the page goes stale-with-a-warning rather than blank. The five
collectors refresh concurrently: sequentially, one request during an outage
would cost the sum of every timeout (~15s), and an outage is exactly when
someone is looking at this page. Measured with a dead dependency: 0.24s.
TPS needs RCON, so the monitor now holds RCON_PASSWORD. Read-only survives
because the allowlist is a compile-time constant and no HTTP input reaches a
command string — the UI cannot run commands because the server cannot be asked
to. The Source RCON client is implemented in-repo rather than added as a
dependency precisely to keep that property local and auditable.
Two things the real server corrected:
- `neoforge tps` prints "Overall: 20.000 TPS (0.357 ms/tick)", not the older
Forge "Mean tick time / Mean TPS" wording the plan assumed. main_test.go
pins the real captured output so a format change fails a test instead of
silently zeroing the tile.
- Rosters come from mc-status, which already holds the Drasl admin credentials
and exposes a sanitized list, so this container does not get a second copy.
Also fixes a phase-1 bug: the UI's level regex assumed itzg's console timestamp
([12:34:56]) but the file uses [01Aug2026 22:55:34.358], so every line was
classified INFO and the ERROR/WARN chips did nothing. It now matches on shape.
The container runs as root deliberately — /data is drwxr-x--- owned by uid 1000,
so a non-root user cannot traverse it and the tailer would silently read
nothing. The :ro mounts and absent port are what bound the damage.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Phase 1 of plan/23-monitor.md: a small Go service that tails the Minecraft
server's latest.log into an in-memory ring buffer and serves it to an embedded
single-page UI (autoscroll, substring/regex filter, level chips).
Read-only by construction — /data is mounted :ro, there is no mutating route,
and the container holds no credentials. It publishes NO port: caddy's
basic_auth vhost is the only way in, which is the point, since the service has
no auth of its own and the log carries player IPs, chat and admin commands.
Two non-obvious choices, both to avoid prod-only failures:
- Polling, not SSE. The chain is host nginx -> caddy -> app, and nginx buffers
proxied responses by default, so an EventSource would stall on cochi (whose
vhost is an untracked per-host file) and not reproduce locally. Delay was
accepted at design time, so polling is strictly better.
- The cursor is a sequence number, not a byte offset, and the tailer reopens on
inode change or size shrink. itzg rotates latest.log on every server restart,
i.e. every deploy — a naive tailer goes silent afterwards while still
answering HTTP 200. Verified against rotate, truncate, delete/recreate,
partial-line and ring-overflow cases.
MONITOR_ENABLED (on|off) gates both layers per host, mirroring FILES_BROWSE.
MONITOR_PASSWORD_HASH must be bcrypt AND single-quoted in .env: Compose
interpolates $-sequences in .env values, so a bare hash is silently mangled
($2a$14$abc... -> $$2a$$14...) and every login fails with no hint why.
Confirmed empirically, and it is the opposite of filestash, which needs $6$.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
oierandClaude Opus 5