noitu/docs/deployment.md

Deployment

The whole game is one binary. It serves the WebSocket API, the built frontend, and its own health, readiness and version endpoints, and it reads a single database file at startup. The supported shape is the container image behind a reverse proxy that terminates TLS.

Configuration

Every setting is an environment variable and every one has a working default, so the image runs with nothing set.

Variable	Default	Meaning
NOITU_ADDR	:8080	Listen address
NOITU_DB_PATH	data/noitu.db	Derived dictionary, opened read-only at startup
NOITU_TURN_LIMIT	30s	Turn deadline, identical for bot and online games
NOITU_GRACE	30s	How long a disconnected player's seat is held for a reconnect
NOITU_ALLOWED_ORIGINS	(unset)	Comma-separated origin allowlist. Unset means same-origin only
NOITU_WEB_DIR	(unset)	Built frontend to serve. Unset serves the API alone
NOITU_TRUSTED_PROXIES	(unset)	Comma-separated proxy addresses or CIDRs whose X-Forwarded-For is believed. Unset keys limiters on the socket peer
NOITU_MAX_ROOMS	1000	Ceiling on live rooms across the process; a creator past it is told server_full
NOITU_MAX_CONNECTIONS	2000	Ceiling on open WebSockets; the next upgrade gets HTTP 503
NOITU_MAX_CONNECTIONS_PER_IP	0 (off)	Ceiling on open WebSockets from one address; the next upgrade from it gets HTTP 503
NOITU_DEBUG_ADDR	(unset)	Separate listen address for GET /debug/vars (expvar counters). Unset means the counters exist in the process but nothing serves them
NOITU_DRAIN_TIMEOUT	0s	How long a shutdown waits for live games to finish before ending them anyway; see "Draining on deploy" below

An invalid duration or count is logged and ignored rather than silently changing the rules of the game.

One timing is not configurable: an online room closes after 10 minutes in its lobby with no game started. It is a fixed constant because nothing about a deployment should change how long two people have to agree on a game, and a running game is bounded by the turn clock rather than by this. Chatting deliberately does not reset that window — talking is not playing, or a room could be held open for the life of the process by one message every nine minutes.

Chat's own bounds are fixed constants for the same reason: a room keeps its last 20 messages and one message is capped at 200 runes (server/internal/wsapi/room.go).

The image sets NOITU_ADDR, NOITU_DB_PATH and NOITU_WEB_DIR for you.

Origins

Leave NOITU_ALLOWED_ORIGINS unset when the binary serves the frontend, which is the normal case: the page and the socket share an origin and the browser's own check is enough. Set it only when the frontend is served from somewhere else, and then list exactly those origins. An allowlist that is wrong in the permissive direction lets any page open a socket as one of your players.

The image

docker build --build-arg VERSION="$(git describe --tags --always --dirty)" -t noitu:latest .
docker run -p 8080:8080 noitu:latest

make image runs the same build with VERSION filled in for you; see "Version" below.

The build turns the committed corpus, data/dictionary.txt, into the ~7 MB database the game uses in a builder stage, so it downloads nothing from Wikimedia. Only the database is copied into the final image. The result is a distroless image of about 25 MB running as a non-root user.

Version

GET /version answers with the build's version, and the same string opens the startup log line — the fastest way to confirm a deploy actually replaced the running process rather than restarted the old one. It comes from -X main.version=... at link time, populated from git describe --tags --always --dirty. make server runs that command directly; the Dockerfile cannot — .dockerignore deliberately keeps .git out of the build context, so a stale copy never ships in the image — so it takes the version as the VERSION build-arg instead, which make image supplies. Building the image directly with docker build . and no --build-arg VERSION=... reports dev, which is an honest answer for an unstamped build rather than a wrong one.

What travels with the data

The derived wordlist is CC BY-SA 4.0 while the code is Apache-2.0, so the image carries data/LICENSE, data/ATTRIBUTION.md, NOTICE and the Apache-2.0 LICENSE that NOTICE refers to. CI asserts all four are present, and that the upstream file is not. Removing them would put the image out of compliance.

The image does not carry a notice file for the third-party Go and JavaScript dependencies. That is accepted while the image is only built and run by the operator; it must be generated before an image is ever published or handed to someone else.

Behind a reverse proxy

The socket is a normal HTTP upgrade, but three settings are easy to get wrong and each one breaks the game in a way that looks like something else.

Forward the upgrade. Without Upgrade and Connection the handshake returns 400 or 502 and the page sits on "Đang kết nối…" forever.

Set a read timeout longer than the keepalive. The server pings every 20 seconds. A proxy that closes idle connections sooner will cut players off mid game, and it will look like a client bug because the server logs a clean close.

Turn response buffering off. A proxy that buffers will hold frames until it has enough to flush, which turns a 30-second turn into a guess.

nginx:

location /ws {
    proxy_pass http://127.0.0.1:8080;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_read_timeout 120s;
    proxy_send_timeout 120s;
    proxy_buffering off;
}

location / {
    proxy_pass http://127.0.0.1:8080;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

Caddy needs none of this: it forwards upgrades and streams by default.

noitu.example {
    reverse_proxy 127.0.0.1:8080
}

Coolify and Traefik

Coolify fronts every app with Traefik. With its default forwarded-headers settings Traefik discards any X-Forwarded-For the client sent and appends the real peer, so it is safe to trust. Left at the defaults of this server it is not trusted, and the whole player base shares one client address: one join bucket, and no way to switch the per-address connection cap on. Set these on the app's environment variables:

Variable	Value	What it changes
NOITU_TRUSTED_PROXIES	the subnet Traefik reaches the app on, for example 10.0.1.0/24	X-Forwarded-For is believed when the socket peer is inside this range, so join limiting and the per-address cap key on the real player. Find the range with docker network inspect coolify (or the app's own network, if Coolify put it on one) and use the narrowest CIDR that contains the Traefik container. Never a range the public can connect from
NOITU_MAX_CONNECTIONS_PER_IP	32 as a starting point	One address may hold at most this many open sockets. Off (0) by default because it is only meaningful once the address above is the real client; 32 leaves room for a household or campus NAT. Without it one host can hold every socket up to NOITU_MAX_CONNECTIONS
NOITU_DRAIN_TIMEOUT	below the container stop grace; see "Draining on deploy"	Live games get this long to finish on redeploy instead of ending at once

Variables take effect on the next deploy. An entry in NOITU_TRUSTED_PROXIES that does not parse is logged as a warning at startup and skipped, so read the startup log after redeploying; a range that is too narrow to contain Traefik fails quietly, back to one shared address.

If Cloudflare or another CDN sits in front of Traefik, Traefik itself must trust that CDN's ranges (forwardedHeaders.trustedIPs on the entrypoint), otherwise it overwrites the header with the CDN edge address and every player behind the same edge shares one bucket again.

To make Traefik stop routing to an instance that has started draining, give the service a load-balancer health check on /readyz through Coolify's custom labels: traefik.http.services.<service>.loadbalancer.healthcheck.path=/readyz and ...healthcheck.interval=5s, using the service name Coolify generated for the app (visible in the container's labels). Without it Traefik keeps sending new players to the old container until it is removed, and they are refused with server_restarting.

The client's own address

Rate limiting keys on the client's address, and by default that is the socket's own peer, RemoteAddr. X-Forwarded-For is attacker-controlled unless the proxy is known to append to it, so it is ignored until told otherwise. Behind a proxy every player therefore shares one bucket, which means one client brute-forcing room codes spends everybody's join budget.

The fix is to name the proxy. Set NOITU_TRUSTED_PROXIES to the address, or CIDR range, the proxy connects from — 127.0.0.1 for the nginx and Caddy examples above, or the container network's range under Compose — and the server walks X-Forwarded-For from the right, taking the first hop that is not itself a trusted proxy. Entries a client forged sit to the left of the one the proxy appended, so they are never reached. A peer that is not on the list is still keyed on its socket address, header or not.

Caddy appends the real client to X-Forwarded-For by default. nginx does not: without the proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for lines in the snippet above it passes the client's own header through untouched, and naming that proxy as trusted would let every client pick its own limiter key. Do not list a range the public can connect from either; that is the same as trusting the header unconditionally.

Capacity

Two ceilings bound the process as a whole, on top of the per-connection rate limits: NOITU_MAX_ROOMS live rooms and NOITU_MAX_CONNECTIONS open sockets. Past the first, creating a room answers server_full and the player is asked to wait; past the second, the upgrade itself is refused with HTTP 503 so the proxy can count it. Each connection also has a frame-rate ceiling, and a client past it is disconnected rather than throttled. The defaults are generous for one binary on a small host; lower them if memory is tight, because a room is a goroutine and an engine held for up to its idle window.

Neither ceiling can be held by one client alone. A socket that has not sent its Hello within ten seconds is closed, so an idle socket cannot sit on a connection slot, and the room-creation budget is charged to the client address as well as to the socket, so reconnecting does not refill it. The per-address budget is deliberately wide (a burst of 30, refilling at one room every two seconds), because without NOITU_TRUSTED_PROXIES every player behind the proxy shares it.

A third ceiling, NOITU_MAX_CONNECTIONS_PER_IP, bounds how many of those sockets one address may hold at once, and it is off by default. Turning it on is safe only once the client's own address (above) is the real one: behind a reverse proxy with NOITU_TRUSTED_PROXIES unset, every player shares the proxy's own address, and the cap would seat one of them and refuse the rest.

Observability

Set NOITU_DEBUG_ADDR to a second listen address — one that is not the one players reach, and never a public interface — to expose GET /debug/vars there: standard-library expvar, zero extra dependencies, a JSON object of process counters refreshed on every write. It is never mounted on the public address, unset or not, so leaving NOITU_DEBUG_ADDR unset is the same as not having it. Besides the counters below, expvar always publishes the process's full command line and its runtime memory statistics; that is the standard library's own doing, not something this server adds, and it is the whole reason /debug/vars lives on a separate address rather than a route on the public mux one config change could expose. In a container, binding it to 0.0.0.0 (:6060) makes it reachable from every other container on the same Docker network, which on Coolify can be the shared proxy network. Bind it to 127.0.0.1:6060, which only the container itself can reach, or leave it unset; do not put it on a wildcard address on a shared network. The counters, all prefixed noitu_: connections open and total; rooms live and total, each split bot/pvp; games started and finished the same way; words submitted, accepted, and rejected by reason; eliminations by reason; chat lines; join attempts refused, by whether it was the rate limit, an unknown code, or a full room; bot moves by difficulty; dead- end claims by whether the position actually had no legal move; words reported as real by ReportWord; resumes attempted versus succeeded; and word_rejected/word_reported log lines dropped by the process-wide rate limit on them (noitu_corpus_log_suppressed). None of it is read by the game itself — it is a second write next to a decision already made, not an input to one.

Every rejected word also gets one structured log line at Info, word_rejected, carrying reason, word, link (the syllable it had to start with), mode (bot/pvp) and room. word is never the raw text a player typed — it is normalized the same way the engine matches it (NFC, lowercase, single-spaced) and capped at 64 runes — so the line is safe to collect and is exactly the corpus-review question this project has open: which words players type that the dictionary does not have. Nothing else a player types is logged: not chat, not a nickname, not an accepted word.

A player who disputes a rejection this way — ReportWord — gets the same treatment: one Info line, word_reported, carrying word (normalized the same way), link (the syllable in play, empty when the report was not filed mid-game), mode (bot/pvp/none) and room. Only words of at least two syllables are recorded, and a session may file at most 20 distinct ones — never the player's nickname, on both counts for the same reason word_rejected never carries one. Between the two, this is the whole of the corpus dispute loop: triaged by hand today, into whatever curated word list eventually applies the fix.

Health and readiness

GET /healthz returns 200 once the dictionary has loaded, for the rest of the process's life. It does not report on live games, so it is a liveness check rather than a readiness one, and it never moves — a proxy or orchestrator using it to decide whether to kill the process must not see it fail during a drain, because the process is still correctly finishing the games it has.

curl -fsS https://noitu.example/healthz

GET /readyz is the readiness check: 200 while the server is accepting new rooms, 503 once it has started draining (see below). Point a load balancer's "stop sending me new traffic" check here and its "restart me" check at /healthz; pointing both at the same endpoint defeats the reason there are two.

The image has no curl or wget, so a container health check cannot shell out to one. The binary probes itself instead:

noitu-server -healthcheck

It sends GET /healthz to NOITU_ADDR (a bare :8080, or a wildcard host, is dialled on 127.0.0.1), and exits 0 on a 200 and 1 on anything else, printing the reason to stderr. The Dockerfile's HEALTHCHECK runs it every 30 seconds with a 10-second start period. It is a liveness check, so it deliberately does not follow /readyz into a drain.

On Coolify, leave the dashboard's own HTTP health check switched off: it executes curl or wget inside the container and cannot pass against this image. Coolify picks the health check up from the Dockerfile after the next deploy (the application then reports a custom health check found), and a rolling update waits for the new container to be healthy before it removes the old one. Confirm that in the deployment log after the first deploy.

A post-deploy check worth having beyond either is a real socket open, because both health checks pass whether or not the proxy forwards upgrades. Opening the site and starting a game against the bot is the shortest version of that.

Draining on deploy

Rooms are in memory, so a restart has always ended every live game — but a plain kill used to do that the instant the signal arrived, which is why "deploy when the game is quiet" was the only advice this document had. SIGTERM now runs a short sequence first:

1. The server stops accepting new rooms. A creator past this point is told server_restarting — the same UI key a live shutdown sends everyone else — rather than server_full, because unlike a full room this one is never coming back.
2. GET /readyz flips to 503, so a load balancer that checks it stops routing new players here.
3. The server waits up to NOITU_DRAIN_TIMEOUT for every room with a game actually running to finish on its own turn clock. A room sitting in its lobby does not count — it has no game a restart would cost, and waiting for one would make every deploy sit out somebody's abandoned tab.
4. Once every game has finished, or the timeout passes, every player still connected is told the server is restarting and the process shuts down as it always did.

After the notice goes out the process waits two more seconds, so the writes reach the sockets before it exits, then closes its listeners.

Each step logs the room and live-game count, so "did the deploy actually wait, and for what" is answered from the log rather than guessed at.

A second SIGTERM or SIGINT during a drain is not swallowed: the first signal hands signal handling back to the runtime, so a second one ends the process at once.

The container runtime, not this server, bounds the whole sequence. Docker sends SIGTERM, waits its stop grace period (10 seconds by default), then sends SIGKILL, which gives players no server_restarting notice and writes no final log line. The rule is

NOITU_DRAIN_TIMEOUT + 2s  <  container stop grace

so with Docker's default grace NOITU_DRAIN_TIMEOUT must stay at or below about 6s. A drain shorter than one turn only helps games in their last seconds; to let games ride out a full NOITU_TURN_LIMIT (30 seconds by default), raise the stop grace first, on Coolify wherever the application's container stop timeout is configured, and only then raise the drain timeout. If the grace cannot be raised, keep the drain short instead of letting the kill land mid-drain.

The default, NOITU_DRAIN_TIMEOUT=0s, is today's behaviour: nothing waits, every live game ends immediately. Setting it to something like 60s turns "deploy when the game is quiet" into "deploy whenever, and the games in flight get up to a minute to finish before they are cut off anyway" — the turn clock already bounds how long any one game can take, so a timeout a little over NOITU_TURN_LIMIT covers the common case of a handful of games mid-turn.

Resuming from a second tab

A resume token is a bearer credential: whoever presents a live one takes the seat, and the connection that held it before is closed. Opening the same game in a second tab, or reloading with the token still in localStorage, is therefore a takeover, not a copy — the newest connection to present the token wins the seat, on purpose. There is no liveness check on the connection being replaced beyond that; nothing here treats a second tab as an attack, because the token already proves it came from the same player. A future version that wants two tabs to share a seat, rather than fight over it, would need a different design — this one intentionally does not.

What a restart costs

A restart with NOITU_DRAIN_TIMEOUT unset, or a signal harder than SIGTERM, ends every live game immediately and tells players the server is restarting rather than leaving them waiting. There is no session persistence, by design, in this version — a game that does not finish inside the drain window is simply lost.

Updating the dictionary

The dictionary is committed as text, data/dictionary.txt, and the image is built from it, so the words a deploy ships are the words in the revision it deploys. The upstream dump is not pinned: dumps.wikimedia.org regenerates viwiktionary/latest/ monthly, and the corpus header records the SHA-256 of the dump it came from.

refresh-dictionary.yml downloads the current dump on the 10th of every month, or on demand from the Actions tab, regenerates the corpus and opens a pull request against dev. Merging it, and dev onward to main, deploys the new words like any other change. The pull request does not trigger CI, because GitHub does not run workflows on a pull request opened with GITHUB_TOKEN; the builder verifies the database before exporting the corpus, and CI runs again on the merge. GitHub disables scheduled workflows after 60 days without a commit to the repository, so re-enable it from the Actions tab if the pull requests stop.

To refresh by hand, run make fetch-dict and make refresh-dict, then commit data/dictionary.txt.

To change the source itself, update DICT_URL in the Makefile and the builder's constant (a test asserts the two agree), refresh the corpus, then record what changed in data/ATTRIBUTION.md.

Nothing migrates, because nothing persists.