valheim: wait for an empty server, notify on install and recovery

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
rope 2026-09-11 17:24:39 +01:00
parent 8312873c0d
commit 285ee1aaaf

View file

@ -1,14 +1,20 @@
# services/valheim-autoupdate.nix — restart the Valheim server only when Steam
# actually ships a new build.
# actually ships a new build, and only when nobody is playing.
#
# The Pelican egg already has AUTO_UPDATE=1, so steamcmd runs on every boot and
# a restart *is* the update. The missing half is knowing when to bother, which
# a plain nightly restart doesn't answer (it reboots players for nothing 364
# nights out of 365). So, hourly:
# a nightly restart doesn't answer (it reboots players for nothing 364 nights
# out of 365). So, hourly:
#
# 1. installed buildid <- steamapps/appmanifest_896660.acf in the server volume
# 2. latest buildid <- the container's own steamcmd, public branch
# 3. differ, nobody playing -> POST restart to the wings daemon API
# 3. same -> exit. differ -> wait for an empty server, then restart.
#
# Waiting is a 10s poll held inside this one invocation rather than a re-check
# on the next hourly tick, because when Valve ships a build Steam auto-updates
# the *clients* — so everyone not currently online is locked out by a network
# version mismatch until the server catches up. Waiting an extra hour after the
# last player leaves is the expensive case, so we don't.
#
# Why the wings API and not `docker restart`: the egg's stop command is ^C, so
# wings sends SIGINT and Valheim saves the world before exiting. docker's
@ -17,8 +23,7 @@
# nothing to rotate by hand.
#
# Valheim has no console, no RCON and no broadcast command, so players cannot be
# warned in-game — the only honest options are "restart on an empty server" or
# "kick people mid-raid". This does the former and pushes an ntfy note instead.
# warned in-game at all. ntfy gets the play-by-play instead.
{ config, lib, pkgs, ... }:
let
# Pelican server "hawk" (panel server id 3). Both the volume path and the
@ -26,6 +31,17 @@ let
serverUuid = "185008d8-8a04-4077-be78-63853dc06c0e";
steamAppId = "896660"; # valheim_server; 892970 is the client
gamePort = "25569";
# Valheim's Steam query port is always game port + 1, and wings publishes it
# on the LAN address, not localhost.
queryHost = "10.0.0.1";
queryPort = "25570";
# How long to keep waiting for a busy server before giving up and letting the
# next hourly tick start over. Long enough for a full evening of play.
maxWaitSeconds = "21600"; # 6h
# Boot budget after the restart: steamcmd pulls the update, then Valheim
# loads the world (~40s on top).
bootTries = "90"; # x10s = 15min
autoupdate = pkgs.writeShellScript "valheim-autoupdate" ''
set -uo pipefail
@ -34,12 +50,17 @@ let
appid=${steamAppId}
manifest=/var/lib/pelican/volumes/$uuid/steamapps/appmanifest_$appid.acf
wings_cfg=/etc/pelican/config.yml
state=/var/lib/valheim-autoupdate/announced
secret=/var/secrets/ntfy-url
reply=/run/valheim-autoupdate/a2s-reply
docker=${pkgs.docker}/bin/docker
awk=${pkgs.gawk}/bin/awk
curl=${pkgs.curl}/bin/curl
grep=${pkgs.gnugrep}/bin/grep
nc=${pkgs.netcat-openbsd}/bin/nc
sleep=${pkgs.coreutils}/bin/sleep
date=${pkgs.coreutils}/bin/date
timeout=${pkgs.coreutils}/bin/timeout
notify() { # body
[ -f "$secret" ] || return 0
@ -49,11 +70,35 @@ let
-d "$1" "$url" >/dev/null 2>&1 || true
}
running() {
[ "$($docker inspect -f '{{.State.Running}}' "$uuid" 2>/dev/null)" = "true" ]
}
# ponytail: UDP conntrack entries for the game port are the cheap stand-in
# for a player count — no A2S challenge handshake to parse. They linger
# ~2min past the last packet, so this reads as "played very recently",
# which errs toward leaving people alone. Upgrade path if that's ever too
# coarse: A2S_INFO the query port and read the players byte.
players_online() {
$grep -q "dport=${gamePort} " /proc/net/nf_conntrack 2>/dev/null
}
# The server browser's own liveness test: anything at all back from the
# query port means Valheim is up and joinable. The first reply is a Steam
# challenge, which is enough — no need to complete the handshake.
query_answers() {
printf '\xff\xff\xff\xffTSource Engine Query\x00' \
| $timeout 3 $nc -u -w2 ${queryHost} ${queryPort} > "$reply" 2>/dev/null || true
[ -s "$reply" ]
}
installed_build() { $awk -F'"' '/"buildid"/{print $4; exit}' "$manifest" 2>/dev/null; }
# Nothing to restart, and no steamcmd to ask — a stopped server updates
# itself whenever it next boots anyway.
[ "$($docker inspect -f '{{.State.Running}}' "$uuid" 2>/dev/null)" = "true" ] || exit 0
running || exit 0
installed=$($awk -F'"' '/"buildid"/{print $4; exit}' "$manifest" 2>/dev/null)
installed=$(installed_build)
latest=$($docker exec "$uuid" \
./steamcmd/steamcmd.sh +login anonymous +app_info_update 1 \
+app_info_print "$appid" +quit 2>/dev/null \
@ -65,21 +110,22 @@ let
case "$installed" in ""|*[!0-9]*) exit 0 ;; esac
[ "$installed" = "$latest" ] && exit 0
# ponytail: UDP conntrack entries for the game port are the cheap stand-in
# for a player count — no A2S challenge handshake to parse. They linger
# ~2min past the last packet, so this reads as "played very recently",
# which errs toward leaving people alone. Upgrade path if that's ever too
# coarse: query A2S_INFO on the query port (game port + 1) and read the
# players byte.
if ${pkgs.gnugrep}/bin/grep -q "dport=${gamePort} " /proc/net/nf_conntrack 2>/dev/null; then
if [ "$(${pkgs.coreutils}/bin/cat "$state" 2>/dev/null || true)" != "$latest" ]; then
notify "Valheim build $installed -> $latest is out. Someone is online, so the update waits until the server is empty."
${pkgs.coreutils}/bin/printf '%s' "$latest" > "$state"
fi
echo "valheim-autoupdate: $installed -> $latest available, players connected, deferring"
exit 0
if players_online; then
notify "Valheim build $installed -> $latest is out. Waiting for the server to empty before updating."
echo "valheim-autoupdate: $installed -> $latest available, players connected, waiting"
deadline=$(( $($date +%s) + ${maxWaitSeconds} ))
while players_online; do
if [ "$($date +%s)" -ge "$deadline" ]; then
echo "valheim-autoupdate: still busy after ${maxWaitSeconds}s, leaving it for the next run"
exit 0
fi
$sleep 10
done
fi
# It may have been stopped by hand while we waited.
running || exit 0
token=$($awk '/^token:/{print $2}' "$wings_cfg")
if [ -z "$token" ]; then
echo "valheim-autoupdate: no wings token in $wings_cfg, cannot restart" >&2
@ -87,16 +133,35 @@ let
fi
echo "valheim-autoupdate: $installed -> $latest, server empty, restarting"
if $curl -fsS --max-time 30 -X POST \
notify "Installing Valheim build $installed -> $latest. Server restarting now."
if ! $curl -fsS --max-time 30 -X POST \
-H "Authorization: Bearer $token" -H 'Content-Type: application/json' \
-d '{"action":"restart"}' \
"http://127.0.0.1:8443/api/servers/$uuid/power" >/dev/null; then
notify "Restarted for Valheim build $installed -> $latest."
${pkgs.coreutils}/bin/printf '%s' "$latest" > "$state"
else
notify "Valheim restart request failed — server left on build $installed."
echo "valheim-autoupdate: wings power request failed" >&2
exit 1
fi
# Done when the manifest shows a different build than we started on (proves
# steamcmd finished) *and* the query port answers (proves it's joinable).
# Compared against $installed rather than $latest so an even newer build
# landing mid-wait still counts as success.
i=0
while [ "$i" -lt ${bootTries} ]; do
i=$(( i + 1 ))
$sleep 10
now_build=$(installed_build)
[ -n "$now_build" ] && [ "$now_build" != "$installed" ] || continue
query_answers || continue
echo "valheim-autoupdate: back up on build $now_build"
notify "Valheim is back up on build $now_build."
exit 0
done
notify "Valheim restart for build $latest was sent, but it has not come back after 15 min. Check the panel."
echo "valheim-autoupdate: server did not come back in time" >&2
exit 1
'';
in
{
@ -107,9 +172,10 @@ in
serviceConfig = {
Type = "oneshot";
ExecStart = autoupdate;
StateDirectory = "valheim-autoupdate";
# steamcmd's app_info_update round-trip is the slow part (~1min worst case).
TimeoutStartSec = "5min";
RuntimeDirectory = "valheim-autoupdate";
# The script holds itself open while waiting for players to leave, so
# this is only a backstop above its own 6h deadline + boot budget.
TimeoutStartSec = "7h";
};
};
systemd.timers.valheim-autoupdate = {