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swarm-otel: let the collector write its socket dir, and probe every route through nginx

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This commit is contained in:
atlas 2026-10-24 21:12:35 +02:00 • committed by mara
commit 41bea3c6d9
3 changed files with 104 additions and 6 deletions
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30
nix/host-modules/swarm-otel.nix
View file

@ -697,12 +697,17 @@ in
# A collector that is up but not listening on a socket the gateway names
# answers every producer with a 502 and fails no unit. This one fails when
# any receiver socket refuses a connection for 30s, so the switch reports
# it. It runs as the gateway's user: a socket nginx cannot open fails too.
# Any HTTP status counts as accepted; only a failed connect is a failure.
# any receiver socket refuses a connection for 30s, or when the running
# nginx cannot reach one, so the switch reports it. It runs as the
# gateway's user: a socket nginx cannot open fails too. On the socket any
# HTTP status counts as accepted. Through nginx 000, 502 and 504 fail and
# every other status passes, a collector's 4xx included.
systemd.services.swarm-otel-sockets = {
description = "wait for every swarm collector receiver socket to accept a connection";
after = [ "container@${cfg.machine}.service" ];
after = [
"container@${cfg.machine}.service"
"nginx.service"
];
wants = [ "container@${cfg.machine}.service" ];
# Restarted with the container, so every start of the collector is
# checked and not only the first one after a boot.
@ -727,6 +732,19 @@ in
echo "no connection to $sock after 30s" >&2
exit 1
done
# The running nginx, not its config. `--resolve` pins the vhost to
# this host's gateway.
for route in ${lib.escapeShellArgs (lib.attrNames receiverSockets)}; do
for _ in $(seq 30); do
code=$(curl -sk --max-time 5 --resolve ${cfg.domain}:443:127.0.0.1 -o /dev/null -w '%{http_code}' \
"https://${cfg.domain}/$route/") || code=000
case $code in 000 | 502 | 504) ;; *) continue 2 ;; esac
sleep 1
done
echo "https://${cfg.domain}/$route/ answered $code after 30s" >&2
exit 1
done
'';
};
@ -1666,6 +1684,10 @@ in
# `0007` makes each socket `0770`: group nginx can connect.
SupplementaryGroups = [ socketGroup ];
UMask = "0007";
# `DynamicUser` forces `ProtectSystem=strict` over upstream's
# `full`, so `/run` is read-only in the unit and the socket
# directory's writable bind mount does not reach it.
ReadWritePaths = [ socketDir ];
# A socket left by a killed process would fail the next `bind`.
ExecStartPre = [ "${pkgs.coreutils}/bin/rm -f ${lib.escapeShellArgs allSockets}" ];
};

71
nix/module-eval/swarm-services-switch.nix
View file

@ -920,6 +920,77 @@ let
&& lib.elem "container@swarm-otel.service" u.partOf
&& lib.elem "multi-user.target" u.wantedBy;
}
{
# `DynamicUser` forces `ProtectSystem=strict`, which leaves `/run`
# read-only unless the path is in `ReadWritePaths`. The controls: the
# unit really is DynamicUser, and a copy without the path, or with some
# other path, is read-only.
name = "the collector unit can write the directory its receiver sockets are created in";
ok =
let
host = serviceContainersWithCi;
sc = host.containers.swarm-otel.config.systemd.services.opentelemetry-collector.serviceConfig;
s = host.containers.swarm-otel.config.services.opentelemetry-collector.settings;
socks = map (r: r.protocols.http.endpoint) (
lib.filter (r: (r.protocols.http.transport or null) == "unix") (lib.attrValues s.receivers)
);
writes =
c: sock:
let
strict = (c.DynamicUser or false) || (c.ProtectSystem or "no") == "strict";
dir = dirOf sock;
under = p: p == dir || lib.hasPrefix "${p}/" dir;
in
!strict || lib.any under (c.ReadWritePaths or [ ]);
in
socks != [ ]
&& sc.DynamicUser
&& lib.all (writes sc) socks
&& !(lib.any (writes (sc // { ReadWritePaths = [ ]; })) socks)
&& !(lib.any (writes (sc // { ReadWritePaths = [ "/var/lib/opentelemetry-collector" ]; })) socks);
}
{
# The probe loop names each gateway route, and the routes are read from
# the vhost, not from the receivers the probe is built from. A script
# missing one route, or treating 502 as a pass, is rejected.
name = "the readiness unit probes every collector route through the gateway";
ok =
let
host = serviceContainersWithCi;
otel = host.services.hyperhive.swarm.otel;
locs = host.services.nginx.virtualHosts.${otel.domain}.locations;
routes = lib.sort lib.lessThan (
map (l: lib.removeSuffix "/" (lib.removePrefix "/" l)) (
lib.filter (l: (locs.${l}.proxyPass or null) != null) (lib.attrNames locs)
)
);
lines = script: map (lib.removePrefix " ") (lib.splitString "\n" script);
probed =
script:
let
loop = lib.findFirst (l: lib.hasPrefix "for route in " l) "" (lines script);
in
lib.sort lib.lessThan (
lib.filter (w: w != "") (
lib.splitString " " (lib.removeSuffix "; do" (lib.removePrefix "for route in " loop))
)
);
verdict =
script:
probed script == routes
&& lib.hasInfix "--resolve ${otel.domain}:443:127.0.0.1" script
&& lib.hasInfix "https://${otel.domain}/$route/" script
&& lib.hasInfix "case $code in 000 | 502 | 504) ;;" script;
script = host.systemd.services.swarm-otel-sockets.script;
in
lib.length routes > 2
&& lib.elem "h1" routes
&& lib.elem "swarm-grafana" routes
&& verdict script
&& !verdict (lib.replaceStrings [ " swarm-grafana" ] [ "" ] script)
&& !verdict (lib.replaceStrings [ "000 | 502 | 504" ] [ "000 | 504" ] script)
&& !verdict (lib.replaceStrings [ "--resolve" ] [ "--noresolve" ] script);
}
{
# The DynamicUser layout keeps the history under /var/lib/private; the
# static user's StateDirectory is the plain path. The move runs as its