[Unit]
Description=llmsnap — vLLM control plane (drives model units over D-Bus)
Documentation=https://github.com/napmany/llmsnap

# Only start once the configuration has been provided by the user.
ConditionPathExists=/etc/quadlets/vllm/llmsnap/config.yaml

# Build the image first; the system D-Bus bus must be up to reach systemd.
Wants=llmsnap-build.service network-online.target
After=llmsnap-build.service network-online.target dbus.service

# Start/stop this unit when the target is started/stopped.
PartOf=vllm.target

[Container]
ContainerName=llmsnap
Image=localhost/llmsnap:latest
AutoUpdate=local

# Run as the vllm user (uid 10032) and itix-svc group (gid 10000). User 10032 (vllm)
# is authorized by polkit to manage the vllm-*.service model units over the host D-Bus bus.
User=10032
Group=10000

# Host network: llmsnap must bind 127.0.0.1:8000 on the HOST (reached by Traefik,
# which runs Network=host) and reach each model on the host loopback
# (127.0.0.1:5801+, published by the model Quadlets). A bridged namespace would
# make 127.0.0.1 the container's own loopback, not the host's.
Network=host

# Drive the host systemd over the system D-Bus bus. polkit authorizes uid 8100
# for org.freedesktop.systemd1.manage-units on vllm-*.service ONLY.
Volume=/run/dbus/system_bus_socket:/run/dbus/system_bus_socket
Environment=DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket

# llmsnap configuration (read-only).
Volume=/etc/quadlets/vllm/llmsnap/config.yaml:/etc/llmsnap/config.yaml:ro,Z

# SELinux: a confined container is denied access to the host D-Bus socket
# (container_t -> system_dbusd_t). Disabling the label keeps the socket reachable
# without shipping a custom SELinux module. The privilege boundary is enforced by
# the non-root uid + the scoped polkit rule, not by SELinux confinement here.
SecurityLabelDisable=true

# Hardening: llmsnap is only an HTTP proxy + a D-Bus client. It needs no extra
# capabilities and no writable root filesystem.
NoNewPrivileges=true
DropCapability=ALL
ReadOnly=true
Tmpfs=/tmp

# `systemctl` (the model cmd:/cmdStop: in config.yaml) refuses to talk to the
# host manager unless sd_booted() succeeds, i.e. unless /run/systemd/system
# EXISTS in this mount namespace. With ReadOnly=true, Podman mounts a fresh empty
# tmpfs over /run, so that path is absent and every systemctl call aborts early
# with "System has not been booted with systemd (PID 1)" / EHOSTDOWN — *before*
# it ever tries the D-Bus socket. This empty tmpfs just makes the directory
# exist so the check passes; the actual start/stop/is-active still go over the
# mounted host system bus (DBUS_SYSTEM_BUS_ADDRESS), gated by the polkit rule.
Tmpfs=/run/systemd/system

# ENTRYPOINT is the llmsnap binary; these are its arguments.
Exec=--config /etc/llmsnap/config.yaml --listen 127.0.0.1:8000

[Service]
Restart=always
RestartSec=5
# Give in-flight model swaps time to settle on shutdown.
TimeoutStopSec=60

[Install]
# Start with the target (llmsnap is the control plane; the models are not).
WantedBy=vllm.target