# The control plane as a systemd unit. One VM, systemd, binaries from CI — not Kubernetes: a tmctl
# child runs for HOURS and holds an exclusive lock on the book's files on the local disk, so any
# orchestrator that can move a pod mid-run is hostile to this workload (PLATFORM_DIRECTION §3).
#
# This unit is also the honest answer to PD-13, orphaned engine processes: every tmctl the service
# spawns lives in THIS unit's cgroup, so a restart or a crash of the platform cannot leave a
# translation running with nobody watching it. The supervisor's process group handles the ordinary
# stop; the cgroup handles the case where the supervisor is no longer there to ask.

[Unit]
Description=TextMachine control plane
After=network-online.target postgresql.service
Wants=network-online.target

[Service]
# Type=exec, not notify: the binary does not speak sd_notify, and claiming it does would make
# systemd wait for a readiness signal that never comes.
Type=exec
ExecStart=/usr/local/bin/tmplatformd
User=tmplatform
Group=tmplatform

# KillMode=mixed: SIGTERM to the main process only, so the platform runs its own drain and stops
# its children the way the engine expects; SIGKILL to everything left when the timeout runs out.
KillMode=mixed
KillSignal=SIGTERM
# Longer than the platform's own drain (15s) plus the engine's stop grace (30s), or systemd would
# SIGKILL a tmctl mid-shutdown and leave its project lock behind.
TimeoutStopSec=90
Restart=on-failure
RestartSec=5s

# Secrets as credentials, not as environment: an environment variable is visible in
# /proc/<pid>/environ and is inherited by every tmctl child. The config reads *_FILE first.
LoadCredential=dsn:/etc/tmplatform/dsn
LoadCredential=oidc_client_secret:/etc/tmplatform/oidc_client_secret
Environment=TM_PLATFORM_DSN_FILE=%d/dsn
Environment=TM_PLATFORM_OIDC_CLIENT_SECRET_FILE=%d/oidc_client_secret
EnvironmentFile=/etc/tmplatform/env

# Books live outside the repository and outside /var/lib by owner's decision (~/books); the unit
# gets the one directory it may write and nothing else.
ReadWritePaths=/srv/textmachine
StateDirectory=tmplatform

# Sandboxing. Free, and it bounds what a compromised process reaches.
ProtectSystem=strict
ProtectHome=yes
PrivateTmp=yes
PrivateDevices=yes
NoNewPrivileges=yes
ProtectKernelTunables=yes
ProtectKernelModules=yes
ProtectControlGroups=yes
RestrictSUIDSGID=yes
RestrictRealtime=yes
LockPersonality=yes
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX

# These bound the unit's CGROUP, and by the argument at the top of this file every tmctl the
# platform spawns lives in it. So they do not bound "the control plane" — they bound the control
# plane plus every run in flight, together (PD-55). Two consequences follow, and both are decided
# here rather than discovered in production:
#
#  1. The ceiling is sized as a machine backstop, not as a service bound. systemd.resource-control(5)
#     calls MemoryMax= "the last line of defense"; as a percentage it needs no knowledge of the box.
#     A 2G figure would have been a bound on the RUNS, and the OOM killer invoked inside the unit
#     picks the largest process — the engine, holding an exclusive lock on a book's files. That is
#     precisely the SIGKILL that TimeoutStopSec= above exists to avoid.
#  2. OOMPolicy is set explicitly. The system default is `stop`: one OOM-killed tmctl would take the
#     control plane and every other run down with it, then land the unit in oom-kill failed state for
#     Restart= to pick up. `continue` logs the kill and keeps the service running, so the supervisor
#     survives to observe the child's exit. (What it does with that exit is the worker's job and the
#     worker does not exist yet — nothing calls Settle today, PD-43.) OOMScoreAdjust= cannot help
#     here: it is inherited by the children, so it cannot tell the engine apart from the platform.
#
# Bounding ONE run is the worker's job when it exists — a transient scope per run, not a knob here.
MemoryMax=80%
OOMPolicy=continue
# Platform plus concurrent runs, each a Go process with a few dozen threads: room for roughly a
# dozen runs on one VM, which is more than a single box will carry.
TasksMax=512
LimitNOFILE=8192

[Install]
WantedBy=multi-user.target