[Unit]
Description=LED Matrix Display Service
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
User=root
WorkingDirectory=__PROJECT_ROOT_DIR__
Environment=PYTHONDONTWRITEBYTECODE=1
# glibc gives each allocating thread its own malloc arena, up to 8 x CPU count,
# and an arena that has grown is never handed back to the OS. This process runs
# 9 threads on a 3-core Pi, so the ceiling is 24 arenas -- and a rig measured at
# 1030 MB resident held 23 large anonymous mappings on 64 MB-aligned addresses,
# 920 MB of them, while the live data it was actually holding (widest scroll
# strip seen: 35,746 x 64) accounts for roughly 15 MB. That gap is arena bloat,
# not leaked objects: RSS was flat across repeated sampling, not climbing.
#
# Capping the arenas trades a little allocator concurrency for a large amount of
# resident memory on a device that has neither to spare. 2 is the usual value;
# raise it if frame times regress.
Environment=MALLOC_ARENA_MAX=2
ExecStart=/usr/bin/python3 __PROJECT_ROOT_DIR__/run.py
# Restart=always, not on-failure: run.py exiting 0 (a clean shutdown path taken
# for a reason that no longer applies, e.g. a config reload) would otherwise leave
# the service stopped and the panel dark indefinitely, with systemd considering
# that a successful outcome and never bringing it back.
Restart=always
RestartSec=10
# Memory ceiling as a share of physical RAM, so one unit file suits a 512 MB
# Pi Zero 2 W and an 8 GB Pi 5 alike. This is a backstop, not a tuning knob: it
# turns "the board runs out of memory, stops being able to fork, and takes sshd
# and the panel down together until someone pulls the plug" into "this one
# service restarts".
#
# NOTE: Raspberry Pi firmware boots the kernel with cgroup_disable=memory, and
# systemd accepts this setting and then silently ignores it. Verify with:
#     grep memory /sys/fs/cgroup/cgroup.controllers
# If that prints nothing, add "cgroup_enable=memory cgroup_memory=1" to
# /boot/firmware/cmdline.txt (all on line 1) and reboot. first_time_install.sh
# does this for you.
MemoryMax=85%
StandardOutput=journal
StandardError=journal
SyslogIdentifier=ledmatrix
# Support for on-demand plugin filtering via environment variable
# The environment variable LEDMATRIX_ON_DEMAND_PLUGIN can be set via:
# sudo systemctl set-environment LEDMATRIX_ON_DEMAND_PLUGIN=<plugin_id>
# Or by using an EnvironmentFile (see below)
# EnvironmentFile=__PROJECT_ROOT_DIR__/config/on_demand_env.conf

[Install]
WantedBy=multi-user.target