[erlang-questions] erlang and systemd: how to combine without nif

[Max Lapshin]

While migrating to systemd from old good SysV init, I've found that it is a
very good idea to speak to this daemon and tell him that my software is
alive and ready.


systemd authors offer library for this (and I suppose that they want to see
these calls in POSIX and all other OS).

Petr Lemenkov together with other commiters have written wrapper around
this C library: https://github.com/systemd/erlang-sd_notify

I was completely against this idea, because I do not want to take nif
around library that makes a very simple call, so I've decided to write a
code that relies on protocol in this systemd library:


https://gist.github.com/maxlapshin/01773f0fca706acdcb4acb77d91d78bb

Just drop this file to your source, add systemd as a permanent worker for
keepalive to work and don't forget to call systemd:ready to commit start.


Service file may look like this:



[Unit]
Description=Retroview
After=network-online.target
Wants=network-online.target

[Service]
Environment=HOME=/var/lib/retroview
Environment=PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin
Environment=LANG=C
Environment=PROCNAME=retroview
Type=notify
User=root
Group=root
LimitNOFILE=102400
ExecStartPre=/bin/mkdir -p /var/lib/retroview
ExecStartPre=/bin/mkdir -p /var/log/retroview
ExecStart=/usr/bin/erl -p /opt/retroview/ebin -noinput -name
retroview@REDACTED -s retroview
Restart=on-failure
TimeoutStartSec=300s
WatchdogSec=120
WorkingDirectory=/opt/retroview
NotifyAccess=main

[Install]
WantedBy=multi-user.target
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