Provide systemd unit files for all calamari daemons

[mbukatov]

This is a proposal to include systemd unit files for calamari daemons. Right now, calamari services are managed by supervisord instead.

Reasoning

Since both Fedora and Debian distributions (and their derivates, such as RHEL or Ubuntu) are using systemd now, it would make sense to add systemd unit files for calamari so that on such linux distributions, superviord configuration could be replaced with systemd one. This would mean simplification of service management and better integration with the rest of the daemons.

[ChristinaMeno]

I like this idea.

[tserong]

Something like this: SUSE@4412c44 although later I decided python-carbon really should provide the carbon-cache systemd unit (SUSE@94d4529). I didn't submit these upstream, because they were done as part of some work to get rid of the venv and install everything in FHS paths, which I never quite managed to get into a suitably generic shape :-/

[mbukatov]

@tserong That looks like a good start. Do you think you could create a pull request with just systemd unit files so that the calamari upstream could discuss the details further there?

[aalba6675]

With 1.4, there seems to be only one single process calamari-lite (hosting in-memory "carbon-cache", cthulhu and REST API). Seems it can be simplified to a single systemd unit.

[Unit]
Description=Ceph Calamari

[Service]
ExecStart=/opt/calamari/venv/bin/python /opt/calamari/venv/bin/calamari-lite

[Install]
WantedBy=multi-user.target