Add Unix domain socket support.

[sysvinit]

Details in the commit message.

[cbix]

You might want to checkout my PR from a while ago (now conflicting, but I'll try to rebase it soon). The goal was also to allow unix sockets, but is based on systemd (which, according to your username, you probably don't use? 😜).

[sysvinit]

The box where I'm running prosody-filer is just a stock Debian box, so it does indeed have systemd ;). My only comment on #22 would be that it requires systemd-specific functionality in order to enable listening on Unix sockets, while adding an explicit option makes this a little more portable (both to non-systemd Linux machines, but also on BSD's etc).

[ThomasLeister]

@sysvinit and @cbix nice idea to enable socket support! Indeed I like the "general approach" here more. Is @sysvinit 's approach also compatible to systemd things? I haven't looked into the details, yet and I'm not very familiar with that topic.

[sysvinit]

systemd's socket activation functionality is very similar to the traditional Unix inetd(8) -- the supervisor opens and listens on a socket, and then only when connections arrive on that socket is a process started to handle that connection. That process can then tell if it's been "socket activated" by checking for the presence of an environment variable set by systemd, which indicates which file descriptor numbers correspond to the listening socket(s) which systemd had opened previously. This means the service isn't started until it receives a request, which might be an advantage in some circumstances.

My changes are compatible with systemd inasmuch as they don't do anything which conflicts with systemd; they just don't use any systemd-specific functionality. (As it happens I have more than one instance of prosody-filer running on my machine which handles XMPP uploads, which I manage using the systemd user unit below:

# prosody-filer@.service
[Unit]
Description=prosody external upload handler

[Service]
Type=simple
ExecStartPre=/bin/rm -f /srv/sites/molly/run/prosody-filer-%I.sock
ExecStart=/home/molly/bin/prosody-filer -config /home/molly/conf/prosody-filer-%I.toml

[Install]
WantedBy=default.target

)

[cbix]

@sysvinit I like your approach! And yes, it all works side by side, I'll just have to make some changes to my PR later.

Anyway it's a good idea to leave the choice to the user, I don't know if packagers are usually opinionated about systemd vs. "manually configured" network services, in case this project aims to eventually make it into distro repos.

Also, happy holidays! 🎅