[tor-bugs] #11016 [Tor]: Add support for systemd watchdog protocol

[Tor Bug Tracker & Wiki]

#11016: Add support for systemd watchdog protocol
-------------------------+---------------------
 Reporter:  misc         |          Owner:
     Type:  enhancement  |         Status:  new
 Priority:  minor        |      Milestone:
Component:  Tor          |        Version:
 Keywords:               |  Actual Points:
Parent ID:               |         Points:
-------------------------+---------------------
 Systemd provides a watchdog protocol, as described on
 http://0pointer.de/blog/projects/watchdog.html . It basically requires the
 service to write a message to a socket every X second, if some environment
 variables are set. While present since a long time, the newer v209 version
 provides a helper function to implement it, by moving the parsing logic in
 a library.

 So here is 2 patches for tor :

 The first one implement the Notify protocol for systemd, thus permitting
 people to use Type=notify in the systemd unit ( see
 http://www.freedesktop.org/software/systemd/man/systemd.service.html for
 the detail, as well as the rather lengthy debate on Debian init system for
 Jessie ). The patch is not doing much or adding much features, but I guess
 some people would prefer to have this Type of systemd unit rather than
 simple as it could prevent some race condition if a service requires tor
 to be really started and working, before being started himself. It also
 add status line to systemd, but that's not a feature that is currently
 used much ( I do hope maybe some higher level tool like cockpit would use
 it later ).

 The 2nd one is adding a event to the main loop to ping the watchdog on a
 regular basis, using the new function in libsystemd-daemon. So this way,
 if tor is stuck, it will be restarted. I guess I do not have to explain
 how and why this improve tor :)

 So far, I only have been able to test the first one on my Fedora 20 and I
 am waiting for package to test the 2nd one in real life. However, in order
 to release early, release often, I upload them here for review.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11016>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online