This Time Self-Hosted
dark mode light mode Search

Extending libdaemon

As Luca wrote, since I came home from the hospital I’ve been working quite a bit on LScube, in particular working on porting feng to use glib, which is a very interesting thing considering that it also allowed to reduce the dependencies (no more need for libgcrypt for instance, which was a problem to me since it didn’t use pkg-config and I find that a bit medieval nowadays).

One other thing that feng lacked was support for running as a daemon; as git-daemon shown recently, having proper support is much better than faking it through start-stop-daemon.

A proper support for running as a Unix daemon mean quite a few different things: proper logging to either stdout/stderr (when not running as daemon) or syslog (when running as daemon); pid file generation (a file, usually in /var/run, where the process ID of the running daemon is written); proper check for forking (so that the user is told if the daemon failed to start; check for if the daemon is running already if trying to execute it again on the same pid file (multiple instances, where allowed, should use multiple pid files); privilege dropping (you don’t want your daemons to run with root privileges, although the ones who provide network service might need those privileges at once to open privileged ports (below the 1024 boundary).

Implementing all these things can easily be a boring task considering that is almost the same for each daemon you might be writing (feng is not the only daemon in lscube). Luckily, someone already thought about this and started working on a solution: Lennart’s libdaemon, which he used for the Avahi daemon.

But as it happens, although libdaemon 0.12 (which is not even the latest version) already provides enough of the basics needed for feng, there are a few things that would require further wrapping around in the code of feng itself. This includes verbosity handling (you might not want to have information output on stdout/stderr; while with syslog you can easily configure your logging to reduce the output, on stdout/stderr you either implement verbosity or you get everything that is logged through the daemon_log() function), and privileges dropping.

The nice thing of working with good maintainers, though, is that they are open to suggestions and extensions, so thanks to Lennart availability, I started implementing those parts that I was lacking. Hopefully in a not-so-long time, there will be a new libdaemon release, which feng will use, that will provide all the needed functionalities.

I really like this approach since it allows to do the things right once and for all, upstream, without having to reinvent the wheel every time, especially considering that it’s not rare that, trying to reinvent the wheel, you get it -octarine- octagonal rather than round.

For those who would like to take a look at the work in progress of my extensions, you can find them on my git repository together with some autotools fixes and some patches for OpenSolaris compatibility.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.