I've used Daemontools to provide a simple and reliable way to supervise Unix services on my servers. It works well, but it requires a different way of thinking (The DJB Way) and some common complaints are:
- TAI64N based timestamps
- Doesn't store scripts under /etc/init.d (or (/usr/local)/etc/rc.d)
- Doesn't always work with scripts like apachectl. Some scripts need to be rewritten.
I remember that some similar "supervisor/watchdog" daemons were in the works about two years ago, but some were still a little rough around the edges.
If you have switched from Daemontools to something else, what did you choose and did it work well for you? Does RedHat or Ubuntu come with any process supervisor utilities by default?
Best Answer
Hrm, if you're using Ubuntu, their new init process, upstart, includes a level of process supervision. It can be used for your standard starting and stopping of services, a la SysV init scripts, and it can also monitor running applications and respawn them if they die.
You can also implement a poor man's process restarter via inittab, depending on what your needs are.
If you're primarily looking for something to keep an eye on a process, to make sure it's always running, and then restart it when it isn't, I've had great luck with restartd. Unfortunately, the only source for it that I know of is the Debian package. However, it's a very small and simple application, basically just a single .c and .h file, with a make file. Compiling it from the Debian source tarball on Red Hat is trivial (I even made an RPM of it at my previous job).
A final option I've heard of, but not used, is Supervisor. It looks like a promising tool, but restartd has worked well enough for me in the past, for what I needed, that I haven't yet bothered to play with it.