Shachar, What you need is the functionality of a watchdog. HA clusters provide this functionality. Anyhow, I guess you don't have/need an HA cluster, so what you might want to look at is monit: http://mmonit.com/monit/ I understand that you want to monitor it using your own daemon, but I don't believe that you can reinvent the wheel in a reasonable time and effort, so I point you to Monit.
- Noam On Sun, Feb 1, 2009 at 3:42 PM, Shachar Shemesh <[email protected]> wrote: > Hi all, > > I've been bad. I know I have. This goes against any instinct that I have, > but I am failing to see a good reason WHY. > > The setup - I have an embedded system that is composed of several daemons. > The situation is that one of the daemons has to restart another daemon. The > restarted daemon (an SNMP agent) is outward facing, and therefor the time it > takes it to restart should be minimized, if possible. > > Then again, it is a daemon. It has no parent (well, init is its parent). I > can find it easily enough using its pid file, but I cannot get a > notification when it has actually quit. There is an option to add to the > SNMP the commands to send a notification to the other daemon when it exists, > but this has several disadvantages I will not go into right now. I can also > poll for the exit (i.e. - kill( pid, 0) every second until it says there is > no such process), but that adds latency until I begin the restart process. > > So what I did was to use ptrace. The controlling daemon connects to the > SNMP agent as a debugger, and this way gets notified with the usual "wait" > interface when the agent exits. I am not doing any fancy register > manipulation or any such stuff. > > Using ptrace as part of a production system feels wrong, but I cannot say > exactly why. The small amount of experimentation I did with this system, as > well as my extensive experience with ptrace when working on fakeroot-ng tell > me that the interface is stable enough. Still, it feels wrong. > > Any feedback would be welcome. > > Shachar > > _______________________________________________ > Linux-il mailing list > [email protected] > http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il >
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