Re: monit '-i' option - one new alternative and summary

[Jan-Henrik Haukeland]

Many good arguments, the one in 4) was especially clever. (I like the
way you think outside the box :) AFAIK, the solutions described in 2-4
replaces the need for the -i option. This means that we do not re-add
the -i option to monit, but instead add the solutions described below
to the monit man file and to the FAQ.txt. Do you have time to add the
text Martin? I suggest adding a short version to the INIT SUPPORT
section and a more verbose version (e.g. the text below) to the
FAQ.txt.


Martin <address@hidden> writes:

> Summary of currently known possible solutions:
>
> 1.) '-i' option
> ---------------
>
> Usage:
> - add following configuration to monitc (to start it in the case that it is 
> not
>   running):
>
>     check process myprocess with pidfile /var/run/myprocess.pid
>         start program = "/etc/init.d/myprocess start"
>         stop program = "/etc/init.d/myprocess stop"
>         alert address@hidden
>
> Advantage:
> - simple
>
> Disadvantage:
> - does not solve fundamental cause of the problem => the problem can still
>   occure regardless whether the service is slow starting or failed to start
> - the behavior is global for all monit services (sleep) - monit will not
>   monitor regardless whether the service is running or not
>
>
> 2.) start slow or critical service from monit directly
> ------------------------------------------------------
> Usage:
> - disable the service startup in appropriate or all runlevels. You can use
>   for example on RedHat:
>
>     chkconfig myprocess off
>
>   on Debian:
>
>     update-rc.d -f myprocess remove
>
>   general example:
>
>     mv /etc/rc2.d/S99myprocess /etc/rc2.d/s99myprocess
>
> - add following configuration to monitc:
>
>   check process myprocess with pidfile /var/run/myprocess.pid
>         start program = "/etc/init.d/myprocess start"
>         stop program = "/etc/init.d/myprocess stop"
>         alert address@hidden
>
> Advantage:
> - simple - the monit configuration is the same as in the case of -i option, 
> you
>   need only to disable the default startup
> - solves the problem cleanly - no race condition can occure, the service is
>   completely under monit's control (which is the case of -i option too - monit
>   takes over the responsibility for service, but after it was started from rc)
> - makes no sleep - services are started as fast as possible in the order as
>   configured in monit (+ dependency support) => monit starts monitoring as 
> soon
>   as possible
>
> Disadvantage:
> - the user must handover/reconfigure the startup responsibility (as outlined 
> above)
>
>
> 3.) wait for service to start in appropriate rc script
> ------------------------------------------------------
> Usage:
> - add following line to /etc/inittab behind rc:
>
>     id:2:initdefault:
>     ...
>     l2:2:wait:/etc/init.d/rc 2
>     ...
>     mo:2345:respawn:/usr/local/bin/monit -Iic /etc/monitrc # added line
>
> - add following configuration to monitc:
>
>   check process myprocess with pidfile /var/run/myprocess.pid
>         start program = "/etc/init.d/myprocess start"
>         stop program = "/etc/init.d/myprocess stop"
>         alert address@hidden
>
> - wait in the rc script of the service to start or sleep in it some time (to
>   pause the startup and hope that the service will be online in the meantime).
>
> Advantage:
> - per service - you need to care only for slow starting services
>
> Disadvantage:
> - it will pause the whole startup - init will not continue unless the service
>   will be online or fail or the sleep will finish
> - in the case that the startup failed, monit will detect it independently of
>   rc script (doppled control) => the fundamental cause can affect this 
> solution
>   too in the case that the service failed to start
>
>
> 4.) enable the service monitoring manualy
> -----------------------------------------
> Usage:
> - add following configuration to monitc:
>
>     check file myprocess.pid with path /var/run/myprocess.pid
>         if timestamp > 5 minutes then
>            exec "/usr/bin/monit -c /etc/monitrc monitor myprocess"
>
>     check process myprocess with pidfile /var/run/myprocess.pid
>         start program = "/etc/init.d/myprocess start"
>         stop program = "/etc/init.d/myprocess stop"
>         alert address@hidden
>         mode manual
>
>   This way you can enable monitoring after specified time since process 
> startup.
>   There should be allways pidfile which can be monitored - in the case that
>   myprocess is started from some sort of dispatcher and its pidfile will be
>   created later then monit starts, you can monitor the pidfile of such
>   dispatcher. In the case that this is not possible and there is no other
>   suitable file for timestamp monitoring, you can touch some file in the slow
>   service startup script (which is simple).
>
>
> Advantage:
> - per process - you need to do it for slow services only
> - based on already implemented features
>
>
> -----------
> Conslusion:
> -----------
>
> I think the solutions 2.) is the only clear solution (address the basic
> cause of the problem. Solution 4.) can be used as -i option alternative,
> it is based on present features and is per-process.
>
> Martin
>
>
>
>
>
>
> _______________________________________________
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>

-- 
Jan-Henrik Haukeland