Re: Adding a 'setup' phase to service startup?

[Stefan Karrmann <sk@mathematik.uni-ulm.de>]

My 2 cent:

Lars Kellogg-Stedman (Mon, Feb 21, 2005 at 05:41:59PM +0000):
> I was mulling over service dependencies yesterday, and I wonder if it would
> make sense to add a "setup" phase to runsv's service startup sequence.
> This would allow, for example, svwaitup to block while a service performed
> one time initialization.

You may use pipe-tools, cf.
<http://www.skarnet.org/software/pipe-tools/index.html>.

> Here I'm thinking particularly of long-running setup actions, such as
> database initialization or something.  The current solution -- waiting for
> a number of seconds and then crossing our fingers -- doesn't provide the
> level of control that runit provides in other areas.
> 
> This would make the start sequence look like this:
> 
>   IF file "setup" exists THEN
>     SET STATE TO S_SETUP
>     RUN file "setup"
>   END IF
> 
>   SET STATE TO S_RUN
>   RUN file "run"
> 
>   IF file "finish" exists THEN
>     SET STATE TO S_FINISH
>     RUN file "finish"
>   END IF

With pipe-tools you only need the run and finish file:

#########################
# run file
./setup
npt-notify ./events isup
standard-run-script

#########################
# finish file
npt-notify ./events down
#########################

The setup code my wait on another service X by ,npt-wait /service/X/events'.
The demon can even use libnptrigger to signal the events during its running.

Regards,
-- 
Stefan Karrmann