Defining the workgroup objectives

[Gerrit Pape]

On Sun, Jul 31, 2005 at 09:37:32PM +0200, a-aa wrote:
> I absolutly agree with that, but think about this.
> If you have 5 services, all of which depends on the "master" being up. 
> And that will try to connect to it's master at start.
> 
> How do you deal with that?  A solution like this for all of them?:
> 
> daemon --no-fork &
> while ls <file that indicates it's up, or netcat to see if port is
> open?>; do
>   sleep 1
> done
> fg 1
> 
> As executing them in order wont do anything.  You can't execute a daemon
> with --no-fork and expect it to be up a millisecond after, then anything
> depending on it has a high chance of failure.

The problem you're describing actually isn't a problem when using runit,
you should try it out.

On system boot all services are started up in parallel.  If services
depending on other services fail if the services they depend on are
not available, all is fine; due to the restart, they'll sort out
automatically.

For those special services that take a lot of resources before finding
out that they should fail, you can add a minimal test for the
dependency, but generally this shouldn't be necessary

 #!/bin/sh
 check-dependency || exit 1
 exec service-daemon

This also may be a workaround for services that don't detect a missing
service they depend on, but actually in this case the service daemon
should be fixed to fail in this case.

The advantage of this concept is that it not only works at boot-time,
but also on system's uptime and services failing unintentionally.
Furthermore in my opinion it's an quite easy solution to a rather
complex problem; keep it simple stupid.

Regards, Gerrit.
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