Re: [Xen-devel] [OSSTEST PATCH [RFC] 0/3] Series short description

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Dario Faggioli writes ("Re: [Xen-devel] [OSSTEST PATCH [RFC] 0/3] Series short 
description"):
> On gio, 2013-12-05 at 15:25 +0000, Ian Jackson wrote:
> > * You can't set up heterogeonous systems
>
> What do you mean with this?

I mean, you can't easily set up a mixed setup with a number of
different guest OS's, because each script only makes a particular kind
of guest.  If you wanted to do that you'd have to do it in sg-run-job -
and if you were going to write that then it could take care of the
whole problem.

> > > 2) given my limited perl skills, I though I better ask for
> > >    some early feedback. :-)
> > 
> > How's your Tcl ? :-)
> > 
> ... I knew a language called like that existed, but that is mostly it,
> and while I try to understand that fancy syntax, any pointer to what I
> should look at to understand how it "already knows how to parallelise
> operations on multiple hosts" and hence how I'd be able to "make it
> capable of doing these kind of stepwise operations on multiple guests"?

Tcl itself is just a programming language.  It happens to have very
good support for writing event-continuation-passing-style programs,
with little code.  (I also really like it.)

In sg-run-job the core of this is done with the spawn-ts and reap-ts
procedures.  Mostly in sg-run-job, these are combined into run-ts,
which spawns and then immediately reaps.

But there is an existing proc per-host-ts which interprets its
arguments as a specification of a set of hosts, and spawns the script
on each host and then reaps them again, so that the same script runs
in parallel on all the hosts.

This is used in the main run-job procedure for host installation, and
actually takes parallel effect in the paired migration tests.  But it
could be refactored to be slightly more general and then we could have
a similar per-guest-ts procedure.

The tcl.tk website has comprehensive language documentation of course,
but I would be happy to help/review/etc.  Do you like learning new
languages ... ?

Ian.

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