[Pacemaker] Managing resources - classes

[Andrew Beekhof]

On Thu, May 28, 2009 at 7:33 PM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> Hi,
>
> On Thu, May 28, 2009 at 03:59:49PM +0200, Andrew Beekhof wrote:
>> On Wed, May 27, 2009 at 4:22 PM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
>> > Hi,
>> >
>> > On Wed, May 27, 2009 at 08:42:06AM -0400, Eliot Gable wrote:
>> >> http://clusterlabs.org/wiki/Documentation
>> >>
>> >>
>> >> First, read this (probably ten times or so, since it won???t make complete sense and you will miss various details the first couple of times):
>> >>
>> >> http://clusterlabs.org/mediawiki/images/f/fb/Configuration_Explained.pdf
>> >>
>> >> Then, if you want to use the CLI, read this:
>> >>
>> >> http://clusterlabs.org/mediawiki/images/8/8d/Crm_cli.pdf
>> >>
>> >> Or check out any other links on that main documentation site.
>> >>
>> >> I strongly recommend you start out learning with the XML CIB
>> >> and then, if you want, move to the CLI. Everything makes much
>> >> more sense if you understand the XML stuff.
>> >
>> > I'll disagree here. The crm shell is there to let the vast
>> > majority of people start working with Pacemaker without having to
>> > read XML. And then also enable most of them never to think about
>> > XML. crm should be able to represent all cluster configurations
>> > without the XML scaffolding (and you won't miss much, it is
>> > horrible anyway).
>>
>> oi! :-)
>> its much better than it was in 0.6
>>
>> > In short, what would one gain by reading XML
>> > instead of the stripped crm representation?
>> >
>>
>> Without question the crm shell is the best tool for changing the configuration.
>>
>> I still find the stripped representation harder to read though - I
>> seem to have trouble finding and focusing on the bits i'm interested
>> in at the time.  But I've been starring at the full form for over 5
>> years now, so that may not be surprising :-)
>
> So, which part do you miss? :) Seriously, perhaps formatting
> could be improved or something. I'm always listening. And,
> frankly, I don't like the crm representation that much either,
> but couldn't think of any better way at the time. Still, what it
> makes it great for me is that I don't have to stare like a sheep
> at XML, it always gives me headache.

I was thinking about this some more... I think I finally figured out
the problem and possibly what to do about it.
(Although I just checked the latest crm output, and it looks like
you've already made some nice improvements).

The XML is usually read in "formatted" form, in that its indented.
The indenting helps to group elements so that one can focus on just
what is currently interesting - just the params, or ops, or whatever.

What I think is missing from the syntax is visual differentiation of
the shell's keywords (op, params, location, etc..).
Originally I thought of using color or a bold font (like most prompts
use), but that requires special characters and every shell does it
differently.  So ultimately that seems to cause more problems than it
solves.

How about displaying the keywords in ALLCAPS though?
Something like:

PRIMITIVE FencingChild stonith:external/ssh \
	PARAMS hostlist="c001n01 c001n02 c001n03 c001n04 c001n05 c001n06
c001n07 c001n08" livedangerously="yes" \
	OP monitor interval="120s" timeout="300" \
	OP start interval="0" timeout="180s" \
	OP stop interval="0" timeout="180s"

It wasn't bad to begin with, but it feels nicer now and is more
readable when it appears as a single line (which I also come across).

PRIMITIVE FencingChild stonith:external/ssh PARAMS hostlist="c001n01
... c001n08" livedangerously="yes" OP monitor interval="120s"
timeout="300" OP start interval="0" timeout="180s" OP stop
interval="0" timeout="180s"

Thoughts?  Would that be hard to implement?
On the parsing side, I guess it would "just" be a matter of doing the
python equivalent of strcasecmp().