Puppet users - Aug 2009 - Managing intermittently available resources...

G''day.  I have a problem that I don''t know the best way to
mesh with Puppet.

Specifically, we have a database active/passive fail-over cluster.  Access to
the database is *only* possible on the active machine, not on the passive
machine.

I would like to manage various database resources, including databases, users,
and embedded PL/SQL features, that are database level features: you *MUST*
connect to the database server to check, or modify, them.  Direct disk access
is not possible.


So, how do I best manage that via puppet?

If I just configure a "database" resource on both machines I get
problems,
since we are not easily able to access the database server on the passive
system.


I can, I suppose, have both systems connect to the virtual IP address that
always points at the active server, and do all their administration over the
network.

That should /mostly/ work, except that it will fall down if I add a new PS/SQL
feature that requires a package installed, and the passive machine runs before
the active one ... so adds the DBMS feature while the package is not yet
installed.


My best guess, right now, is that I need to write a function, or a fact, that
determines if we are the active or passive machine for a specific service[1],
and then only configure those features when we are active.

Comments?
         Daniel

Footnotes: 
[1]  ...and these machines have multiple HA services, which can run on either
     or both; machine 1 might be active with the database, but passive with
     some other service.

-- 
✣ Daniel Pittman            ✉ daniel@rimspace.net            ☎ +61 401 155 707
               ♽ made with 100 percent post-consumer electrons
   Looking for work?  Love Perl?  In Melbourne, Australia?  We are hiring.

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2009/8/10 Daniel Pittman <daniel@rimspace.net>:
> My best guess, right now, is that I need to write a function, or a fact,
that
> determines if we are the active or passive machine for a specific
service[1],
> and then only configure those features when we are active.
I''d probably write a set of facts, one for each HA service, and then
take it from there.  I''ve found it pretty straightforward to write
custom facts, not hugely more complicated than whatever the underlying
process is to get the data.

-- 
* Matt McLeod     | People can do the work,
* matt@boggle.org | so machines have time to think

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On Aug 10, 12:37 am, Matt McLeod <m...@boggle.org>
wrote:
> 2009/8/10 Daniel Pittman <dan...@rimspace.net>:
>
> > My best guess, right now, is that I need to write a function, or a
fact, that
> > determines if we are the active or passive machine for a specific
service[1],
> > and then only configure those features when we are active.
>
> I''d probably write a set of facts, one for each HA service, and
then
> take it from there.  I''ve found it pretty straightforward to write
> custom facts, not hugely more complicated than whatever the underlying
> process is to get the data.
Agreed.  You can use the same resource(s) across a group of nodes,
relying upon one or more custom facts to determine, per node, what
configuration details that resource ensures.  Custom facts can be very
easy to write, though a clever enough programmer can make them
arbitrarily difficult :-)

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