On 4/24/2012 10:31 AM, Andy Taylor wrote:
Thank you very much for your detailed reply John. I hadn't looked at
Hiera before, it looks very interesting. On the point of it's not good
to include node/site data in manifests, it's kind of essential in my
eyes to the setup I am trying to implement.
At my company, one server may serve a site which has very different
requirements to another, so I really needed something that was very
flexible. To expand on the structure I outlined in my previous post:
each server has it's own node.pp file. If you need to change something
(e.g. MySQL settings, which will probably the most frequent one that
needs changing), you can simply edit that server's node manifest file.
The great advantage here is that each site's node manifest serves as
documentation of what changes have been made to it. It's also very
easy to read and understand for someone new to Puppet.
From some quick reading of the Hiera posts on the Puppet Labs blog, I
guess I could simply have a yaml file for each server with overrides
instead of doing it via the node manifest. However, I don't really see
the advantage of this approach, except for it would cut out some of
the clutter in my Puppet modules. The idea of a hierarchical set of
data being considered in line with Facter facts is very interesting
though, especially if I combined it with some custom facts of my own;
I will do some more reading on that.
With the class/definition point, I am wherever possible using classes,
as usually I'm dealing with the nature of a node (e.g. you are a
webserver, database server etc.) The only case I have used definitions
is for these configuration file overrides. So if I'm understanding
your comments on class/definition use properly, I think I'm sort of
taking the right approach to it...
The key concern for me at the moment is flexibility and scalability...
none of my stuff is live yet, and I want to make sure I'm using best
practices before I put it all in place. :)
Mr Bollinger did his usual excellent job of thoroughly explaining the
problem space in other parts of this thread. I'd simply add that using a
richer data store, such as Hiera, can keep you from doing complicated
gymnastics in your module code.
I'm using a hiera.yaml file similar to the following with fqdn at the
top and common at the bottom. I've added a role fact which is reading
/etc/role on the client. You can use any Facter fact such as %{domain}
or write your own. %{location} or %{datacenter} seems to be a common one
for admins with multiple sites.
:hierarchy:
- %{fqdn}
- %{role}_%{environment}
- %{role}
- %{environment}
- common
In my mysql::data class I add a variable and give it a default of 256M.
$innodb_buffer_pool_size = hiera('mysql_innodb_buffer_pool_size', '256M')
I can then set the following to deal with the specifics of my environment.
512M in my prod environment, production.yaml
4G in role db, db.yaml
1.5G on role db in environment stage, db_stage.yaml
8G on server db01.main.sfo, db01.main.sfo.mydomain.com.yaml
Going one step further you can use hiera_array to merge data. For
example you might allow a set of servers to monitor all servers and then
allow the local monitors as well. Assuming a location fact and the
following data files
common.yaml
monitoring_hosts:
- 'mon01.ord'
- 'mon02.ord'
lax.yaml
monitoring_hosts:
- 'mon01.lax'
class someclass::data {
$hosts = hiera_array('monitoring_hosts')
}
someclass::data::hosts = ['mon01.lax','mon01.ord','mon02.ord']
Hopefully this should give you some ideas of how to use Hiera in your
new system.
Ramin
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