Peter and Henrik, thanks for writing in.
Let me explain the scenario once. We use puppet 3 with Hiera for appX
application. But due to some internal issues (management, company policy),
the team which supports the application (Support-appX) do not have access
to Hiera and those who manages Hiera (Support-Hiera) refuses to update
Hiera parameters and instead has suggested a work around - to avoid Hiera
and to replace it with a webservice which essentially mimics Hiera.
1) Sample Webservice which returns host specific json hash
-----------------------------
from flask import abort
{
"hosts": [
{
"description": "host vm 1",
"done": false,
"id": 1,
"title": "xyz",
"role" : "agent"
},
{
"description": "host vm 2",
"done": false,
"id": 2,
"title": "abc",
"role" : "loadbalancer"
}
]}@app.route('/appX/hosts/<int:host_id>', methods=['GET'])def
get_host(host_id):
host = [host for host in hosts if host['id'] == host_id]
if len(host) == 0:
abort(404)
return jsonify({'host': host[0]})
So calling http://localhost:5000/appX/hosts/2
<http://localhost:5000/app/api/nodes/node_id>will return the following json
hash corresponding to host vm 2 (only representational)
{
"description": "host vm 2",
"done": false,
"id": 2,
"title": "abc",
"role" : "loadbalancer"
}
2) Create a puppet module with a function "get_host_hash" which essentially
returns the above json hash as in the following example :
(ruby example - this need to be replaced by a puppet function get_host_hash)
require 'net/http'
url = 'http://localhost:5000/appX/hosts/2
<http://localhost:5000/app/api/nodes/node_id>'
resp = Net::HTTP.get_response(URI.parse(url)) # get_response takes an URI object
return resp.body
3) Write a class to retrieve config for host
class new_appx_class {
$config = get_host_hash ($::hostname)
$role = $config['role']
#calls roll specific wrapper class that passes parameters to underlying
appx puppet classes
class { "appx::$role":
config => $config
}
}
4) Wrapper classes for different roles
class appx::loadbalancer($config) {
class {'lvs'::real_server':
param1 => $config['lvs::real_server']['param1']
paramx => $config['lvs::real_server']['paramx']
}
class appx::agent($config) {
class {'lvs'::agent':
param1 => $config['lvs::agent']['param1']
paramx => $config['lvs::agent']['paramx']
}
My doubt is about step 2. Whether it is possible to write a puppet function
get_host_hash to call the webservice.
Thanks and Regards,
Pearl
On Saturday, 11 June 2016 07:14:02 UTC+5:30, Henrik Lindberg wrote:
>
> On 10/06/16 17:53, Pearl Raj wrote:
> > I am trying to write a module containing a function that returns
> > parameters from a webservice
> > - http://localhost:5000/app/api/nodes/node_id. This function should
> > return a hash of configuration settings specific to that host. How do I
> > do this? I am using puppet 3.0.
> >
> > pseudo code is as follows
> >
> > new module.pp
> >
> > function get_config_from_host(host_id):
> > call http://localhost:5000/app/api/nodes/node_id and get the config
> > hash of host_id
> > return config hash
> >
> > I am new to puppet, so confused whether it is possible to do this in
> puppet
> >
> > [Purpose of this exercise is to replace hiera]
>
> In recent 4.x version of puppet, you can use "data in modules and
> environment" using the lookup function. It provides an alternative way
> of looking up data to hiera in that you can write a function (named
> mymodule::data() for a module, and environment::data() in an
> environment. Those functions can be written in the puppet language.
>
> You will still need a function that makes the http call and transforms
> the result back to a hash.
>
> BTW: You can certainly return a hash from a custom function.
>
> What you get with hiera (lookup in later versions of puppet) is also
> automatic data binding of class parameters. That kind of data injection
> is the recommended way to set parameters as it makes your code a lot
> cleaner and more flexible to control.
>
> If you just write an arbitrary function you miss out on the automatic
> data binding. If you instead wrap that into the data() function
> supported as a "backend" (data provider) for lookup you will get both
> things.
>
> - henrik
>
> >
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