Templates and Hiera
In this lab we are going to replace the manual process of filling out the MediaWiki installation wizard, downloading LocalSettings.php and then uploading it back to the server. We will instead create a template file to dynamically fill in our settings file.
ERB Template
First we’re going to start off by replacing the following parameters in LocalSettings.php so they look like the following.
$wgSitename = "<%= @wikisitename %>";
$wgServer = "<%= @wikiserver %>";
$wgDBserver = "<%= @wikidbserver %>";
$wgDBname = "<%= @wikidbname %>";
$wgDBuser = "<%= @wikidbuser %>";
$wgDBpassword = "<%= @wikidbpassword %>";
$wgUpgradeKey = "<%= @wikiupgradekey %>";
Now that we’ve done that let’s copy the contents of LocalSettings.php file and paste it into /etc/puppetlabs/code/environments/production/modules/mediawiki/templates/LocalSettings.erb
You will need to create the templates directory.
Add the file resources to our init.pp so it looks like the following.
file { 'LocalSettings.php':
path => '/var/www/html/LocalSettings.php',
ensure => 'file',
content => template('mediawiki/LocalSettings.erb'),
}
After creating the template and the file resource we need to fill in all the variables with our specific values in nodes.pp
In our wiki node definition we need to add the following variables:
$wikisitename = 'wiki'
$wikiserver = "http://172.31.0.202"
$wikidbserver = 'localhost'
$wikidbname = 'wiki'
$wikidbuser = 'root'
$wikidbpassword = 'training'
$wikiupgradekey = 'puppet'
After filling in all the values log into the wiki server and run the puppet agent
Did it successfully run?
If so go ahead and load MediaWiki from the CentOS VM in your browser.
You should see a screen like this:
Improvements
MySQL
The process we used to install this included manual steps of walking through the installation wizard and then the values were put into LocalSettings.php, which we then converted to LocalSettings.erb.
MediaWiki created the database tables and structure within MySQL. If we tried to run this on a new node it would fail because the database structure and data does not exist.
This is something we could automate with Puppet by creating the database structure and populating it, however we are not going to do that right now.
Puppet will only created the LocalSettings.php file if we run Puppet. It will NOT create the database structure unless we add code to do that.
Hiera
Templates are great but they require us to create new variables and define their values for every single node. This can become extremely unwieldy, as we continue to expand and bring on new nodes. To fix this we are going to use Hiera to look at our data sources and pull out the info that is assigned to each node.
We are going to start by setting each of our required variables to search Hiera for the values.
In init.pp add the following to the top of the mediawiki class.
$wikimetanamespace = lookup('mediawiki::wikimetanamespace')
$wikisitename = lookup('mediawiki::wikisitename')
$wikiserver = lookup('mediawiki::wikiserver')
$wikidbserver = lookup('mediawiki::wikidbserver')
$wikidbname = lookup('mediawiki::wikidbname')
$wikidbuser = lookup('mediawiki::wikidbuser')
$wikidbpassword = lookup('mediawiki::wikidbpassword')
$wikiupgradekey = lookup('mediawiki::wikiupgradekey')
We are now going to edit our hiera.yaml file to specify where Hiera should look for configuration values.
Remember that by default Hiera looks in %{codedir}/environments/%{environment}/hiera.yaml so we need to update it with the following.
---
version: 5
defaults:
datadir: data
data_hash: yaml_data
hierarchy:
- name: "Per-node data (yaml version)"
path: "nodes/%{trusted.certname}.yaml"
- name: "Other YAML hierarchy levels"
paths:
- "wikidefault.yaml"
This tells Hiera to look for config values in %{datadir}/nodes/<node_name> and if it doesn’t match to fall back to %{datadir}/wikidefault.yaml
Now we need to populate these files. Let’s start with wiki.example.lab.yaml
Put the following in it.
---
classes:
- mediawiki
- linux
mediawiki::wikisitename: wiki
mediawiki::wikimetanamespace: Wiki
mediawiki::wikiserver: http://172.31.0.202
mediawiki::wikidbname: wiki
We are defining the values that are relevant to our wiki.example.lab node and also telling Hiera that it is part of the mediawiki and linux classes.
Now we need to put some values into wikitest.example.lab.yaml
Based on the values from above update this file making sure to change it to match wikitest.
---
classes:
- mediawiki
- linux
mediawiki::wikisitename: wikitest
mediawiki::wikimetanamespace: Wikitest
mediawiki::wikiserver: http://172.31.0.203
mediawiki::wikidbname: wikitest
Now go ahead and add following values to wikidefault.yaml
---
mediawiki::wikidbserver: localhost
mediawiki::wikidbuser: root
mediawiki::wikidbpassword: training
mediawiki::wikiupgradekey: puppet
Now that we’ve defined all of our values and setup the Hiera files we need to clean up our nodes.pp file
Start by deleting all the $wiki variables from the top of it.
$wikisitename
$wikimetanamespace
$wikidbserver
...
Now add the following to the wiki and wikitest node definitions.
This tells puppet to check the classes defined in our Hiera data files for values to our variables.
lookup('classes', Array[String], 'unique').include
Remove the following lines from nodes.pp for both wiki.example.lab and wikitest.example.lab
class {'linux':}
class {'mediawiki':}
Now that we’ve got all of our Hiera data files updated and our nodes.pp and init.pp are configured to point to Hiera we should test it and make sure all the values are returning successfully.
Using puppet lookup we can test each of the values and determine if they are being returned correctly.
Start by listing the classes that Hiera knows about.
sudo puppet lookup --environment production classes --node wikitest.example.lab
We have to specify the node because the wikidefault.yaml file doesn’t have any classes defined.
Now that we know it can see our classes let’s check the different variables. This will check the value for wikidbname in the mediawiki class. This can be replaced with any of the other defined variables, like wikidbuser, wikimetanamespace or wikisitename
sudo puppet lookup --environment production mediawiki::wikidbname --node wikitest.example.lab
Wiki (CentOS 6)
Log into the Wiki vm, run the puppet agent and confirm it completes successfully.
Wikitest (Ubuntu)
If you remember we have not actually gone through the Mediawiki installation wizard on this VM. We have to run through it manually first so that it populates the database with the values we need based on our Hiera configuration.
Visit the Wikitest site in your browser and run through the installation process, when you get to the MySQL settings page fill in following:
Database name: wikitest
Database username: root
Database password: training
Click Continue two more times
Fill in the following fields:
Name of wiki: wikitest
Your username: admin
Password: training
Password again: training
then click the radio button I'm bored already, just install the wiki and click Continue three more times, at this point it will prompt you to download the LocalSettings.php file but this isn’t required any more so just ignore that step.
Now log into the wikitest server and run the puppet agent.
After the agent completes go back and load the Wikitest site in your browser and you should see something like this:
