Advanced templating in Puppet

Posted: 2017-07-02 10:54:40 by Alasdair Keyes

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For my web servers I have a puppet class that takes a hostname and sets up all the elements required to create a hosting account including...

• System user
• Folder structure, logs folder, public_html etc.
• Nginx config
• PHP-FPM config
• Webalizer config

All the configs are very easily templated except for Nginx. My requirement for this class is that if I have a predefined Nginx config, that puppet should use that, otherwise generate a config from a default template.

This turned out to be a harder task than I anticipated, but I managed to find a solution which could be useful to others.

    $hostname = $title
    $username = $hostname
    $home = "/path/to/hosting/space/$hostname"

    $nginx_config = "/etc/nginx/sites-available/$hostname.conf"

    file { $nginx_config:
        ensure  => 'present',
        owner   => 'root',
        group   => 'root',
        mode    => 0644,
        content => inline_template(
            file(
                "<MODULENAME>/etc/nginx/static_site_files/$hostname.conf",
                "<MODULENAME>/etc/nginx/default_site_template.conf"
            )
        ),
        notify  => Service['nginx'],
    }

It's a bit of a messy solution as we are actually putting a template within the files/ folder. As an alternative you can use an absolute path for file() and put the template within the templates/ folder, but this gets a bit problematic if you change your absolute paths.

It works in the following way....

• If I have a known Nginx config for this site, I place the file into files/etc/nginx/static_site_files/$hostname.conf.
• If this file exists it is used and then passed into the inline_template() function. As this file is a straight Nginx config with no Puppet ERB template tags, it is dumped into the file on the Puppet client with no changes.
• If I haven't got a known config at the path specified and I want to use a default config, it loads the template from files/etc/nginx/default_site_template.conf, then passes it to inline_template which does the correct templating such as log paths, server_name etc.

This means new default sites can be created easily and then customisations are simple to implement.

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