tropopause

Simplify creating AWS CloudFormation templates. This is an attempt at code as infrastructure and taking advantage of the benefits of code, such as loose coupling, reuse, and abstraction.

Mission Statement

CloudFormation provides a vast array of options and combinations for your deployment. This can be overwhelming for beginners as well as encouraging either many cfn templates or few large cfn templates in them for advanced users. CloudFormation does provide an element of flow control in the form of mapping (Fn:FindInMap) and conditions (Fn::And, Fn::Equals, Fn::If, Fn::Not, and Fn::Or), but this becomes complex very quickly.

This library aims to abstract away the more complex and time consuming aspects of building cloudformation templates, in favour of more common architectures. Although there will be a certain amount of ideology in how I choose to draw the boundaries on 'common' architectures, I will endeavour to keep it extensible; encourage plugins; and always make the underlying troposphere objects accessible.

Assumptions

All instances will be contain in auto scaling groups of at least 1.
All instances used in the core (nat instances, openvpn, etc.) will use the plugin architecture. Eat your own dogfood, etc.

Plugins

Creating

In the spirit of loose coupling and reusable code, rather than defining what an instance is meant to be at run time, you should extend a class which has compute.Group in the parent hierarchy. What does this mean?

It means this is bad because you'll have to copy/paste code to create another wordpress compute group.

my_web_server = compute.Group(title='WordPress')
my_web_server.config().packages.update({
    'yum' : {
        'httpd' : [],
        'php' : [],
        'wordpress': []
    }
})
my_project.add_computegroup(my_web_server))

And this is good because you include the plugin in as many projects as you wish

# ~/.tropopause/plugins/mycompany.py
from tropopause.components import compute
class Wordpress(compute.Group):
    def __init__(self, **kwargs):
        # Set defaults
        self.php_log_level = None
        self.
        # Initialise Parent
        super().__init__(*kwargs)
        # Override/extend parent
        self.config().packages.update({
            'yum' : {
                'httpd' : [],
                'php' : [],
                'wordpress' : []
            }
        })
        
# myproject/build_cfn.py
with plugin_source:
    from mycompany import plugins
...
my_project.add_computegroup(plugins.Wordpress(
    php_log_level=2
))

Core plugins

Compute Groups

compute.Group objects are a wrapper for launch configs, and autoscaling groups. By wrapping every ami/instance in an autoscaling group, we encourage Highly Available and redundant architectures. You can create a specific type of ec2 instance (for example a Bastion host) simply be inheriting from this class.

from troposphere.components import compute
class WebServer(compute.Group):
    def __init__(self, **kwargs):
        super().__init__(*kwargs)