Developing Plugins

Introduction

The plugins in Calyptos are implemented with the stevedore library. There are currently 3 different types of plugins:

We will go into more detail on each type of plugin below.

Validators

Validator plugins are meant to ensure that the configuration file provided will produce a functional Eucalyptus cloud when the deployer is run. The plugin has access to a ComponentDeployer object which provides:

  • Access to the configuration yaml
  • Methods for relaying success and failure messages
  • A dict that groups each machine in the deployment by their role/component

This step does not block you from continuing to deploy, however it is intended to provide feedback on configurations which we know will be suboptimal or simply non-functional.

The implemented plugins live in the eucadeploy/plugins/validator folder. Please add your validators there when submitting a pull request.

Below is an example of a very simple validation plugin. In this example plugin we will merely be checking that we have a CLC role defined and there is not more than 1 host in that group.

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 from eucadeploy.plugins.validator.validatorplugin import ValidatorPlugin

 class CLCCheck(ValidatorPlugin):
     def validate(self):
         if 'clc' in self.component_deployer.roles:
             self.success('Found at least 1 CLC')
             if len(self.component_deployer.roles['clc']) == 1:
                 self.success('Found only 1 CLC')
             else:
                 self.failure('Found more than 1 CLC')
         else:
             self.failure('No CLCs found')

Lets break down this plugin and note the interesting/crucial bits:

  • In lines 1 and 3, note that we must make our plugin inherit from the ValidatorPlugin base class
  • In line 4, each validator plugin must override the validate method, this is what will be called by the CLI
  • In line 5, we are grabbing the set of roles from the component_deployer, this is a dict of sets with each key being the name of the roles. Here we are simply checking that there exists a clc role
  • In lines 6 and 8, we log and report the success of our validations
  • In lines 10 and 12, we log and report the failure cases of our validations

In order to add our validator to the list of default plugins to run during the validation step we need to add it to the entry points found in the setup.py file. Validators belong in the eucadeploy.validator array. If example plugin was in the eucadeploy/plugins/validator/clccheck.py file we would add the following to the entrypoints:

'clccheck = eucadeploy.plugins.validator.clccheck:CLCCheck'

Debuggers

In order to install Calyptos you should run the following commands on a CentOS 6 host:

# yum install -y python-devel gcc git python-setuptools
# easy_install fabric PyYAML
# curl -L https://www.opscode.com/chef/install.sh | sudo bash -s -- -P chefdk
# git clone https://github.com/viglesiasce/euca-deploy
# cd euca-deploy
# python setup.py install

Deployers

In order to install Calyptos you should run the following commands on a CentOS 6 host:

# yum install -y python-devel gcc git python-setuptools
# easy_install fabric PyYAML
# curl -L https://www.opscode.com/chef/install.sh | sudo bash -s -- -P chefdk
# git clone https://github.com/viglesiasce/euca-deploy
# cd euca-deploy
# python setup.py install