Refactor configuration templates in all cookbooks

URL of launchpad blueprint:

https://blueprints.launchpad.net/openstack-chef/+spec/refactor-configuration-templates

Problem description

Our templates for the configurations files for all services have grown through the years and it is getting harder and harder to figure out where to set a specific option that goes into the config files. The same is true for reading these configuration files after they have been rendered, since they contain a lot more options and code than actually needed or used. Additionally every time one of the OpenStack service projects adds or removes an configuration option, we manually need to add an attribute, some conditions and an entry in the template for this. Same goes for every change in the defaults, that is either not reflected at all in our config files, or set explicitly to the same thing, which is just unneeded code after all. Finally, the fact that all of our templates are quite big blocks of code and even contain some hardcoded values for specific configuration options, which came from the original configuration files imported years ago, does not help with keeping up with the multiple changes in the service projects.

Proposed change

The templates for OpenStack service configurations files should implement or use a logic of setting the needed key-value configuration options in the appropriate section automatically from properly defined chef attributes.

  • logic to render proper configuration files needs to be defined and added (example given below)
  • attributes used for or in configurations templates need to be checked and refactored to fit this logic
  • commonly used configuration options should be handled in one place
  • only needed configuration options should be set in the configuration files after rendering the template
  • configuration options that are specific to only a few setups should be removed from the default attributes and recipes (especially the switchcases for them) and moved to the documentation. Although this will mean to remove functionality in the sense of removing some switchcases and attributes in the original cookbooks, this should not mean to loose these completely, but rather move them to the documentation to allow an easy implementation in wrapper cookbooks.

Scope

This spec tries to define a refactoring process that implements a more elegant handling of template files for OpenStack service configurations throughout all cookbooks used to deploy OpenStack.

End user impact

  • Users of the cookbooks will be able to wrap all OpenStack chef cookbook more easily and set configuration options if needed without patching the actual templates.
  • Old wrapper cookbooks before this change will stop working partially and would need to be refactored accordingly. The same is true for all environment files that include configuration options for the services via attributes.
  • Reading configuration files will become a lot easier, since only specifically wanted and needed options will be included in them.
  • The user can add environment and company specific comments in the service configuration files via attributes.

Developer impact

Cookbook developers will not need to add attributes for configuration templates, nor should there be any need to change existing attributes to fit the changing defaults in OpenStack service projects. It should become easier to read the overall cookbook, since a big part of the code in the templates and attribute files will be cut or moved with this feature. Therefore it might be easier to contribute as a newcomer without spending hours to understand how all the attributes work with each other (given that the logic used to render the templates is easier to understand of course).

Implementation

Assignee(s)

Primary assignee:
<j-klare>

Other contributors:

Work Items

  • define a generic structure for templates, that can be used for most of the configuration files

  • main config files for services look like this for all configuration options:

    [section] # optional comment or description key = value (usually simple boolean, numeric or string) # optional comment or description key = [ array which could be large ]

  • create a logic to render configuration files from properly set chef attributes

  • attributes could look like this for main configuration files (e.g. nova or neutron.conf):

default['openstack'][service]['conf'][section][key] =
  value

without a comment:

default['openstack'][service]['conf'][section]['debug'] =
  true

with a comment:

default['openstack'][service]['conf'][section]['debug'] =
  { set_to: true, comment: 'this option is the switch to enable/disable debug loggging' }

cookbook-openstack-common/templates/common.conf.erb :

<% @service_config.each do |section, values| -%>
[<%= section %>]
  <% values.each do |key, value| -%>
    <% if value.class == Hash -%>
<%= "# {value['comment']}" -%>
<%= key %> = <%= value['set_to'] %>
    <% else -%>
<%= key %> = <%= value %>
    <% end -%>
  <% end -%>
<% end -%>

cookbook-openstack-compute/recipes/common.rb :

...
# activesupport currently needs to be upgraded, since the one used in
# chef 12 is too old (3.2.19) and does not include the needed deep_merge
chef_gem 'activesupport' do
  action :upgrade
  version '4.2.4'
end
require 'active_support'
...

neutron_admin_password = get_password 'service', 'openstack-network'
identity_admin_endpoint = admin_endpoint 'identity-admin'
identity_uri = identity_uri_transform(identity_admin_endpoint)
...

secrets = {
            neutron: {
              admin_password: neutron_admin_password,
              ...
            },
            keystone_authtoken: {
              identity_uri: identity_uri,
              ...
            },
            ...
          }

# merge node attributes with secrets like passwords etc. for
# usage in template['/etc/nova/nova.conf']
nova_config_options =
  node['openstack']['compute']['conf'].deep_merge(secrets)

template '/etc/nova/nova.conf' do
  source 'common.conf.erb'
  cookbook 'openstack-common'
  owner node['openstack']['compute']['user']
  group node['openstack']['compute']['group']
  mode 00640
  variables(
    service_config: nova_config_options
  )
end
...

cookbook-openstack-compute/templates/nova.conf.erb – not needed anymore

  • add a link to documentation/config reference to all config files
  • refactor currently used attributes to fit into that logic
  • adapt specs
  • define a set of minimal needed attributes to create a working stack and move the rest of the attributes into documentation
  • remove attributes that would set configuration options that are equal to the defaults
  • propagate not backward compatible change at a fitting point in time without making a lot of people angry

Testing

  • lint and style tests with rubocop (as is)
  • unit tests with chefspec with special focus on testing the proper rendering of the configuration templates (including the sections)
  • integration testing with chef provisioning

Documentation Impact

These patches should move a good part of the currently defined attributes to the documentation as examples for specific setups.

References