openstack/puppet-openstack-guide
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Class structure and dependencies

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Add a segment to the coding style about the preferred
class structure and our view on dependencies, keeping
the relationship between classes to a minimal.

Change-Id: Iaa779357bf65f206ed8ea012668bbd1b66c9260e
This commit is contained in:
Tobias Urdin
2018-11-29 00:48:27 +01:00
parent 78ac1291ef
commit 0450457fb3
1 changed files with 26 additions and 0 deletions
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doc/source/contributor/coding-style.rst
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@@ -47,6 +47,32 @@ Before adding new parameters or new classes, see if other modules
already implement them and keep consistent. See also our common libraries
`OpenStackLib <http://git.openstack.org/cgit/openstack/puppet-openstacklib/>`__
Class structure and dependencies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The structure of classes should be consistent between modules for common resources.
There should be as few include or require statements as possible unless absolutely
neccesary, such as in the case when backward compatibility is required.
This helps to prevent redeclaration problems and issues where consumers of the modules
are forced to place resources in the proper order in their manifests to not cause those
issues. We should strive towards not enforcing ordering of resources in code, if we have
to do that we should inform our users properly and fail early unless the condition is met.
Note that this is not about the runtime dependency chain of resources but about placement
of code that can cause redeclaration issues because we include a class in another and the
consumer specifying that class at the same time.
Classes should be used to logically split up the functionality of modules to not
place everything in the same place. For example in the ``puppet-cinder`` instead
of having ``cinder::nova_username`` which configures ``[nova]/username`` you should
instead supply the ``cinder::nova`` class that takes care of the whole ``nova`` config
section.
Same structure should be used for database, logging etc to not group up all the
configuration options in the init class of the modules. Examples of this is the
``<modules>::db```and ``<module>::logging`` classes we have today.
Config file defaults and parameters
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~