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Hi Vitaly,

I agree with you that conditions can be useful in case of complicated
plugins, but
at the same time in case of simple cases it adds a huge amount of
complexity.
I would like to avoid forcing user to know about any conditions if he wants
to add several text fields on the UI.

I have several reasons why we shouldn't do that:
1. conditions are described with yet another language with it's own syntax
2. the language is not documented (solvable)
3. complicated interface will lead to a lot of bugs for the end user, and
it will be
    a Fuel team's problem
4. in case of several checkboxes you'll have to write a huge conditions with
    a lot of "and" statements and it'll be really easy to forget about some
of them

As result in simple cases plugin developer will have to specify the same
condition of every task in tasks.yaml file, add it to metadata.yaml.
If you add new checkbox, you should go through all of this files,
add "and lbaas:new_checkbox_name" statement.

Thanks,

On Thu, Nov 27, 2014 at 7:57 PM, Vitaly Kramskikh <vkramskikh at mirantis.com>
wrote:

> Folks,
>
> In the 6.0 release we'll support simple plugins for Fuel. The current
> architecture allows to create only very simple plugins and doesn't allow to
> "pluginize" complex features like Ceph, vCenter, etc. I'd like to propose
> some changes to make it possible. They are subtle enough and the plugin
> template still can be autogenerated by Fuel Plugin Builder. Here they are:
>
>
> https://github.com/vkramskikh/fuel-plugins/commit/1ddb166731fc4bf614f502b276eb136687cb20cf
>
>    1. environment_config.yaml should contain exact config which will be
>    mixed into cluster_attributes. No need to implicitly generate any controls
>    like it is done now.
>    2. metadata.yaml should also contain "is_removable" field. This field
>    is needed to determine whether it is possible to remove installed plugin.
>    It is impossible to remove plugins in the current implementation. This
>    field should contain an expression written in our DSL which we already use
>    in a few places. The LBaaS plugin also uses it to hide the checkbox if
>    Neutron is not used, so even simple plugins like this need to utilize it.
>    This field can also be autogenerated, for more complex plugins plugin
>    writer needs to fix it manually. For example, for Ceph it could look like
>    "settings:storage.volumes_ceph.value == false and
>    settings:storage.images_ceph.value == false".
>    3. For every task in tasks.yaml there should be added new "condition"
>    field with an expression which determines whether the task should be run.
>    In the current implementation tasks are always run for specified roles. For
>    example, vCenter plugin can have a few tasks with conditions like
>    "settings:common.libvirt_type.value == 'vcenter'" or
>    "settings:storage.volumes_vmdk.value == true". Also, AFAIU, similar
>    approach will be used in implementation of Granular Deployment feature.
>
> These simple changes will allow to write much more complex plugins. What
> do you think?
> --
> Vitaly Kramskikh,
> Software Engineer,
> Mirantis, Inc.
>
> _______________________________________________
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> OpenStack-dev at lists.openstack.org
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>
>
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