Configure Arguments as Jinja Variables in Sample Task Scenarios

[Luke Short]

Only a few arguments in Rally sample task scenarios are set as Jinja variable. For consistency and flexibility it would be helpful for most, if not all, of the arguments be changed to Jinja template variables with a default value.

This Nova test has the "image_name" set as a variable at the top.

https://github.com/openstack/rally/blob/a9b88a5917ed3f23fa7411a1fd1998704c903a7e/samples/tasks/scenarios/nova/boot-and-show-server.yaml

{% set flavor_name = flavor_name or "m1.tiny" %}
{% set image_name = image_name or "^cirros.*-disk$" %}

This different Nova test does not.

https://github.com/openstack/rally/blob/a9b88a5917ed3f23fa7411a1fd1998704c903a7e/samples/tasks/scenarios/nova/boot-and-associate-floating-ip.yaml

{% set flavor_name = flavor_name or "m1.tiny" %}

If these arguments are changed into variables for every sample task scenario then it also becomes easier for Rally users to combine multiple sample scenarios and only have to supply one (or more) override variable with `--task-args` or `--task-args-file`.

It might even be ideal to set every value as a variable including runner, context, and sla sections.

[Boris Pavlovic (boris-42)]

I totally agree that current approach is far from ideal.

There are few things to take into account:

- Samples were not designed to be used without modifications ... (those are samples)

- We have already pre defined task to get key performance metrics from openstack https://github.com/openstack/rally/blob/master/tasks/openstack_metrics/task.yaml (and as you can see it's already support bunch of arguments)

- We are going to remove pretty soon samples, because we are working on "rally template" command that is going to allow to store templates in Rally database.

If you have time/will we can work together on template feature that is going to solve all problems above and way more...

[Luke Short (ekultails)]

Thank you for your feedback Boris. This is great news to hear. I would definitely love to talk more in detail about the future of Rally and how I could help contribute more. Is there a blueprint in Launchpad for the new "rally template" feature? I will be unavailable for the next week. After this week I will see if I can find you on the Rally IRC channel.

[Boris Pavlovic (boris-42)]

So we don't use actually blueprints;) and core team is quite small at the moment so we are trying to avoid bureaucracy, if you would like we can have short call and I can explain what we are working on and where help will be very appreciate, so you can pick whatever you are interested in ;)