output-show for parameter accessing incorrect attribute returns 'null'

[Unmesh Gurjar]

Branch: master

Description:
For resources like ResourceGroup, the output parameters are not validated during stack creation (bug #1368039). When a stack has an output parameter which accesses an incorrect attribute of a ResourceGroup resource, the output-show command returns the string 'null'. Returning a 'null' value for an output parameter will convey incorrect information to the user. Instead, returning an error indicating the invalid attribute access would be helpful.

Scenario:
1. Create a stack (named 'mystack') using the attached template (which has an output accessing an incorrect attribute of resource OS::Nova::Server).
2. Upon completion of stack, issue the 'heat output-show mystack instance1_ip' and observe the output.

Actual result:
The text 'null' gets displayed.

Expected behavior:
The command should return an error indicating the incorrect attribute being accessed. As in this case, returning a 'null' would convey incorrect meaning that the server resource was not allocated an IP address.

[Steve Baker (steve-stevebaker)]

The problem is that some attributes appear dynamically later in the resource's life-cycle, so raising an error for an attribute which isn't there *yet* isn't appropriate.

[Unmesh Gurjar (unmesh-gurjar)]

I agree for such attributes we cannot raise an error. But in cases like this, where the output of GET stack (sample http://paste.openstack.org/show/110507/ ), where there is an 'output_error' present for an output attribute, it is conclusive of an incorrect attribute access. Therefore, we can raise an error in such scenario. Does it sound appropriate?

[Angus Salkeld (asalkeld)]

 {"output_value": null,
  "output_error": "The Referenced Attribute (0 PublicIp) is incorrect.",
  "description": "The IP address of first instance",
  "output_key": "instance1_ip"}

The "output_error" is only there when there is an error.
This seems good to me, what would you want to do differently?

[Unmesh Gurjar (unmesh-gurjar)]

I would want to tweak output-show to return the error (i.e. the message in output_error field ) instead of the 'null' value.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/123993

[Visnusaran Murugan (visnusaran-murugan)]

IMO, regardless of error or success message, output_value should hold them. There should be an additional error flag to determine how output_value is consumed.

[Thierry Carrez (ttx)]

python-heatclient is not released withe the integrated release, so removing tag

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/123993
Committed: https://git.openstack.org/cgit/openstack/python-heatclient/commit/?id=a2bb6c965f104810782eabb0ee7c0d357cfcb4c7
Submitter: Jenkins
Branch: master

commit a2bb6c965f104810782eabb0ee7c0d357cfcb4c7
Author: Unmesh Gurjar <email address hidden>
Date: Wed Sep 10 13:11:22 2014 +0530

    Fixed null str returned for incorrect parameter

    For resources like ResourceGroup, the output parameters are not
    validated during stack creation. When a stack has an output parameter
    which accesses an incorrect attribute of a resource, the output-show
    command returns the string 'null'.
    This fix instead returns an error indicating the incorrect attribute
    being accessed.

    Change-Id: I51eea4738bfefb35644a384ec6d4e9176c8f2e26
    Closes-bug: #1368041