vitrage-specs/specs/pike/template-not-operator-support.rst

Template not operator Support

We would like the templates language to support the "not" operator in addition to "and" and "or" operators.

Problem description

Today the templates language support the "and" and "or" operators, but this is not enough. Many scenarios can't be described by those two operators, and thus we would like to add a support for the "not" operator.

Proposed change

Remark: positive vertex = vertex that has an edge with "is_deleted"=False property.

negative vertex = the opposite of positive vertex. Meaning that the

vertex has only edges with "is_deleted"=True property.

The following changes needs to be done to support the "not" operator.

1. In the template validation. Check that the "Not" operator can appear only in the following way:

   "Not" operator can appear before edges.

2. Scenario Evaluator:

   check if "not" operator appears on an element, and add a property named "negative_condition" on it, and updated it's "is_delete" property to True.

3. Networkx Algorithm:

   In the subgraph_matching method. If the match is not a "negative condition" then perform regular subgraph_matching. Otherwise, if the match is a "negative condition" then perform subgraph_matching on a negative edges.

Performance/Scalability Impacts

The performance of the subgraph matching algorithm is a bit slower due to the steps above.

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

alexey_weyl <alexey.weyl@nokia.com>

Work Items

None

Future lifecycle

None

Dependencies

None

Testing

Added tests that are checking different uses of the "not" operator.

Documentation Impact

Added documentation in Vitrage:

https://github.com/openstack/vitrage/blob/master/doc/source/not_operator_support.rst

References

None