vitrage/doc/source/contributor/not_operator_support.rst

Templates Not Operator Support

Overview

The Templates language supports the "or" and "and" operators at the moment. Many scenarios can't be described by using only those two operators and thus we would like to add support for "not" operator as well.

Template Structure

The template is written in YAML language, with the following structure.

metadata:
  name: <unique template identifier>
  description: <what this template does>
definitions:
  entities:
      - entity: ...
      - entity: ...
  relationships:
      - relationship: ...
      - relationship: ...
scenarios:
    - scenario:
        condition: <if statement true do the action>
        actions:
            - action: ...

All the sections are in use as described in the "vitrage-template-format.rst" file. But in the condition section it will be possible to write the "not" operator in addition to the "and" and "or" operators. The "not" operator can be used only before a relationship expression.

Condition Format

The condition which needs to be met will be phrased using the entities and relationships previously defined. The condition details are described in the "vitrage-template-format.rst" and the addition here is the new logical operator "not":

• "not" - indicates that the expression must not be satisfied in order for the condition to be met.

The following are examples of valid expressions, where X, Y and Z are relationships:

• X
• X and Y
• X and Y and Z
• X and not Y
• X and not (Y or Z)
• X and not X

Supported Use Cases

Use Case 1:

There exists an instance on Host but there is no Alarm on the instance.

+--------+ +--------+ Not +---------+ | Host | ------> | Vm | < - - - - | Alarm | +--------+ +--------+ +---------+

metadata:
    name: no_alarm_on_instance_that_contained_in_host
    description: when host contains vm that has no alarm on it, show implications on the host
definitions:
    entities:
        - entity:
            category: ALARM
            type: instance_mem_performance_problem
            template_id: instance_alarm # some string
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance
    relationships:
        - relationship:
            source: instance_alarm
            target: instance
            relationship_type: on
            template_id : alarm_on_instance
        - relationship:
            source: host
            target: instance
            relationship_type: contains
            template_id : host_contains_instance
scenarios:
    - scenario:
        condition: host_contains_instance and not alarm_on_instance
        actions:
            - action:
               action_type: set_state
               properties:
                  state: available
               action_target:
                  target: host

Use Case 2:

There exists a host with no alarm.

+--------+ Not +---------+ | Host | < - - - - | Alarm | +--------+ +---------+

metadata:
    name: no_alarm_on_host
    description: when there is no alarm on the host, show implications on the host
definitions:
    entities:
        - entity:
            category: ALARM
            type: host_high_mem_load
            template_id: host_alarm # some string
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
    relationships:
        - relationship:
            source: host_alarm  # source and target from entities section
            target: host
            relationship_type: on
            template_id : alarm_on_host
scenarios:
    - scenario:
        condition: not alarm_on_host
        actions:
            - action:
               action_type: set_state
               properties:
                  state: available
               action_target:
                  target: instance

Use Case 3:

The Switch is attached to a Host that contains a Vm. The Switch is also comprised to a Network which has a Port. There is no edge between the Vm and the Port.

+---------+           +---------+
+----------- |  Host   | --------> |   Vm    |
|            +---------+           +---------+
|                                       |
v                                       |
+----------+                                 | N
|  Switch  |                                 | o
+----------+                                 | t
|                                       |
|                                       |
|                                       v
|            +---------+           +---------+
+----------> | Network | <-------- |  Port   |
+---------+           +---------+

::

metadata:
name: no_connection_between_vm_and_port
description: when there is no edge between the port and the vm, show implications on the instances
definitions:
entities:
- entity:
category: RESOURCE
type: nova.host
template_id: host
- entity:
category: RESOURCE
type: nova.instance
template_id: instance
- entity:
category: RESOURCE
type: switch
template_id: switch
- entity:
category: RESOURCE
type: neutron.network
template_id: network
- entity:
category: RESOURCE
type: neutron.port
template_id: port
relationships:
- relationship:
source: host
target: instance
relationship_type: contains
template_id : host_contains_instance
- relationship:
source: switch
target: host
relationship_type: connected
template_id : host_connected_switch
- relationship:
source: switch
target: network
relationship_type: has
template_id : switch_has_network
- relationship:
source: port
target: network
relationship_type: attached
template_id : port_attached_network
- relationship:
source: vm
target: port
relationship_type: connected
template_id : vm_connected_port
scenarios:
- scenario:
condition: host_contains_instance and host_connected_switch and switch_has_network and port_attached_network and not vm_connected_port
actions:
- action:
action_type: raise_alarm
properties:
   alarm_name: instance_mem_performance_problem
   severity: warning
action_target:
   target: instance

Unsupported Use Cases

Use Case 1:

There is a Host contains Vm, which has no edge ("connection") to a stack that has an alarm on it. Difference: The difference here from the graphs above, is that here there are two connected component subgraphs (the first is host contains vm, the second is alarm on stack), and the current mechanism doesn't support such a use case of not operator between many connected component subgraphs. In the subgraphs above, we had only one vertex which was not connected to the main connected component subgraph.

+---------+ +---------+ Not +---------+ +---------+ | Host | --------> | Vm | - - - - - -> | Stack | <--------- | Alarm | +---------+ +---------+ +---------+ +---------+

metadata:
    name: host_contains_vm_with_no_edge_to_stack_that_has_alarm_on_it
    description: when host contains vm without and edge to a stack that has no alarms, show implications on the instances
definitions:
    entities:
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance
        - entity:
            category: RESOURCE
            type: heat.stack
            template_id: stack
        - entity:
            category: ALARM
            type: stack_high_mem_load
            template_id: stack_alarm
    relationships:
        - relationship:
            source: host
            target: instance
            relationship_type: contains
            template_id : host_contains_instance
        - relationship:
            source: stack_alarm
            target: stack
            relationship_type: on
            template_id : alarm_on_stack
        - relationship:
            source: instance
            target: stack
            relationship_type: attached
            template_id : instance_attached_stack
scenarios:
    - scenario:
        condition: host_contains_instance and alarm_on_stack and not instance_attached_stack
        actions:
            - action:
               action_type: set_state
               properties:
                  state: available
               action_target:
                  target: instance