# 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.

Note: This document refers to Vitrage templates version 3.

For previous versions, see:

Version_2

### Template Structure

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

    metadata:
      version: 3
      name: <unique template identifier>
      type: standard
      description: <what this template does>
    entities:
      example_host:
       type: nova.host
       name: compute-0-0
      example_instance:
       type: nova.instance
      example_alarm:
       type: zabbix
       name: memory threshold crossed
    scenarios:
      - condition: <if statement true do the actions>
        actions:
          ...

All the sections are in use as described in the “vitrage-templates.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:
>         version: 3
>         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
>     entities:
>         instance_alarm:
>             category: ALARM
>             name: instance_mem_performance_problem
>         host:
>             category: RESOURCE
>             type: nova.host
>         instance:
>             category: RESOURCE
>             type: nova.instance
>     scenarios:
>         - condition: host [contains] instance AND NOT instance_alarm [on] instance
>           actions:
>                - set_state:
>                    state: available
>                    target: instance

## Use Case 2:

There exists a host with no alarm.

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

>     metadata:
>         version: 3
>         name: no_alarm_on_host
>         description: when there is no alarm on the host, show implications on the host
>     entities:
>         host_alarm:
>             category: ALARM
>             name: host_high_mem_load
>         host:
>             category: RESOURCE
>             type: nova.host
>         instance:
>             category: RESOURCE
>             type: nova.instance
>     scenarios:
>         - condition:  not instance_alarm [on] instance
>           actions:
>                - set_state:
>                    state: available
>                    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:
           version: 3
           name: no_connection_between_vm_and_port
           description: when there is no edge between the port and the vm, show implications on the instances
       entities:
           host:
               category: RESOURCE
               type: nova.host
           instance:
               category: RESOURCE
               type: nova.instance
           switch:
               category: RESOURCE
               type: switch
           network:
               category: RESOURCE
               type: neutron.network
           port:
               category: RESOURCE
               type: neutron.port
       scenarios:
           - condition:  host [contains] instance AND switch [connected] host AND switch [has] network AND port [attached] network AND NOT instance [connected] port
             actions:
                  - raise_alarm:
                      target: instance
                      alarm_name: instance_mem_performance_problem
                      severity: WARNING

### 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:
>         version: 3
>         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
>     entities:
>         host:
>             category: RESOURCE
>             type: nova.host
>         instance:
>             category: RESOURCE
>             type: nova.instance
>         stack:
>             category: RESOURCE
>             type: heat.stack
>         stack_alarm:
>             category: ALARM
>             name: stack_high_mem_load
>     scenarios:
>         - condition:  host [contains] instance AND stack_alarm [on] stack AND NOT instance [attached] stack
>           actions:
>                - set_state:
>                    state: available
>                    target: instance

this page last updated: 2026-01-23 22:59:33

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