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