vitrage/doc/source/vitrage-template-format.rst

Vitrage Templates Format & Usage

Overview

In Vitrage we use configuration files, called "templates", to express rules regarding raising deduced alarms, setting deduced states, and detecting/setting RCA links. This page describes the format of the Vitrage templates, with some examples and open questions on extending this format. Additionally, a short guide on adding templates is presented.

Template Structure

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

metadata:
  id: <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: ...

The template is divided into three main sections:

• metadata: Contains the template identifier, and brief description of what the template does (optional)

• definitions: This section contains the atomic definitions referenced later on, for entities and relationships

  • entities – describes the resources and alarms which are relevant to the template scenario (conceptually, corresponds to a vertex in the entity graph)
  • relationships – the relationships between the entities (conceptually, corresponds to an edge in the entity graph)

• scenarios: A list of if-then scenarios to consider. Each scenario is comprised of:

  • condition – the condition to be met. This condition will be phrased referencing the entities and relationships previously defined.
  • action(s) – a list of actions to execute when the condition is met.

Condition Format

The condition which needs to be met will be phrased using the entities and relationships previously defined. An expression is either a single entity, or some logical combination of relationships. Expression can be combined using the following logical operators:

• "and" - indicates both expressions must be satisfied in order for the condition to be met.
• "or" - indicates at least one expression must be satisfied in order for the condition to be met (non-exclusive or).
• parentheses "()" - clause indicating the scope of an expression.

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

Examples

Example 1: Basic RCA and Deduced Alarm/State

The following template demonstrates

1. How to raise a deduced alarm. Specifically, if there is high CPU load on a host, raise alarm indicating CPU performance problems on all contained instances.
2. How to link alarms for purposes of root cause analysis (RCA). Specifically, if there is high CPU load on the host and CPU performance problems on the hosted instances, we link them with a "causes" relationship.
3. How to use a single template for several different scenarios.

metadata:
    id: host_high_mem_load_to_instance_mem_suboptimal
    description: when there is high memory on the host, show implications on the instances
definitions:
    entities:
        - entity:
            category: ALARM
            type: host_high_mem_load
            template_id: host_alarm # some string
        - entity:
            category: ALARM
            type: instance_mem_performance_problem
            template_id: instance_alarm
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance
    relationships:
        - relationship:
            source: host_alarm  # source and target from entities section
            target: host
            relationship_type: on
            template_id : alarm_on_host
        - 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: alarm_on_host and host_contains_instance # condition uses relationship ids
        actions:
            - action:
               action_type: raise_alarm
               properties:
                  alarm_type: instance_mem_performance_problem
                  severity: warning
               action_target:
                  target: instance # entity template_id
            - action:
               action_type: set_state
               properties:
                  state: suboptimal
               action_target:
                  target: instance # entity template_id
     scenario:
        condition: alarm_on_host and alarm_on_instance and host_contains_instance
        actions:
            - action:
               type: add_causal_relationship
               action_target:
                  source: host_alarm
                  target: instance_alarm

Example 2: Deduced state based on alarm

The following template will change the state of a resource to "ERROR" if there is any alarm of severity "CRITICAL" on it.

metadata:
    id: deduced_state_for_all_with_alarm
    description: deduced state for all resources with alarms
definitions:
    entities:
        - entity:
            category: RESOURCE
            template_id: a_resource # entity ids are any string
        - entity:
            category: ALARM
            severity: critical
            template_id: high_alarm # entity ids are any string
    relationships:
        - relationship:
            source: high_alarm
            target: a_resource
            relationship_type: on
            template_id : high_alarm_on_resource
scenarios:
    scenario:
        condition: high_alarm_on_resource
        actions:
            - action:
               action_type : set_state
               properties:
                  state: error
               action_target:
                  target: a_resource

Example 3: Deduced alarm based on state

This template will cause an alarm to be raised on any Host in state "ERROR"

Note that in this template, there are no relationships. The condition is just that the entity exists. Also note that the states and severity are case-insensitive.

metadata:
    id: deduced_alarm_for_all_host_in_error
    description: raise deduced alarm for all hosts in error
definitions:
    entities:
        - entity:
            category: RESOURCE
            type: nova.host
            state: error
            template_id: host_in_error
scenarios:
    scenario:
        condition: host_in_error
        actions:
            - action:
               action_type: raise_alarm
               properties:
                  alarm_type: host_in_error_state
                  severity: critical
               action_target:
                  target: host_in_error

Example 4: Deduced Alarm triggered by several options

This template will raise a deduced alarm on an instance, which can be caused by an alarm on the hosting zone or an alarm on the hosting host.

metadata:
    id: deduced_alarm_two_possibile_triggers
    description: deduced alarm using or in condition
definitions:
    entities:
        - entity:
            category: ALARM
            type: zone_connectivity_problem
            template_id: zone_alarm
        - entity:
            category: ALARM
            Type: host_connectivity_problem
            template_id: host_alarm
        - entity:
            category: RESOURCE
            type: nova.zone
            template_id: zone
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance
    relationships:
        - relationship:
            source: zone_alarm
            target: zone
            relationship_type: on
            template_id : alarm_on_zone
        - relationship:
            source: zone_alarm
            target: zone
            relationship_type: on
            template_id : alarm_on_host
        - relationship:
            source: zone
            target: host
            relationship_type: contains
            template_id : zone_contains_host
        - relationship:
            source: host
            target: instance
            relationship_type: contains
            template_id : host_contains_instance
scenarios:
    scenario:
        condition: (alarm_on_host and host_contains_instance) or (alarm_on_zone and zone_contains_host and host_contains_instance)
        actions:
            - action:
               action_type : raise_alarm
               properties:
                  alarm_type: instance_connectivity_problem
                  severity: critical
               action_target:
                  target: instance

Usage

Adding/removing a template

• Ensure all the templates you wish to use are placed here: <vitrage folder>/templates.
• Restart vitrage-graph.
• The template will be validated before loading. Validation errors are written to the log. Templates with validation errors are skipped.

Common parameters and their acceptable values - for writing templates

block	key	supported values	comments
entity	category	ALARM RESOURCE
entity (ALARM)	type	any string
entity (RESOURCE)	type	openstack.cluster, nova.zone, nova.host, nova.instance, cinder.volume, switch	These are for the datasources that come with vitrage by default. Adding datasources will add more supported types, as defined in the datasource transformer
action	action_type	raise_alarm, set_state, add_causal_relationship

Future support & Open Issues

Negation

We need to support a "not" operator, that indicates the following expression must not be satisfied in order for the condition to be met. "not" should apply to relationships, not entities. Then we could have a condition like

condition: host_contains_instance and not alarm_on_instance

Inequality

Consider a template that has two entities of the same category+type, say E1 and E2 both are instances like this:

metadata:
    id: two_similar_instances
definitions:
    entities:
        - entity:
            category: RESOURCE
            type: nova.host
            template_id: host
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance1
        - entity:
            category: RESOURCE
            type: nova.instance
            template_id: instance2
        ...
    relationships:
        - relationship:
            source: host
            target: instance1
            relationship_type: contains
            template_id: link1
        - relationship:
            source: host
            target: instance2
            relationship_type: contains
            template_id: link2

        ...

There are three options of how to interpret this template:

• instance1 == instance2. This option is not a reasonable one, as in this case the template can be written with only instance1
• instance1 != instance2.
• instance1 != instance2 or instance1 == instance2. In other words, either option is fine.

Thus, we need a way to distinguish between options 2 & 3 (as option 1 can be expressed by using only instance1). This can be done in two ways: 1. Introducing another logical operator "neq", to be used between expressions:

condition: (instance1 neq instance2) and...

2. Using this as a relationship type "neq":

relationship:
    source: instance1
    target: instance2
    relationship_type: neq

Cardinality

To support cardinality, for example to express we want a host to have two instances on it, we could take different approaches.

1. One approach would rely on the "neq" relationship described above. Similar to the example given in the previous section, stating that the two instances on the host are not equal is equivalent to a cardinality of two. 2. A different approach would be to expand the definition of the "relationship" clause. By default cardinality=1 (which will support backward compatibility)

For example, we might use the one of the following formats

- relationship: # option A
    source: host
    target: instance
    target_cardinality: 2 # two instances, but only one host
    relationship_type: contains
    template_id: host_contains_two_instances_A

- relationship: # option B, same as option A but split into two lines
    source: host
    target: instance
    cardinality_for: instance
    cardinality: 2
    relationship_type: contains
    template_id: host_contains_two_instances_B