Ansible Rulebook Documentation
Rulebooks contain a list of rulesets. Each ruleset within a rulebook
should have a unique name since they can post events to each other at runtime
based on the name. If a rulebook has multiple rulesets
shutting down one ruleset will shutdown all the other running rulesets.
A ruleset has the following properties:
hosts similar to Ansible playbook
default_events_ttl: time to keep the partially matched events around (default is 2 hours)
sources: A list of sources
rules: a list of rules
A ruleset should have a unique name within the rulebook, each ruleset runs
as a separate session in the Rules engine. The events and facts are kept separate
for each ruleset. At runtime, using action a ruleset can post events or facts
to itself or other rulesets in the rulebook.
The default_events_ttl takes time in the following format
default_events_ttl : nnn seconds|minutes|hours|days
e.g. default_events_ttl : 3 hours
If the rule set doesn’t define this attribute the default events ttl that is
enforced by the rule engine is 2 hours
When we start a rulebook we can optionally collect artifacts from the different hosts
if gather_facts is set to true. This host data is then uploaded to the Rules
engine as fact to be evaluated at runtime in the different rules based on the
incoming events. Each host data is stored separately in the Rules engine. To access the
host name use the fact.meta.hosts attribute. e.g.
- name: Example
- name: range
- name: r1
condition: event.i == 1
- name: "Host specific rule"
- fact.ansible_os_family == "linux"
- fact.meta.hosts == "my-host"
- event.i == 4
A ruleset must contain one or more sources, it allows you to pass configuration
parameters into the source plugin. The Source plugin can also be configured with
event filters which allow you to transform the data before passing it to the Rules
engine. The filters can also be used to limit the data that gets passed to the Rules
engine. The source plugin is started by the ansible-rulebook and runs in the
background putting events into the queue to be passed onto the Rules engine.
When the source plugin ends we automatically generate a shutdown event and the ruleset
terminates which terminates ansible-rulebook.
A ruleset must contain one or more rules. The rules are evaluated by the Rules engine.
The Rules engine will evaluate all the required conditions for a rule based on the
incoming events. If the conditions in a rule match, we trigger the actions. The actions
can run playbooks, modules, raise another event or fact to the same ruleset or a different
ruleset. A ruleset stops execution when it receives the shutdown event from either the
Source plugin or a shutdown action is invoked by one of the matching rules.
Including multiple sources
In a rulebook you can configure one or more sources, each emitting events in different format.
The condition can match events from either source
condition: event.i == 2
condition: event.payload.status == "OK"
To avoid name conflicts the source data structure can use nested keys.
If any source terminates, it shuts down the whole engine. All events from other sources may be lost.