Drools integration with Ansible Rulebook

Description

An integration layer allowing Ansible Rulebook to use Drools as rule engine for rules evaluation. Drools can be invoked from Ansible either via a REST API or natively through jpy.

Installing and Running REST API service

Prerequisites

You will need:

• Java 11+ installed
• Environment variable JAVA_HOME set accordingly
• Maven 3.8.1+ installed

When using native image compilation, you will also need:

• GraalVM 22.1.0 installed
• Environment variable GRAALVM_HOME set accordingly
• Note that GraalVM native image compilation typically requires other packages (glibc-devel, zlib-devel and gcc) to be installed too. You also need 'native-image' installed in GraalVM (using 'gu install native-image'). Please refer to GraalVM installation documentation for more details.

Compile and Run in Local Dev Mode

mvn clean install
cd drools-ansible-rulebook-integration-core-rest
mvn clean compile quarkus:dev

Package and Run in JVM mode

mvn clean install
cd drools-ansible-rulebook-integration-core-rest
java -jar target/quarkus-app/quarkus-run.jar

Package and Run using Local Native Image

Note that this requires GRAALVM_HOME to point to a valid GraalVM installation

mvn clean install
cd drools-ansible-rulebook-integration-core-rest
mvn clean package -Pnative

To run the generated native executable, generated in target/, execute

./target/drools-ansible-rulebook-integration-core-rest-1.0.2-SNAPSHOT-runner

Note: This does not yet work on Windows, GraalVM and Quarkus should be rolling out support for Windows soon.

OpenAPI (Swagger) documentation

Specification at swagger.io

You can take a look at the OpenAPI definition - automatically generated and included in this service - to determine all available operations exposed by this service. For easy readability you can visualize the OpenAPI definition file using a UI tool like for example available Swagger UI.

In addition, various clients to interact with this service can be easily generated using this OpenAPI definition.

When running in either Quarkus Development or Native mode, we also leverage the Quarkus OpenAPI extension that exposes Swagger UI that you can use to look at available REST endpoints and send test requests.

Example usage

POST /create-rules-executor

Creates a rules executor with the set of rules defined in the json payload as in the following example:

curl -X POST -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{
  "rules": [
    {"Rule": {
      "name": "R1",
      "condition": "sensu.data.i == 1",
      "action": {
        "assert_fact": {
          "ruleset": "Test rules4",
          "fact": {
            "j": 1
          }
        }
      }
    }},
    {"Rule": {
      "name": "R2",
      "condition": "sensu.data.i == 2",
      "action": {
        "run_playbook": [
          {
            "name": "hello_playbook.yml"
          }
        ]
      }
    }},
    {"Rule": {
      "name": "R3",
      "condition":{
        "any":[
          {
            "all":[
              "sensu.data.i == 3",
              "j == 2"
            ]
          },
          {
            "all":[
              "sensu.data.i == 4",
              "j == 3"
            ]
          }
        ]
      },
      "action": {
        "retract_fact": {
          "ruleset": "Test rules4",
          "fact": {
            "j": 3
          }
        }
      }
    }},
    {"Rule": {
      "name": "R4",
      "condition": "j == 1",
      "action": {
        "post_event": {
          "ruleset": "Test rules4",
          "fact": {
            "j": 4
          }
        }
      }
    }}
  ]
}' http://localhost:8080/create-rules-executor

As response it will return a simple number which is the identifier of the generated rules executor. Use this number in the URL of subsequent calls to that executor.

Note that the condition activating the rule can be a simple one, made only by one single constraint, or a nested combination of AND and OR like in R3. There all means that all conditions must be met in order to activate the rule, so it's equivalent to a AND, while any means that any of them is sufficient, equivalent to a OR.

POST /rules-executors/{id}/execute

Processes the event passed in the json payload, also executing the consequences of the rules (actions) that it activates.

curl -X POST -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{ "sensu": { "data": { "i":1 } } }' http://localhost:8080/rules-executors/1/execute

This call, other than having the side-effect of actually executing the activated rules, returns a value representing the number of executed rules.

POST /rules-executors/{id}/process

Processes the event passed in the json payload, without executing the consequences of the rules (actions), but only returning the list of rules activated by the event.

curl -X POST -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{ "sensu": { "data": { "i":1 } } }' http://localhost:8080/rules-executors/1/process

Example response:

[
  {
    "ruleName":"R1",
    "facts":{
      "sensu":{
        "data":{
          "i":1
        }
      }
    }
  }
]

Note that if the engine is used only in this way, i.e. only to evaluate rules but not to fire them, the rules actions are useless and they can be safely omitted in the json payload defining the rule set.