Knative Eventing Kogito

These components are ALPHA

Kogito is a platform to build cloud-native business automation services. It has a built-in engine able to run BPMN, Rules, DMN, and Serverless Workflows services.

The Knative Eventing Kogito is a way to have your Kogito Services in the Knative Eventing platform.

This project is under active development. To know more about it, please see our roadmap.

To learn more about Knative, please visit the Knative docs repository.

If you are interested in contributing, see CONTRIBUTING.md and DEVELOPMENT.md.

Kogito Source

You can deploy a Kogito service to act as a source of events, meaning that your business automation service can produce events targeting any addressable service within the platform.

Published event types and attributes

Events published by the Kogito Source are highly related to the type of service you create with Kogito. Usually, the event that the service produces is tied to the business application domain.

Serverless Workflows and BPMN Process

If you have a Serverless Workflow definition that produces an "Order" event, your data will reflect that structure. See the excerpt below:

id: shippinghandling
name: Shipping Handling
start: ShippingHandling
version: "1.0"
events:
  - kind: produced
    name: InternationalShippingOrder
    type: internationalShipping
    source: internationalShipping
  - kind: produced
    name: DomesticShippingOrder
    type: domesticShipping
    source: domesticShipping
states:
  - name: ShippingHandling
    type: switch
    dataConditions:
      - condition: "{{ $.[?(@.country == 'US')] }}"
        transition: DomesticShipping
      - condition: "{{ $.[?(@.country != 'US')] }}"
        transition: InternationalShipping
  - name: DomesticShipping
    type: inject
    data:
      shipping: "domestic"
    end:
      produceEvents:
        - eventRef: DomesticShippingOrder
  - name: InternationalShipping
    type: inject
    data:
      shipping: "international"
    end:
      produceEvents:
        - eventRef: "InternationalShippingOrder"

In this example, the Kogito Serverless Workflow service will produce either a DomesticShippingOrder or an InternationalShippingOrder, depending on the data processed by the workflow.

The developer of the workflow defines the data structure of the event. In this example, you can check the domain model in this repository. The domain is based on the order model sent by the main workflow.

An example of a CloudEvent produced by this service looks like this one:

cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: internationalShipping
  source: /process/shippinghandling
  id: d557fad8-81b5-482a-b981-5ecb267a92f9
  time: 2021-04-13T20:40:38.431677Z
Extensions,
  kogitoparentprociid: f12e91c0-8980-40b6-a49b-3c35ce435718
  kogitoprocid: shippinghandling
  kogitoprocinstanceid: ba57743d-521f-41f2-864a-a7b3f68d35af
  kogitorootprocid: orderworkflow
  kogitorootprociid: f12e91c0-8980-40b6-a49b-3c35ce435718
  kogitousertaskist: 1
Data,
  {"id":"f0643c68-609c-48aa-a820-5df423fa4fe0","country":"Brazil","total":10000,"description":"iPhone 12","fraudEvaluation":true,"shipping":"international"}

CloudEvents Structure

This is the structure of a produced CloudEvent:

Attribute	Value	Notes
type	Serverless Workflow: it takes the type defined in the workflow event definition BPMN: uses the message trigger name defined in the process
source	BPMN and Serverless Workflow have a constant /process/ followed by the BPMN process id or workflow id, respectively.
id	An unique generated ID
data	Contains the domain model of the event produced by the service. It depends on the business model defined by the developer.
extensions	CloudEvent extensions that carry Kogito engine data related to the workflow instance, such as the instance id of the workflow.	All extensions produced by the service start with kogito. See the table below for a list of all extensions that the Kogito Eventing supports.
datacontenttype	application/cloudevents+json	See the CloudEvents spec reference for this media type

Following the possible CloudEvents extensions that can be added to the produced events:

Extension	Name	Notes
kogitoprocinstanceid	Process Instance ID	Generated ID for a Serverless Workflow or BPMN instance
kogitoprocrefid	Process Reference ID
kogitoprocist	Process Instance State
kogitoprocid	Process ID	Identification of the process. For Serverless Workflows, it's the "workflow ID" attribute in the definition
kogitoparentprociid	Parent Process Instance ID	Identification of the parent process or workflow
kogitorootprociid	Root Process Instance ID	Identification of the root instance process or workflow
kogitorootprocid	Root Process ID	Identification of the root process or workflow. Subflows will have this attribute set to the root workflow ID.
kogitoprocstartfrom	Process Start from Node	ID of the node where the process or workflow started from.
kogitousertaskiid	User Task Instance ID	Identification for BPMN User Task Instances.
kogitousertaskist	User Task Instance State	ID of the User Task instance.
kogitoaddon	Kogito Add-ons	Collection of Kogito Add-ons used by this process or workflow instance.

Please visit our documentation to know more about creating your Kogito BPMN or Serverless Workflow with Knative Eventing.

Samples

In the examples directory, you will find some examples to get started with Kogito Eventing. To name a few:

• Order processing workflow: a small service capable of consuming an event and produce different outputs based on the contents of the order domain
• Camel Telegram: Redirect your events to a Telegram bot chat

Installation

How to install the Kogito Source in your cluster.

Prerequisites

Before installing the Knative Eventing Kogito Source, you must meet the following prerequisites:

1. You have administrative privileges in the target cluster
2. You have installed Knative Eventing and Serving (or have OpenShift Serverless Platform available)
3. (Optionally) You have installed the Kogito Operator

Installation steps

You can install the source using kubectl CLI:

VERSION=1.2.0
kubectl apply -f https://github.com/knative-sandbox/eventing-kogito/releases/download/knative-v${VERSION}/kogito.yaml

Replace the VERSION variable with the desired target version.

Note that Kogito Eventing is only available from version 0.26.0.

By running the above command you will create the namespace knative-kogito in your cluster and all the resources necessary to run the Kogito Source:

kubectl get pods -n knative-kogito

NAME                                        READY   STATUS    RESTARTS   AGE
kogito-source-controller-7689d9dc6d-4l5hv   2/2     Running   1          86m
kogito-source-webhook-54b7c87ff9-5r46h      1/1     Running   0          127m

Now you can start deploying the examples!

Using the event source

Deploying the Kogito Event Source

1. Deploy a Knative Sink to consume the events produced by your Kogito Service
2. Create your Kogito project locally. You can use our guide for Knative Eventing or Serverless Workflow.
3. Build the image with your project. See an example here.
4. Deploy the application on Kubernetes either as a Knative Service or a regular Deployment.
5. Create the Kogito Source CR. See this example to be used as a reference to create your own.
6. Use kubectl to deploy your source: kubectl apply -f <path to the source>.yaml

Verifying deployed sources

Having deployed your sources you can easily list them and check their status with the following command:

kubectl get kogitosources

You should see a listing like this one:

NAME                      READY   REASON   SINK                                                        AGE
kogito-order-processing   True             http://kogito-channel-kn-channel.kogito.svc.cluster.local   31s

The READY field gives a clue about the general status of the source.

Behind the curtains, Knative Eventing Kogito will inject the environment variables with information about the Sink to your Kogito application.

The source is ready to produce events to the sink defined in the service.

Additional Resources

• Kogito Official Documentation
• Blog: Orchestrating Events with Knative and Kogito

Roadmap

To learn more about future features, check our Roadmap.