Getting Started with Argo Events

Previously, we introduced how to install Argo Workflow and trigger tasks. In this article, we focus on a new tool:

What is ArgoEvents?

Argo Events is an event-driven Kubernetes workflow automation framework. It supports over 20 different event sources (e.g., webhooks, S3 drops, cronjobs, message queues such as Kafka, GCP PubSub, SNS, SQS, etc.).

Features:

Supports events from over 20 event sources and more than 10 trigger types.
Enables customization of business-level constraints for workflow automation.
Manages everything from simple, linear, real-time workflows to complex, multi-source event scenarios.
Complies with the CloudEvents specification.

Components:

EventSource (similar to a gateway; sends messages to the event bus)
EventBus (event message queue; implemented using high-performance distributed messaging middleware NATS — note that NATS has ceased maintenance after 2023, so architectural changes may be expected in the future)
EventSensor (subscribes to the message queue, parameterizes events, and filters them)

Deploying ArgoEvents

Deploy argo-events:

1
2

kubectl create ns argo-events
kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/v1.2.3/manifests/install.yaml

Deploy argo-eventbus:

`1`	`kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/eventbus/native.yaml`

RBAC Account Authorization

Create `operate-workflow-sa` account

Grant operate-workflow-sa permission to create Argo Workflows within the argo-events namespace — required for EventSensor to automatically create workflows later.

apiVersion: v1
kind: ServiceAccount
metadata:
  namespace: argo-events
  name: operate-workflow-sa
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: operate-workflow-role
  namespace: argo-events
rules:
  - apiGroups:
      - argoproj.io
    verbs:
      - "*"
    resources:
      - workflows
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: operate-workflow-role-binding
  namespace: argo-events
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: operate-workflow-role
subjects:
  - kind: ServiceAccount
    name: operate-workflow-sa
    namespace: argo-events

Create `workflow-pods-sa` account

Grant workflow-pods-sa permission to create pods via workflows within the argo-events namespace.

apiVersion: v1
kind: ServiceAccount
metadata:
  namespace: argo-events
  name: workflow-pods-sa
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: workflow-pods-role
rules:
  - apiGroups:
      - ""
    verbs:
      - "*"
    resources:
      - pods
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: workflow-pods-role-binding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: workflow-pods-role
subjects:
  - kind: ServiceAccount
    name: workflow-pods-sa
    namespace: argo-events

Automating Task Triggers with ArgoEvents

Start an event source to receive requests:

`1`	`kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/event-sources/webhook.yaml`

Note: The name field in the event source is example. You must specify this exact name when creating a sensor in production environments.

Create a webhook-based sensor to consume requests:

apiVersion: argoproj.io/v1alpha1
kind: Sensor
metadata:
  name: webhook
spec:
  template:
    serviceAccountName: operate-workflow-sa
  dependencies:
    - name: test-dep
      eventSourceName: webhook
      eventName: example
  triggers:
    - template:
        name: webhook-workflow-trigger
        k8s:
          group: argoproj.io
          version: v1alpha1
          resource: workflows
          operation: create
          source:
            resource:
              apiVersion: argoproj.io/v1alpha1
              kind: Workflow
              metadata:
                generateName: webhook-
              spec:
                serviceAccountName: workflow-pods-sa
                entrypoint: whalesay
                arguments:
                  parameters:
                  - name: message
                    # Value will be overridden by payload from test-dep
                    value: hello world
                templates:
                - name: whalesay
                  inputs:
                    parameters:
                    - name: message
                  container:
                    image: docker/whalesay:latest
                    command: [cowsay]
                    args: ["{{inputs.parameters.message}}"]
          parameters:
            - src:
                dependencyName: test-dep
              dest: spec.arguments.parameters.0.value

Reference: https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/sensors/webhook.yaml

Forward local requests to remote:

`1`	`kubectl -n argo-events port-forward <name-of-event-source-pod> <local port>:12000`

Send data to the event source:

`1`	`curl -d '{"message":"ok"}' -H "Content-Type: application/json" -X POST http://localhost:12000/example`

Now, you can automate workflow task creation using ArgoEvents.