01-introduction.md

# Introduction

In the tutorials, we will cover every aspect of Argo Events and demonstrate how
you can leverage these features to build an event driven workflow pipeline. All
the concepts you will learn in this tutorial and subsequent ones can be applied
to any type of event-source.

## Prerequisites

- Follow the installation guide to set up the Argo Events.
- Make sure to configure Argo Workflow controller to listen to workflow objects created in `argo-events` namespace.
  (See [this](https://github.com/argoproj/argo-workflows/blob/master/docs/managed-namespace.md) link.)
  The Workflow Controller will need to be installed either in a cluster-scope configuration (i.e. no "--namespaced" argument) so that it has visibility to all namespaces, or with "--managed-namespace" set to define "argo-events" as a namespace it has visibility to. To deploy Argo Workflows with a cluster-scope configuration you can use this installation yaml file:

        kubectl apply -n argo -f https://raw.githubusercontent.com/argoproj/argo-workflows/master/manifests/install.yaml

- Make sure to read the concepts behind
  [eventbus](https://argoproj.github.io/argo-events/concepts/eventbus/).
  [sensor](https://argoproj.github.io/argo-events/concepts/sensor/).
  [event source](https://argoproj.github.io/argo-events/concepts/event_source/).
- Follow the [instruction](https://github.com/argoproj/argo-events/tree/master/examples) to create a Service Account `operate-workflow-sa` with proper privileges, and make sure the Service Account used by Workflows (here we use `default` in the tutorials for demonstration purpose) has proper RBAC settings.

## Get Started

We are going to set up a sensor and event-source for webhook. The goal is to trigger an Argo workflow upon an HTTP Post request.

- Let' set up the eventbus.

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

- Create the webhook event source.

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

- Create the webhook sensor.

        kubectl -n argo-events apply -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/sensors/webhook.yaml

If the commands are executed successfully, the eventbus, event-source and sensor pods will get created. You will also notice that a service is created for the event-source.

- Expose the event-source pod via Ingress, OpenShift Route or port forward to consume requests over HTTP.

        kubectl -n argo-events port-forward <event-source-pod-name> 12000:12000

- Use either Curl or Postman to send a post request to the
`http://localhost:12000/example`.

        curl -d '{"message":"this is my first webhook"}' -H "Content-Type: application/json" -X POST http://localhost:12000/example

- Now, you should see an Argo workflow being created.

        kubectl -n argo-events get wf

- Make sure the workflow pod ran successfully.

        _________________________________________
        / {"context":{"type":"webhook","specVersi \
        | on":"0.3","source":"webhook","e |
        | ventID":"38376665363064642d343336352d34 |
        | 3035372d393766662d366234326130656232343 |
        | 337","time":"2020-01-11T16:55:42.996636 |
        | Z","dataContentType":"application/json" |
        | ,"subject":"example"},"data":"eyJoZWFkZ |
        | XIiOnsiQWNjZXB0IjpbIiovKiJdLCJDb250ZW50 |
        | LUxlbmd0aCI6WyIzOCJdLCJDb250ZW50LVR5cGU |
        | iOlsiYXBwbGljYXRpb24vanNvbiJdLCJVc2VyLU |
        | FnZW50IjpbImN1cmwvNy41NC4wIl19LCJib2R5I |
        | jp7Im1lc3NhZ2UiOiJ0aGlzIGlzIG15IGZpcnN0 |
        \ IHdlYmhvb2sifX0="}                      /
         -----------------------------------------
            \
             \
              \
                            ##        .
                      ## ## ##       ==
                   ## ## ## ##      ===
               /""""""""""""""""___/ ===
          ~~~ {~~ ~~~~ ~~~ ~~~~ ~~ ~ /  ===- ~~~
               \______ o          __/
                \    \        __/
                  \____\______/

<b>Note:</b> You will see the message printed in the workflow logs contains both
the event context and data, with data being base64 encoded. In later sections,
we will see how to extract particular key-value from event context or data and
pass it to the workflow as arguments.

## Troubleshoot

If you don't see the event-source and sensor pod in `argo-events` namespace,

1. Inspect the event-source.

   kubectl -n argo-events get eventsource event-source-object-name -o yaml

2. Inspect the sensor.

   kubectl -n argo-events get sensor sensor-object-name -o yaml

   and look for any errors within the `Status`.

3. Make sure the correct Role and RoleBindings are applied to the service
   account and there are no errors in both event-source and sensor controller.
4. Check the logs of event-source and sensor controller. Make sure the
   controllers have processed the event-source and sensor objects and there are
   no errors.
5. Raise an issue on GitHub or post a question on `argo-events` slack channel.