docs: add KeptnTaskDefinition tutorial (#2121)

Signed-off-by: Adam Gardner <26523841+agardnerIT@users.noreply.github.com>
Signed-off-by: realanna <anna.reale@dynatrace.com>
Co-authored-by: realanna <anna.reale@dynatrace.com>

docs/content/en/docs/tutorials/add-tasks.md

@@ -15,9 +15,206 @@ When Keptn is successfully monitoring your deployments, it can also run arbitrar
 - pre-deployment (before the pod is scheduled) and
 - post-deployment (after the post is scheduled)
 
-Go to the [pre and post deployment checks page](../implementing/integrate#pre--and-post-deployment-checks) to find out more.
+> Pre and post deployments can also run on a KeptnApp level.
+> See [annotations to KeptnApp](../implementing/integrate/_index.md#annotations-to-keptnapp)
 
-_!
-TODO: Move the content from the above page to here.
-Help us improve the Keptn documentation by
-[opening an issue](https://github.com/keptn/lifecycle-toolkit/issues/new) to fix this documentation !_
+## Prerequisites: Deploy webhook sink
+
+During this exercise, you will configure Keptn to trigger a webhook before and after a deployment has successfully completed.
+
+For demo purposes, a place is required to send those request.
+Install the [open source webhook.site tool](https://github.com/webhooksite/webhook.site/tree/master/kubernetes) now.
+
+This will provide a place, on cluster, to send (and view) web requests.
+
+> Note: If you have your own endpoint, you can skip this step.
+
+```shell
+kubectl apply -f https://raw.githubusercontent.com/webhooksite/webhook.site/master/kubernetes/namespace.yml
+kubectl apply -f https://raw.githubusercontent.com/webhooksite/webhook.site/master/kubernetes/redis.deployment.yml
+kubectl apply -f https://raw.githubusercontent.com/webhooksite/webhook.site/master/kubernetes/laravel-echo-server.deployment.yml
+kubectl apply -f https://raw.githubusercontent.com/webhooksite/webhook.site/master/kubernetes/webhook.deployment.yml
+kubectl apply -f https://raw.githubusercontent.com/webhooksite/webhook.site/master/kubernetes/service.yml
+```
+
+Wait until all pods are running in the `webhook` namespace then port-forward and view the webhook sink page:
+
+```shell
+kubectl -n webhook wait --for=condition=Ready pods --all
+kubectl -n webhook port-forward svc/webhook 8084
+```
+
+Open a browser and go to `http://localhost:8084`
+
+You should see a page like this with a unique URL (your ID will be different).
+
+![webhook.site page](assets/webhook.site.1.png)
+
+Make a note of that unique URL.
+
+### Verify Webhook Sink
+
+Open a new browser table and go to your unique URL.
+The page should remain blank, but when toggling back to `http://localhost:8084`, you should see a new entry.
+
+Every request sent to that unique URL will be logged here.
+
+![webhook.site entry](assets/webhook.site.2.png)
+
+## Add a Post Deployment Task
+
+Add a task which will trigger after a deployment.
+
+Change `UUID` to whatever value you have.
+Apply this manifest:
+
+```yaml
+---
+apiVersion: lifecycle.keptn.sh/v1alpha3
+kind: KeptnTaskDefinition
+metadata:
+  name: send-event
+  namespace: keptndemo
+spec:
+  retries: 0
+  timeout: 5s
+  container:
+    name: curlcontainer
+    image: curlimages/curl:latest
+    args: [
+        '-X',
+        'POST',
+        'http://webhook.webhook.svc.cluster.local:8084/YOUR-UUID-HERE',
+        '-H',
+        'Content-Type: application/json',
+        '-d',
+        '{ "from": "keptn send-event" }'
+    ] 
+```
+
+### Verify it works
+
+Verify that the KeptnTaskDefinition above actually works.
+
+Trigger an on-demand task execution to verify that the job and pod function correctly.
+
+In the following steps we will have Keptn orchestrate this for us automatically.
+
+Apply this manifest:
+
+```yaml
+---
+apiVersion: lifecycle.keptn.sh/v1alpha3
+kind: KeptnTask
+metadata:
+  name: runsendevent1
+  namespace: keptndemo
+spec:
+  taskDefinition: send-event
+  context:
+    appName: "my-test-app"
+    appVersion: "1.0.0"
+    objectType: ""
+    taskType: ""
+    workloadName: "my-test-workload"
+    workloadVersion: "1.0.0"
+```
+
+If it works, `kubectl -n keptndemo get jobs` should show:
+
+```shell
+NAME                  COMPLETIONS   DURATION   AGE
+runsendevent1-*****   1/1           6s         2m
+```
+
+`kubectl -n keptndemo get pods` will show the successfully executed pod.
+
+The webhook sync should show this:
+
+![webhook sync](assets/webhook.site.3.png)
+
+Incidentally, this is exactly how you can use Keptn with [applications deployed outside of Kubernetes](../implementing/tasks-non-k8s-apps.md).
+
+> Note: If you want to trigger this multiple times, you must change the KeptnTask name.
+>
+> For example, by changing `runsendevent1` to `runsendevent2`
+
+## Ask Keptn to trigger task after Deployment
+
+Annotate the demo application `Deployment` manifest to have Keptn automatically trigger the task after every deployment.
+
+Recall the `Deployment` from the [getting started guide](../getting-started/_index.md#step-3-deploy-demo-application).
+
+Add a new label so the `labels` section looks like this:
+
+```yaml
+...
+labels:
+    app.kubernetes.io/part-of: keptndemoapp
+    app.kubernetes.io/name: nginx
+    app.kubernetes.io/version: 0.0.2
+    keptn.sh/post-deployment-tasks: "send-event"
+...
+```
+
+Increase the version number to `0.0.2` and re-apply the manifest.
+
+Here is a full version of the new YAML:
+
+```yaml
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment
+  namespace: keptndemo
+  labels:
+    app.kubernetes.io/name: nginx
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: nginx
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/part-of: keptndemoapp
+        app.kubernetes.io/name: nginx
+        app.kubernetes.io/version: 0.0.2
+        keptn.sh/post-deployment-tasks: "send-event"
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:1.14.2
+        ports:
+        - containerPort: 80
+```
+
+> Best Practice: Start with post deployment tasks.
+> Pre-deployment tasks can potentially block deployments (see below).
+
+### What Happens Next?
+
+1. The deployment will be applied
+1. When the pods are running, Keptn will automatically create a `KeptnTask` resource for version `0.0.2` of this KeptnApp
+1. The `KeptnTask` will create a Kubernetes Job
+1. The Kubernetes Job will create a Pod
+1. The pod will run curl and send a new event to the event sink
+
+### Pre-deployment Tasks
+
+Keptn Tasks can also be executed pre-deployment (before hte pods are scheduled).
+Do this by using the `keptn.sh/pre-deployment-tasks` label.
+
+> Note: If a pre-deployment task fails, the pod will remain in a Pending state.
+
+## Further Information
+
+There is a lot more you can do with KeptnTasks.
+See [pre and post deployment checks page](../implementing/integrate#pre--and-post-deployment-checks) to find out more.
+
+## What's next?
+
+Keptn can also run pre and post deployment SLO evaluations.
+
+Continue the Keptn learning journey by adding evaluations.